Chapter 21: The Knee

The knee joint is designed for mobility and stability; it functionally lengthens and shortens the lower extremity to raise and lower the body or to move the foot in space. Along with the hip and ankle, it supports the body when standing, and it is a primary functional unit in walking, climbing, running, and sitting activities.

As in the other regional chapters of the text, this chapter is divided into three primary sections. Highlights of the anatomy and function of the knee complex are reviewed in the first section of the chapter, followed by material on the management of knee disorders and surgeries. The third section includes exercise interventions for the knee region. Chapters 10 through 13 present general information on principles of management. The reader should be familiar with the material in these chapters as well as have a background in examination and evaluation in order to effectively design a therapeutic exercise program to improve knee function in patients with impairments due to injury or pathology or following surgery.

The bones of the knee joint consist of the distal femur with its two condyles, the proximal tibia with its two tibial plateaus, and the large sesamoid bone in the quadriceps tendon, the patella. It is a complex joint both anatomically and biomechanically (Fig. 21.1).¹⁰⁵ The proximal tibiofibular joint is anatomically close to the knee but is enclosed in a separate joint capsule and functions with the ankle. Therefore, the proximal tibiofibular joint is discussed in Chapter 22.

Joints of the Knee Complex

A lax joint capsule encloses two articulations: the tibiofemoral and the patellofemoral joints. Recesses from the capsule form the suprapatellar, subpopliteal, and gastrocnemius bursae. Folds or thickenings in the synovium persist from embryologic tissue in as many as 60% of individuals and may become symptomatic with microtrauma or macrotrauma.^23,131

Tibiofemoral Joint

Characteristics. The knee joint is a biaxial, modified hinge joint with two interposed menisci supported by ligaments and muscles. Anteroposterior stability is provided by the cruciate ligaments; mediolateral stability is provided by the medial (tibial) and lateral (fibular) collateral ligaments, respectively (Fig. 21.2).^37,105

• bThe convex boney partner is composed of two asymmetrical condyles on the distal end of the femur. The medial condyle is longer than the lateral condyle, which contributes to the locking mechanism at the knee.

• The concave boney partner is composed of two tibial plateaus on the proximal tibia with their respective fibro-cartilaginous menisci. The medial plateau is larger than the lateral plateau.

• The menisci improve the congruency of the articulating surfaces. They are connected to the tibial condyles and capsule by the coronary ligaments, to each other by the transverse ligament, and to the patella via the patellomeniscal ligaments.¹⁰⁵ Anterior and posterior meniscofemoral ligaments also may be present connecting the lateral meniscus to the femur.¹⁰² The medial meniscus is firmly attached to the joint capsule as well as to the medial collateral ligament, anterior and posterior cruciate ligaments, and semimembranosus muscle. The lateral meniscus attaches to the posterior cruciate ligament and the tendon of the popliteus muscle through capsular connections.¹⁰⁵ Because of the relatively secure attachment of the medial meniscus compared to the lateral meniscus (see Fig. 21.2), it has a greater chance of sustaining a tear when there is a lateral blow to the knee.

Arthrokinematics. Joint mechanics are affected by open-and closed-chain positions of the extremity and are summarized in Box 21.1. Rotation occurs as the knee flexes and extends.

• With motions of the tibia while in a nonweight-bearing, open kinematic chain, the concave plateaus slide in the same direction as the bone motion. Terminal extension results in the tibia rotating externally on the femur; with flexion, the tibia rotates internally.

• With motions of the femur on a fixated tibia while in a weight-bearing, closed kinematic chain, the convex condyles slide in the direction opposite to the bone motion.

Screw-home mechanism. The rotation that occurs between the femoral condyles and the tibia during the final degrees of extension is called the locking, or screw-home, mechanism. When the tibia is fixed with the foot weight bearing on the ground, terminal extension results in the femur rotating internally (the medial condyle slides farther posteriorly than the lateral condyle). Concurrently, the hip moves into extension. Tautness in the iliofemoral ligament, which occurs with hip extension, reinforces the medial rotation of the femur. As the knee is unlocked, the femur rotates laterally. Unlocking of the knee occurs indirectly with hip flexion and directly from action of the popliteus muscle. An individual who lacks full hip extension (hip flexion contracture) cannot stand upright and lock the knee, thus lacking this passive stabilizing function.

Patellofemoral Joint

Characteristics. The patella is a sesamoid bone in the quadriceps tendon. It articulates with the intercondylar (trochlear) groove on the anterior aspect of the distal portion of the femur. Its articulating surface is covered with smooth hyaline cartilage. The patella is embedded in the anterior portion of the joint capsule and is connected to the tibia by the ligamentum patellae. Many bursae surround the patella.¹⁰⁵

Mechanics. As the knee flexes, the patella enters the intercondylar groove with its inferior margin making first contact and then slides caudally along the groove. With extension, the patella slides superiorly. If patellar movement is restricted, it interferes with the range of knee flexion and may contribute to an extensor lag with active knee extension.²⁸³

Patellar Function

The primary function of the patella is to increase the moment arm of the quadriceps muscle in its function to extend the knee. It also redirects the forces exerted by the quadriceps.

Patellar Alignment

The alignment of the patella in the frontal plane is influenced by the line of pull of the quadriceps muscle group and by its attachment to the tibial tubercle via the patellar tendon. The result of these two forces is a bowstring effect on the patella, causing it to track laterally. One method of describing the bowstring effect is to measure the Q-angle. The Q-angle is the angle formed by two intersecting lines: one from the anterior superior iliac spine to the midpatella, the other from the tibial tubercle through the midpatella (Fig. 21.3).^105,173 A normal Q-angle, which tends to be greater in women than men, is 10° to 15°.

Forces Maintaining Alignment

In addition to the boney restraints of the trochlear groove (femoral sulcus), the patella is stabilized by passive and dynamic (muscular) restraints. The superficial portion of the extensor retinaculum, to which the vastus medialis and vastus lateralis muscles have an attachment, provides dynamic stability in the transverse plane. The medial and lateral patellofemoral ligaments, which attach to the adductor tubercle medially and iliotibial band laterally provide passive restraints to the patella in the transverse plane.¹⁰⁵ Longitudinally, the medial and lateral patellotibial ligaments and patellar tendon fixate the patella inferiorly against the active pull of the quadriceps muscle superiorly (Fig. 21.4).

Patellar Malalignment and Tracking Problems

Malalignment and tracking problems of the patella may be caused by several factors that may or may not be interrelated.⁹⁷

Increased Q-angle. With an increased Q-angle, there may be increased pressure of the lateral facet against the lateral femoral condyle when the knee flexes during weight bearing. Structurally, an increased Q-angle occurs with a wide pelvis, femoral anteversion, coxa vara, genu valgum, and laterally displaced tibial tuberosity. Lower extremity motions in the transverse plane that may increase the Q-angle are external tibial rotation, internal femoral rotation, and a pronated subtalar joint. Dynamic knee valgus (see Fig. 21.9), where the knee joint center moves medially relative to the foot during weight-bearing activities, also increases the Q-angle.^227,228

Muscle and fascial tightness. A tight iliotibial (IT) band and lateral retinaculum prevent medial gliding of the patella. Tight ankle plantarflexors result in pronation of the foot when the ankle dorsiflexes, causing medial torsion of the tibia and functional lateral displacement of the tibial tuberosity in relationship to the patella.¹⁵⁹ Tight rectus femoris and hamstring muscles may affect the mechanics of the knee, leading to compensations.¹⁶⁶

Hip muscle weakness. Weakness of the hip abductors and external rotators may result in adduction of the femur and valgus at the knee and contribute to increased medial rotation of the femur observed under loaded weight bearing in subjects with patellofemoral pain syndrome.^121,189

Lax medial capsular retinaculum or an insufficient VMO muscle. The vastus medialis obliquus (VMO) muscle may be weak from disuse or inhibited because of joint swelling or pain, leading to poor medial stability.²⁷² Poor timing of its contraction, which alters the ratio of firing between the VMO and vastus lateralis (VL) muscle, may lead to an imbalance of forces.^245,292 It has been suggested that weakness or poor timing of VMO contractions increases the lateral drifting of the patella. However, a recent systematic review and meta-analysis indicated that, although there is a trend demonstrating delayed onset of VMO relative to VL contractions in subjects with patellofemoral pain, evidence supporting this idea is difficult to access due to unexplained heterogeneity in the studies reviewed.⁴²

Patellar Compression

Patellar contact. The posterior surface of the patella has several facets. It is not completely congruent as it articulates with the trochlear groove on the femur. When the knee is in complete extension (0°), the patella is superior to the trochlear groove. By 15° of flexion, the inferior border of the patella begins to articulate with the superior aspect of the groove. As the knee flexes, the patella slides distally in the groove, and more surface area comes in contact. Beyond 60° there is controversy as to whether the contact area continues to increase, levels off, or decreases.^96,97 In addition, as the knee flexes past 90°, the quadriceps tendon comes in contact with the trochlear groove as the patella slides inferiorly.

Compression forces. In full extension, because there is minimal to no contact of the patella with the trochlear groove, there is no compression of the articular surfaces. Furthermore, because the femur and tibia are almost parallel, the line of pull of the quadriceps muscle and patellar tendon causes a very small resultant compressive load. The resultant force of the quadriceps and patellar tendon forces rises as the knee flexes, but there is also greater surface area of the patella in contact with the groove to dissipate this force. The joint reaction force on the articular surface rises rapidly between 30° and 60°. There is controversy as to the extent of joint reaction forces in greater degrees of flexion.

• During squatting, the joint reaction force continues to rise until 90° and then levels off or decreases because the quadriceps tendon begins making contact with the trochlear groove and therefore dissipates some of the force.⁹⁶

• In an open-chain, nonweight-bearing exercise with a free weight on the distal leg, the greatest joint reaction force in the patellofemoral articulation occurs at around 30° of flexion.⁹⁶ This is more likely due to the changing moment arm of the weight rather than the resultant force of the quadriceps and patellar tendons. In an open-chain with variable resistance, the peak stress is at 60° and peak compression is at 75°.⁶⁷

• An increased Q-angle causes increased lateral facet pressure as the knee flexes.²²⁸

Muscle Function

Knee Extensor Muscle Function

The quadriceps femoris muscle group is the only muscle crossing anterior to the axis of the knee and is the prime mover for knee extension. Other muscles that can act to extend the knee require the foot to be fixated, creating a closed chain. In this situation, the hamstrings and the soleus muscles can cause or control knee extension by pulling the tibia posteriorly.

Closed-chain function. During standing and the stance phase of gait, the knee is an intermediate joint in a closed chain. The quadriceps muscle controls the amount of flexion at the knee and also causes knee extension through reverse muscle pull on the femur. In the erect posture, when the knee is locked, the quadriceps need not function when the gravity line falls anterior to the axis of motion. In this case, tension in the hamstring and gastrocnemius tendons supports the posterior capsule.

Patella. The patella improves the moment arm of the extensor force by increasing the distance of the quadriceps tendon from the knee joint axis. Its greatest effect on the leverage of the quadriceps is during extension of the knee from 60° to 30° and rapidly diminishes from 15° to 0° of extension.^99,105

Torque. The peak torque of the quadriceps muscle occurs between 70° and 50°.³⁴ The physiological advantage of the quadriceps rapidly decreases during the last 15° of knee extension because of its shortened length. This, combined with its decreased moment arm in the last 15°, requires the muscle to significantly increase its contractile force when large demands are placed on the muscle during terminal extension.⁹⁹

• During standing, assistance for extension comes from the hamstring and soleus muscles as well as from the mechanical locking mechanism of the knee. In addition, the anterior cruciate ligament and the pull of the hamstring muscle group counter the anterior translation force of the quadriceps muscle.^76,164

• During open-chain knee extension exercises in the sitting or supine position, when the resistive force is maximum in terminal extension because of the moment arm of the resistance, a relatively strong contraction of the quadriceps muscle is required to overcome the physiological and mechanical disadvantages of the muscle to complete the final 15° of motion.⁹⁹ However, it is worth mentioning that the compressive loads on the patella also decrease in terminal extension because of its superior location with respect to the trochlear groove and the resultant force of the line of pull of the quadriceps and patellar tendon.

• The therapist needs to be aware of the effect of the resistance and where in the range of motion the muscle is being challenged. During open-chain, nonweight-bearing exercises with fixed resistance, when the resistance torque challenges the quadriceps in terminal extension, there is little challenge midrange where the muscle is capable of generating greater tension.

Knee Flexor Muscle Function

The hamstring muscles are the primary knee flexors and also influence rotation of the tibia on the femur. Because the hamstrings are two-joint muscles, they contract more efficiently when they are simultaneously lengthened over the hip (during hip flexion) as they flex the knee. During closed-chain, weight-bearing activities, the hamstring muscles can assist with knee extension by pulling on the tibia.

• The gastrocnemius muscle also can function as a knee flexor, but its prime function at the knee during weight bearing is to support the posterior capsule against hyperextension forces.

• The popliteus muscle supports the posterior capsule and acts to unlock the knee.

• The pes anserinus muscle group (sartorius, gracilis, semitendinosus) provides medial stability to the knee and affects rotation of the tibia in a closed chain.

Dynamic Stability of the Knee

Because of the incongruity of the femoral condyles and tibial plateaus, there is little stability from the boney architecture. The cruciate and collateral ligaments provide significant passive stability in the various ranges of joint motion. Dynamic stability is the ability of a joint to remain stable in the presence of rapidly shifting loads during motion.¹¹⁸ Dynamic stability involves motor control of the neuromuscular system to coordinate muscle activity around the joint. The complex feedforward and feedback responses mediated by the central nervous system modulate muscle stiffness and are important for providing dynamic knee stability under varying loads and stresses imposed on the joint structures.³⁰⁴ As summarized in a clinical commentary by Williams,³⁰⁴ clinical and scientific evidence is accumulating to substantiate exercise programs designed for the purpose of developing dynamic stability of the knee—that is, to improve control of the knee via neuromuscular responses in order to reduce knee ligament stress and the risk of injury during high-intensity activities.

The Knee and Gait

During the normal gait cycle, the knee goes through a range of 60° (0° extension at initial contact or heel strike to 60° at the end of initial swing). There is some medial rotation of the femur as the knee extends at initial contact and just prior to heel-off.^105,207,222

Muscle Control of the Knee During Gait

Stability during the gait cycle is efficiently controlled by the normal function of the muscles that attach at the knee.^207,222

Quadriceps. The quadriceps muscle controls the amount of knee flexion during initial contact (loading response) and then extends the knee toward midstance. It again controls the amount of flexion during preswing (heel-off to toe-off) and prevents excessive heel rise during initial swing. With loss of quadriceps function, the patient lurches the trunk anteriorly during initial contact to move the center of gravity anterior to the knee so it is stable or rotates the extremity outward to lock the knee.²⁷⁶ With fast walking, there may be excessive heel rise during initial swing.

Hamstrings. The hamstring muscles primarily control the forward swing of the leg during terminal swing. Loss of function may result in the knee snapping into extension during this period. The hamstrings also provide posterior support to the knee capsule when the knee is extended during stance. Loss of function results in progressive genu recurvatum.²⁷⁶

Soleus. The unijoint ankle plantarflexor muscles (primarily the soleus) help control the amount of knee flexion during preswing by controlling the forward movement of the tibia. Loss of function results in hyperextension of the knee during preswing (also loss of heel rise at the ankle and thus a lag or slight dropping of the pelvis on that side during the preswing phase).

Gastrocnemius. The gastrocnemius muscle provides tension posterior to the knee when it is in extension (end of loading response or foot flat and just prior to preswing or heel-off). Loss of function results in hyperextension of the knee during these periods as well as loss of plantarflexion during preswing or push-off.

Hip and Ankle Impairments

Because the knee is the intermediate joint between the hip and foot, problems in these two areas can interfere with knee function during gait. Examples include the following.

Hip flexion contractures. Inability to extend the hip prevents the knee from extending just before terminal stance (heel-off).

Length/strength imbalances. With asymmetry of length, strength, and neuromuscular control of hip and knee muscles, unbalanced forces may stress various structures of the knee, giving rise to pain during walking or running. For example, a tight tensor fasciae latae or gluteus maximus muscle increases stress on the IT band, which could lead to lateral knee pain. It could also affect tracking of the patella and lead to anterior knee pain. Weak hip external rotators and abductors result in femoral internal rotation, which creates a relative lateral displacement of the patella and subsequent patellofemoral pain.²⁷⁰ Overuse of the hamstring muscle group increases posterior translation forces on the tibia, requiring compensation in the quadriceps femoris muscle and resulting in anterior knee pain (see Chapter 20 for discussion of muscle imbalances in hip).

Foot impairments. The position and function of the foot and ankle affect the stresses transmitted to the knee. For example, with pes planus or pes valgus, there is medial rotation of the tibia and an increased bowstring effect on the patella, increasing the lateral tracking forces.

Referred Pain and Nerve Injuries

For a detailed description of referred pain patterns and peripheral nerve injuries in the knee region, see Chapter 13.

Major Nerves Subject to Injury at the Knee

The sciatic nerve divides into the tibial and common peroneal nerves just proximal to the popliteal fossa. These nerves are relatively well protected deep in the fossa.

• The common fibular (peroneal) nerve (L2–L4) becomes superficial where it winds around the fibula just below the fibular head, a common site for injury. Symptoms of sensory loss and muscle weakness are distal to that site.

• The saphenous nerve (L2–L4) is a sensory nerve that innervates the skin along the medial side of the knee and leg. It may be injured with trauma or surgery in that region, resulting in chronic pain syndromes.

Common Sources of Referred Pain

Nerve roots and tissues derived from spinal segments L3 refer to the anterior aspect, and those from S1 and S2 refer to the posterior aspect of the knee.⁵⁰ The hip joint, which is primarily innervated by L3, may refer symptoms to the anterior thigh and knee. Therapeutic exercise for the knee is beneficial only for preventing disuse of the part. Primary treatment must be directed to the source of the nerve irritation.

To make sound clinical decisions when treating patients with knee disorders, it is necessary to understand the various pathologies, surgical procedures, and associated precautions and to identify presenting structural and functional impairments, activity limitations (functional limitations), and possible participation restrictions (disabilities). In this section, common pathologies and surgical procedures are presented and related to corresponding preferred practice patterns (groupings of impairments) described in the Guide to Physical Therapist Practice³ (Table 21.1). Conservative and postoperative management of these conditions is described in this section.

Joint Hypomobility: Nonoperative Management

Common Joint Pathologies and Associated Impairments

OA and rheumatoid arthritis (RA), as well as acute joint trauma, can affect the knee articulations. In addition, decreased flexibility and adhesions develop in the joints and surrounding tissues any time the knee joint is immobilized for a period of time such as following an injury, surgery, or fracture in the related bones. Reflex inhibition and resulting weakness of the quadriceps femoris muscle occurs because of joint distention.²⁷² The etiology of arthritic and joint symptoms and general management guidelines are described in Chapter 11; this section applies that information to management of the knee joint.

Osteoarthritis (Degenerative Joint Disease)

OA, often referred to as degenerative joint disease (DJD), is the most common disease affecting weight-bearing joints. Articular cartilage destruction typically is more apparent on the medial than the lateral aspect of the knee (Fig. 21.5).

One-third of individuals older than age 65 have radiographic evidence of OA.¹⁶ Pain, muscle weakness, medial joint laxity, and limitation of joint motion affect function and lead to disability. Deformity such as genu varum commonly develops in the knees. Knee instability (the sensation of knee buckling or shifting) is also frequently reported by individuals with knee OA and significantly contributes to impaired physical function.⁷⁸

Factors such as excess weight, joint trauma, developmental deformities, weakness of the quadriceps muscle, and abnormal tibial rotation are identified as risk factors for developing OA of the knee.¹⁶

Posttraumatic arthritis of the knee occurs in response to any injury that affects the joint structures, particularly following acute ligament and meniscal tears. Joint swelling (effusion) may be immediate, indicating bleeding within the joint, or progressive (more than 4 hours to develop), indicating serous effusion. Acute symptoms include pain, limited motion, and muscle guarding. Trauma, including repetitive microtrauma, is a common cause of degenerative changes in the knee joint.

Rheumatoid Arthritis

Early-stage rheumatoid arthritis (RA) usually manifests first in the hands and feet. With progression of the disease process, the knees also may become involved. The joints become warm and swollen, and limited motion develops. In addition, a genu valgum deformity commonly develops during the advanced stages of this disease.

Postimmobilization Hypomobility

When the knee has been immobilized for several weeks or longer, such as during healing of a fracture or after surgery, the capsule, muscles, and soft tissue develop contractures, and motion becomes restricted. Adhesions may restrict caudal gliding of the patella, which limits knee flexion, and may cause pain as the patella is compressed against the femur. An extensor lag may occur with active knee extension if the patella does not glide proximally when the quadriceps muscle contracts.²⁷⁴ This usually occurs after operative repairs of some knee ligaments, when the knee is immobilized in flexion for a prolonged period.

Common Structural and Functional Impairments

• With joint involvement, the pattern of restriction at the knee is usually more loss of flexion than extension.

• When there is effusion (swelling within the joint), the joint assumes a position near 25° of flexion, the position at which there is the greatest capsular distensibility. Little motion is possible because of the swelling.

• Symptoms of joint involvement, such as distention, stiffness, pain, and reflex quadriceps inhibition, may cause extensor (quadriceps) lag in which the active range of knee extension is less than the passive range available.²⁷⁴

• Impaired balance responses also have been reported in patients with arthritis.²⁹⁵

Common Activity Limitations and Participation Restrictions (Functional Limitations and Disabilities)

• With acute symptoms and in advanced stages of degeneration, there is pain during motion, weight bearing, and gait that may interfere with work or routine household and community activities.

• There is limitation of, or difficulty controlling, weight-bearing activities that involve knee flexion, such as sitting down and rising from a chair or a commode, descending or ascending stairs, stooping, or squatting.⁷⁵

• With end-stage arthritis, physical activity is markedly curtailed with less participation in leisure activities (e.g., walking, gardening, swimming, athletic activities) and household activities (e.g., dusting, washing floors, cleaning, shopping).²⁸⁵

Joint Hypomobility: Management—Protection Phase

See Chapter 11 for general guidelines for the management of acute joint lesions and specific guidelines for OA and RA.

Control Pain and Protect the Joint

Patient education. It is important to teach the patient methods to protect the joint including bed positioning, use of splints in order to avoid deforming contractures, range-of-motion (ROM) and muscle-setting exercises to maintain mobility and promote blood flow, and safe functional activities that reduce stresses on the knee.

Functional adaptations. Instruct the patient to minimize stair-climbing, use elevated seats on commodes, and avoid deep-seated or low chairs in order to minimize stressful knee flexion ranges while bearing weight. If necessary during an acute flare of arthritis, have the patient use crutches, canes, or a walker to distribute forces through the upper extremities while walking.

Maintain Soft Tissue and Joint Mobility

Passive, active-assistive, or active ROM. Use ROM techniques within the limits of pain and available motion. The patient may be able to perform active ROM in the gravity-eliminated, side-lying position, or self-assisted ROM.

Grade I or II joint distraction and anterior/posterior glides. Apply gentle joint techniques, if tolerated, with the joint in or near resting position (25° flexion). These techniques are used to inhibit pain as well as maintain joint mobility. Stretching is contraindicated at this stage.

Maintain Muscle Function and Prevent Patellar Adhesions

Setting exercises. Perform pain-free quadriceps ("quad sets") and hamstring muscle-setting exercises with the knee in various pain-free positions, quad sets with leg raises, and submaximal closed-chain muscle setting exercises. Muscle-setting exercises are described in detail in the last section of this chapter. Quad sets may help maintain mobility of the patella when the tibiofemoral joint is immobilized and therefore are routinely taught following surgery or when the joint is immobilized.

Joint Hypomobility: Management—Controlled Motion and Return to Function Phases

As joint effusion decreases and joint tissues are able to tolerate increased stresses, the goals of treatment change to deal with the impairments that interfere with functional activities. The patient is progressed through controlled motion exercises and activities that focus on safely returning to desired functional outcomes.

Educate the Patient

• Inform the patient about his or her condition, what to expect regarding recovery, and how to protect the joints.

• Teach the patient safe exercises to do at home, how to progress them, and how to modify them if symptoms are exacerbated by the disease or from overuse. Exercises that include specifically designed strengthening, stretching, ROM, and use of a stationary bicycle have been shown to improve functional outcomes in patients with OA in a home exercise program.⁵⁸ It is important to emphasize that maintaining strength in the supporting muscles helps protect and stabilize the joint and that balance exercises help reduce the incidence of falls.

• Instruct the patient to perform active ROM and muscle-setting techniques frequently during the day, especially prior to bearing weight, in order to reduce the painful symptoms that occur with initial weight bearing.⁷⁵

• The patient with OA or RA should be cautioned to alternate activity with rest.

Decrease Pain from Mechanical Stress

Continue use of assistive devices for ambulation, if necessary. The patient may progress to using less assistance or may ambulate for periods without assistance. Continue use of elevated seats on commodes and chairs, if needed, to reduce the mechanical stresses imposed when attempting to stand.⁷⁵

Increase Joint Play and Range of Motion

PRECAUTION: Do not increase ROM unless the patient has sufficient strength to control the motion already available. A mobile weight-bearing joint with inadequate muscle control causes impaired stability and makes lower extremity weight-bearing function difficult.

Joint mobilization. When there is loss of joint play and decreased mobility, joint mobilization techniques should be used. Apply grade III or IV sustained or oscillatory techniques to the tibiofemoral and patellofemoral articulations with the joint positioned at the end of its available range before applying the mobilization technique. (See Figures 5.49 through 5.54 and their descriptions in Chapter 5.) As ROM increases, it is important to emphasize the rotational accessory motions that accompany flexion and extension.¹²⁹

• To increase flexion, position the tibia in medial rotation and apply the posterior glide against the anterior aspect of the medial tibial plateau.

• To increase extension, position the tibia in lateral rotation and apply the anterior glide against the posterior aspect of the lateral tibial plateau.

• Medial and lateral gliding of the tibia on the femur may also be done to regain mobility for flexion and extension.

Stretching techniques. Passive and PNF stretching techniques are used to increase extensibility of the muscles and extracapsular noncontractile soft tissues that restrict knee motion. Specific techniques are described in the last section of this chapter.

PRECAUTIONS: Techniques that force the knee into flexion by using the tibia as a lever or by using strong quadriceps contractions (during a hold-relax maneuver) may exacerbate joint symptoms.

Incorporate the following to minimize joint trauma from stretching.

• Mobilize the patellofemoral and tibiofemoral joints before stretching in order to improve gliding of the joint surfaces during the stretch maneuvers.

• Apply soft tissue or friction massage to loosen adhesions or contractures prior to stretching. Include deep massage around the border of the patella.

• Modify the intensity of contraction when applying PNF stretching techniques to range-limiting muscles in order to decrease the effects of joint compression. If the hold-relax technique aggravates anterior knee pain when attempting to increase knee flexion, use the agonist contraction technique to the hamstring muscles to minimize compression from a strong quadriceps muscle contraction.

• Use low-intensity, long-duration stretches within the patient's tolerance.

Mobilization with movement. Mobilization with movement (MWM) may be applied to increase ROM and/or decrease the pain associated with movement by improving joint tracking. Mulligan¹⁹⁰ states that MWM is more effective with loss of flexion than extension. The principles of MWM are described in Chapter 5.

MWM: Lateral or Medial Glides

Patient position and procedure: Supine for extension or prone for flexion. Apply a pain-free medial or lateral glide to the tibial plateau manually or through the use of a mobilization belt. The direction of glide is often in the direction of the pain (i.e., lateral knee pain responds best to a lateral glide of the tibia and medial knee pain to a medial glide).¹⁹⁰

• While sustaining the mobilization, ask the patient to move to the end of the available pain-free range of flexion or extension.

• Add pain-free overpressure to achieve the benefit of end-range loading.

MWM: Internal Tibial Rotation for Flexion—Manual Technique

Patient position and procedure: Supine with the knee flexed to the end of its available pain-free range. Apply internal rotation mobilization to the tibia with manual pressure from one hand on the anteromedial tibial plateau simultaneously with pressure from the other hand on the posterolateral tibial plateau, posterior to the fibular head.

• Sustain the internal rotation mobilization, and ask the patient to flex the knee through the use of a mobilization belt looped around the foot. Hold the position at the end of the available pain-free range for several seconds (Fig. 21.6).

MWM: Internal Rotation for Flexion—Self-Treatment

Patient position and procedure: Standing with the foot of the involved leg on a chair and knee flexed. Position the foot such that the tibia is internally rotated. Have the patient apply internal rotation pressure against the anteromedial and posterolateral tibial plateaus and shift the weight forward to flex the knee to the end of the available pain-free range (Fig. 21.7).

Improve Muscle Performance in Supporting Muscles

Exercises identified in this section are described in detail in the last section of this chapter.

Progressive strengthening. Begin with multiple-angle isometrics to both knee flexors and extensors and active ROM exercises in open- and closed-chain positions using a moderate progression of repetitions and resistance in arcs of pain-free motion. Exercise intensity should be within the tolerance of the joint and not exacerbate symptoms.

• When performing open-chain exercises, patients experience less pain with faster speeds and lighter resistance than when doing the exercises slowly with heavy resistance.

• Resistance through the midrange (45° to 90°) tends to exacerbate patellofemoral pain because of the compressive forces on the patella. Apply resistance in arcs of motion that are pain-free on either side of the symptomatic range. This could be done using manual or mechanical resistance in the pain-free ranges.

• Strengthen both hip and ankle musculature using open-and closed-chain exercises in order to balance forces throughout the lower extremities and progress the patient toward functional independence. (See Chapters 20 and 22 for hip and ankle exercises.)

Muscular endurance training. Increase repetitions at each resistance level before increasing resistance.

Functional training. Climbing steps, sitting down and rising up from chairs and commodes, and using safe body mechanics to lift objects from the floor are often compromised in individuals with knee arthritis. It is imperative to strengthen the knee musculature using modifications of functional activities, progressing the difficulty as strength improves.

• Step-up and step-down exercises (forward, backward, lateral). Begin with a low step height, and progress to the step height the patient requires for home and community mobility. Progress to functional activities, such as climbing stairs or ladders, depending on the desired outcomes.

• Wall slides and minisquats to 90°, if tolerated. Stay within a range that does not exacerbate symptoms or cause crepitation. Practice sitting down and sit-to-stand with arm assistance to and from various chair heights. Determine if chair adaptation is needed for safe function. Correct lower extremity alignment and posterior weight shift are imperative to activate and strengthen the gluteus maximus for total lower extremity control.

• Partial lunges. This activity is progressed to include lunging to pick up small objects from the floor. Lunges are an effective way to teach body mechanics for an individual with unilateral knee impairment. Concentrate on trunk control during the motion. Have the patient activate the lumbopelvic musculature to stabilize the pelvis during the lunge activity.

• Balance activities. Balance activities are initiated at the level the patient can control. Detailed suggestions are outlined in Chapters 8 and 23.

• Ambulation. Decrease use of assistive devices as quadriceps strength improves to a manual muscle test level of 4/5 and as gait is normalized and symmetrical. Practice walking on a variety of terrains and up and down ramps, and reverse directions, first with assistance and then independently.

Improve Cardiopulmonary Endurance

Select and adapt activities to minimize irritating stresses on the knee.

• Swimming, water aerobics, and aquatic exercises provide an environment for improving muscular and cardiopulmonary function with minimal joint trauma.

• Bicycling is a low-impact form of exercise. Adjust the seat height so the knee goes into complete extension (but not hyperextension) when the pedal is down. On a stationary bike, use low resistance.

• High impact activities—with caution. For some patients, progression to running or jumping rope and other high-impact, faster-paced, or more intense activities can be undertaken so long as the joint remains asymptomatic. If joint deformity is present and proper biomechanics cannot be restored, the patient probably cannot progress to these activities.

Joint Surgery and Postoperative Management

A range of surgical options for management of arthritis of the knee is available when joint pain and synovitis cannot be controlled with conservative therapy and appropriate medical management or when destruction of articular surfaces, deformity, or restriction of motion have progressed to the point that functional abilities are significantly impaired.

The surgical procedure selected depends on the patient's signs and symptoms, activity level and age, type of disease, severity of articular damage or joint deformity, and involvement of other joints. Arthroscopic débridement and lavage are used to remove loose bodies that may be causing swelling and intermittent locking of the knee.^17,251 A number of procedures to repair damaged articular cartilage have been developed. Abrasion arthroplasty, a procedure designed to smooth worn articular surfaces and stimulate growth of replacement cartilage has met with only limited success.^17,251 More recently developed procedures used to repair small, localized articular cartilage defects of the knee, such as microfracture,^92,253 osteochondral autograft transplantation (mosaicplasty),^12,103,137 and autologous chondrocyte implantation,^45,93,298 appear to hold promise.

Synovectomy was the procedure of choice in the past for a young patient with unremitting joint effusion, synovial proliferation, and/or pain as the result of RA or juvenile RA (JRA) but with minimal destruction of articular surfaces.^35,218,251 However, it is now used infrequently. Osteotomy of the distal femur or proximal tibia (an extraarticular procedure) redistributes weight-bearing forces between the tibia and femur in an attempt to reduce joint pain during weight-bearing activities and delay the need for arthroplasty of the knee.^17,35,251 In the past, high tibial osteotomy was considered a surgical option for the active patient younger than age 50 to 55 years without active systemic disease and significant limitation of motion or joint deformity. However, because arthroplasty is now performed in younger patients than was the case a decade or two ago, osteotomy is an infrequently selected surgical option.³⁹

When erosion of articular surfaces becomes severe and pain is unremitting, total knee arthroplasty (total knee replacement) is the surgical procedure of choice to reduce pain, correct deformity, and improve functional movement.^119,160,249 Only in highly selective situations is arthrodesis (fusion) of the knee used as a salvage procedure to provide a patient with a stable and pain-free knee.

Regardless of the type of surgery selected, the goals of surgery and postoperative management are to: (1) reduce pain; (2) correct deformity or instability; and (3) restore lower extremity function. Carefully progressed postoperative rehabilitation is essential for optimal functional outcomes.

Repair of Articular Cartilage Defects

Injuries of the ligaments or menisci of the knee and acute or chronic patellofemoral dysfunction often are associated with damage to an articular surface of the knee. Surgical management of chondral defects has proved challenging because of the limited capacity of articular cartilage to heal.^45,144 However, several surgical procedures introduced during the 1990s are available for repairing small lesions in the symptomatic knee when nonoperative management or arthroscopic débridement and lavage have been unsuccessful.

Procedures include microfracture,^{92,144,253,275} osteochondral autograft transplantation/mosaicplasty,^{12,18,103,137} and autologous chondrocyte implantation.^93,144,298 These procedures are designed to stimulate growth of hyaline cartilage for repair of focal defects of articular cartilage and for preventing progressive deterioration of joint cartilage leading to osteoarthritis.^45,144

Descriptions of procedures specific to the knee are presented in this section. Regardless of the cartilage procedure selected, each requires the patient's ability and willingness to adhere to a lengthy rehabilitation process.

Indications for Surgery

The primary indication for repair of an articular cartilage defect is a symptomatic knee caused by a small to relatively large focal lesion of the tibiofemoral or patellofemoral joint. Sites typically involved are the weight-bearing portions of the medial or lateral femoral condyles, the trochlear groove, and the articulating facets of the patella.

Selection criteria when choosing the procedure include the size of the chondral lesion (in general, defects greater than 1 to 2 cm² but no more than 4 cm² are considered suitable for repair), the depth of the lesion, the location of the lesion, the elapsed time since the occurrence of the defect, and the patient's age and intended activity level. Most patients who undergo articular cartilage repair are young and active.^45,144

Procedures

Microfracture. Microfracture is indicated for repair of very small defects, usually of the medial or lateral femoral condyle or the posterior aspect of the patella. The procedure is performed arthroscopically and involves the use of a nonmotorized awl to systematically penetrate the subchondral bone and expose the bone marrow. The procedure is designed to stimulate a marrow-based repair response leading to local ingrowth of cartilaginous repair tissue (fibrocartilage) to repair the lesion.^{45,92,144,253,275}

Osteochondral autograft transplantation/mosaicplasty. For focal lesions involving chondral or subchondral tissue of the weight-bearing surfaces of the knee, osteochondral graft transplantation may be selected. It is an arthroscopic or mini open procedure involving transplantation of intact articular cartilage along with some underlying bone, resulting in a bone-to-bone graft.^{12,18,103,137} Rather than using a single piece of tissue and creating a similar size osteochondral defect at the donor site, mosaicplasty is used in which multiple, small-diameter osteochondral plugs are harvested and press-fit into the chondral defect.^{12,18,103,137}

Donor sites typically are nonweight-bearing, nonarticulating portions of the supracondylar ridge of the lateral femoral articulating surfaces or elsewhere in the knee.¹²

Autologous chondrocyte implantation. This procedure, also referred to as chondrocyte transplantation, is used for full-thickness chondral and osteochondral defects (2 to 4 cm²) of the femoral condyles or patella.^45,93,298 The procedure occurs in two stages. First, healthy articular cartilage is harvested arthroscopically from the patient. Then chondrocytes are extracted from the articular cartilage, cultured for several weeks, and processed in a laboratory to increase the volume of healthy tissue. The second phase is the implantation phase, which currently requires an arthrotomy (open procedure). After the chondral defect sites have been débrided, they are covered with a periosteal patch, typically harvested from the proximal medial tibia and secured with fibrin glue. Then millions of autologous chondrocytes are injected under the patch and into the articular defect.

Patient positioning during the first 4 hours after surgery is critical. Patients are positioned so the effect of gravity distributes the chondrocytes evenly along the base of the defect.²³² For example, after a patellofemoral repair, the patient is placed in the prone position.

Maturation of the implanted chondrocytes is a lengthy process. It may take as long 6 months for the graft site to become firm and as long as 9 months for the graft to become as durable as the healthy tissue surrounding the graft.⁹³

Osteochondral allograft transplantation. For defects larger than 4 cm², the only option for repair—although used infrequently—is an osteochondral allograft of intact articular cartilage from a cadaveric donor. However, only fresh, intact grafts, which are in limited supply and can be stored only a few days, can be used. A frozen allograft cannot be used because freezing the graft material kills the articular chondrocytes, leading to graft failure.^45,144

Other procedures. If coexisting ligament or meniscus pathology or tibiofemoral or patellofemoral malalignment are identified prior to or concomitant with surgical repair, reconstruction or realignment must be carried out for the articular cartilage repair to be successful. The most common procedures are ACL reconstruction and meniscus repair for tibiofemoral articular defects and lateral retinacular release for patellar defects.^12,93

Postoperative Management

A cautiously progressed and closely monitored rehabilitation program after articular cartilage repair procedures is critical for a successful outcome. The components and progression of a rehabilitation program, including exercise, ambulation, and functional activities, must be graded to protect the repair or graft and prevent further articular damage while applying controlled stresses to stimulate the healing process.

The progression of postoperative exercises and functional activities after microfracture, osteochondral autologous transplantation, and autologous chondrocyte implantation has many common elements, yet they vary to some degree. Detailed postoperative protocols, as well as comprehensive clinical practice guideline for each of these procedures, have been published in the literature.^{12,93,137,148,232} In addition to the type of repair employed, the rehabilitation progression is based on the size, depth, and location of the articular defect, the need for concomitant surgical procedures, and patient-related factors such as age, body mass index, health history, and preoperative activity level.

The goals during rehabilitation after articular cartilage repair are similar to those found for most knee rehabilitation programs presented in this chapter. Protected weight bearing over an extended period of time and early motion are essential after articular cartilage repair to promote maturation and maintain the health of the repaired or implanted cartilage. Special considerations for exercise and weight bearing associated with the various articular cartilage procedures are summarized in Box 21.2.^{12,93,137,148,232,298}

Total Knee Arthroplasty

Total knee arthroplasty (TKA), also called total knee replacement, is a widely performed procedure for advanced arthritis of the knee primarily in older patients (≥70 years of age) with osteoarthritis. However, during the decade between 1990 and 2000, the proportion of younger patients undergoing TKA increased significantly. During this period the proportion of knee replacements performed in the 40- to 49-year-old age group increased by 95.2% and in the 50- to 59-year-old age group by 53.7%. This indicates the criteria for TKA, traditionally reserved for the patient older than 65 years of age, have broadened.¹²²

The primary goals of TKA are to relieve pain and improve a patient's physical function and quality of life.^184,249

Indications for Surgery

The following are common indications for TKA.^119,160,249

• Severe joint pain with weight bearing or motion that compromises functional abilities

• Extensive destruction of articular cartilage of the knee secondary to advanced arthritis

• Marked deformity of the knee such as genu varum or valgum

• Gross instability or limitation of motion

• Failure of nonoperative management or a previous surgical procedure

Procedure

Background

Prosthetic replacement of one or more surfaces of the knee joint began to develop during the 1960s. To address problems with early designs, semiconstrained, two-component designs evolved. For the patient with severe anterior knee pain resulting from advanced patellofemoral deterioration, a three-component, total condylar design that included resurfacing the patellofemoral joint was developed. For advanced arthritis of just the medial or lateral aspect of the knee, the unicompartmental (unicondylar) knee arthroplasty (UKA) was developed as an alternative to TKA.^{192,212,243,284}

A therapist's knowledge of the different types of TKA and UKA used today enhances communication between the therapist and surgeon and provides a foundation for decisions made during rehabilitation.

Types of knee arthroplasty. Contemporary knee replacement procedures can be divided into several categories based on component design, surgical approach, and type of fixation (Box 21.3).^{120,160,189,192,249,284} One category is based on the number of components implanted or articulating surfaces replaced. Another is based on the degree of constraint (i.e., the amount of inherent congruency/stability in the design). Most TKA procedures today involve a two-component (bicompartmental), semiconstrained prosthetic system to replace the proximal tibia and distal femur (Fig. 21.8). These systems typically are composed of a modular or nonmodular femoral component with a metal articulating surface and a single all-polyethylene or metal-backed modular or nonmodular tibial component with a polyethylene articulating surface.^120,160,249

Occasionally, a tricompartmental design, which also resurfaces the posterior aspect of the patella with a polyethylene component, is selected if the patellofemoral joint is symptomatic.^119,160,249 For the younger patient (< 55 years of age) with advanced disease of only the medial or lateral aspect of the knee joint, a unicompartmental design often is selected to replace just one tibial and one femoral condyle.^{192,212,243,249,284}

Intact medial and lateral collateral ligaments are necessary prerequisites for semiconstrained and unconstrained TKA.^119,160,249 Fully constrained designs, now used infrequently, are reserved for the low-demand patient who has marked instability of the knee, extensive bone loss, or severe deformity or who has had previous TKA revisions.^119,160 Contemporary fully constrained designs are not hinged but have inherent medial-lateral (ML) and anterior-posterior (AP) stability and some degree of rotation of the tibia on the femur to lessen the problem of progressive loosening of the prosthetic components over time.^119,160

TKA designs also are classified as mobile-bearing or fixed-bearing. The most recent development in the evolution of TKA is the introduction of the mobile-bearing, bicompartmental prosthetic knee. A mobile-bearing knee has a rotating platform inserted between the femoral and tibial components whose top surface is congruent with the femoral implant (round-on-round articulation) but whose undersurface is flat for rotation and sliding of the tibial component (flat-on-flat articulation).^38,189,249 A fixed-bearing knee does not have such an insert.^60,249 The purpose of the mobile-bearing insert is to decrease long-term wear of the polyethylene tibial component. A mobile-bearing knee design is recommended most often for the active patient, younger than 55 to 65 years of age.²⁴⁹

Another way to classify TKA design is based on the status of the posterior cruciate ligament (PCL). Designs are described as cruciate-retaining or cruciate-excising/substituting.^{119,160,208,211,249} Although the ACL is routinely excised during knee replacement—except with UKA—the PCL can be preserved or sacrificed. If the PCL is intact to provide posterior stability to the knee, one of several cruciate-retaining designs that require less congruency and allow some degree of AP glide can be used. If the PCL is irreparably deficient, a cruciate-excising/substituting prosthesis is selected. This type of design has inherent posterior stability from the congruency of the components, a posterior prominence in the tibial component, or a cam-post mechanism built into the design. Cruciate-retaining and cruciate-excising designs can have a fixed-bearing or mobile-bearing design.²⁴⁹

Surgical approach. TKA and UKA procedures are also described in terms of the surgical approach employed.^{26,41,192,249} Since the inception of knee arthroplasty, an open approach requiring a relatively long anterior incision traditionally has been employed to provide sufficient exposure of the knee joint during the procedure. A recent advance is the development of minimally invasive knee arthroplasty.^26,192 As with traditional joint arthroplasty, minimally invasive arthroplasty is an open procedure. However, minimally invasive TKA involves a smaller incision and less soft tissue disruption to reduce postoperative pain and increase the rate of postoperative recovery. Standard (traditional) and minimally invasive surgical approaches are described later in this section.

Fixation. The method of fixation—cemented, uncemented, or "hybrid"—is another way to classify TKA procedures—that is, implants are held in place with acrylic cement, bone ingrowth (uncemented), or a combination of these two methods.^{160,210,231,297} Initially, almost all total knee replacements relied on cemented fixation. In fact, cemented fixation revolutionized knee arthroplasty.^119,231 However, a long-term complication associated with early designs of cemented prostheses was biomechanical loosening, primarily of the tibial component at the bone-cement interface. Young, active patients were believed to be at highest risk for component loosening.²⁹⁷

To address the problem of loosening, cementless (biological) fixation relying on rapid growth of bone into the surfaces of a porous-coated or beaded prosthesis was introduced and recommended primarily for the young, active patient.^{119,160,210,249,297} In addition, the use of a hydroxyapatite coating on the prosthesis has been advocated to enhance the ingrowth of bone.²⁵¹ However, long-term follow-up demonstrated that although the femoral component reliably achieved fixation to bone tibial component, loosening occurred at an even higher rate with all-cementless fixation compared with cemented fixation.^210,297 This finding gave rise to the "hybrid" TKA, which combines cemented fixation of the tibial component and cementless fixation of the femoral component.

Currently, all-cemented fixation is used most often and all-cementless used least often. A surgeon's decision whether to employ hybrid fixation is based on the patient's age, bone quality, and expected activity level and the tightness of fit of the femoral component achieved during surgery.²⁴⁹ Design modifications to augment fixation of the tibial component (e.g., with pegs or screws) continue, although the long-term value of these design changes has yet to be determined.^119,311

In summary, research continues on the biomechanics of knee arthroplasty, modifications of designs, development of better methods of fixation and new materials with better wear qualities, as well as improved surgical techniques and use of sophisticated instrumentation for alignment and placement of prosthetic components. Ongoing developments in all of these areas will continue to contribute to the success of current-day and improvement of future TKA procedures.^249,311

Operative Overview

One of several variations of standard or minimally invasive approaches with an incision along the midline or anteromedial aspect of the knee can be used. Key features of these two types of approaches are compared in Table 21.2.^{26,41,192,249} A quadriceps-splitting or a quadriceps-sparing approach is used to reach the capsule for an arthrotomy. The knee is flexed; and osteophytes, menisci, and the ACL are resected. If a posterior cruciate-substituting prosthesis is to be implanted, the PCL is also excised.

A series of surgical techniques are performed prior to inserting the implants.^120,249 Contemporary TKA employs computer-assisted, image-guided surgery to ensure precise placement and alignment of the components. Small portions of the distal femur and proximal tibia are removed and prepared for the implants. If a patellar implant is indicated, the patellar surface also is prepared and the prosthesis inserted. After trial components are inserted, soft tissue tension, collateral ligament balance, ROM, and patellar tracking are assessed. The lateral retinaculum may be released to improve patellar tracking.^138,249 Permanent components are inserted, and the capsule and other soft tissues are repaired. The area is thoroughly irrigated, and the wound is closed with the knee positioned in extension and a small suction drain in place. A sterile dressing is placed over the incision, and the area is covered from foot to thigh with a compression wrap.

Complications

Overall, the incidence of complications after TKA is low. Intraoperative complications during knee arthroplasty, such as an intercondylar fracture or damage to a peripheral nerve (e.g., the peroneal nerve), are uncommon. Because minimally invasive TKA is considered more technically challenging than conventional TKA, early reports suggest that the rate of intraoperative complications, such as fracture or malpositioning of an implant, is higher with a minimally invasive than a standard approach.²⁶ An increased incidence of intraoperative technical errors, which can affect outcomes, is associated with patient obesity.¹²⁴

Early and late postoperative complications include infection, joint instability, polyethylene wear, and component loosening. As with arthroplasty of other joints, there is a risk of wound-healing problems and deep vein thrombosis (DVT) during the first few months after surgery. Although the incidence of deep periprosthetic infection is low, it is the most common reason for early failure and the need for revision arthroplasty. In contrast, polyethylene wear of the patellar and tibial components is the most common late complication requiring revision.^52,191 The incidence of biomechanical loosening has been reduced significantly with the newer prosthetic designs and improved surgical techniques.^191,250 If mechanical loosening develops over time, it occurs most often at the tibial component and more often with cementless or hybrid TKAs than fully cemented replacements.²¹⁰

Other postoperative complications that can compromise a patient's functional recovery include limited knee flexion, joint instability leading to subluxation,^52,249 and patellar instability or tracking problems leading to impaired function of the extensor mechanism (most often an extensor lag).^138,249 Additionally, obesity has been shown to limit outcomes in a patient's mobility after TKA compared to nonobese patients.¹²⁴

Postoperative Management

Goals and interventions during progressive phases of postoperative rehabilitation after TKA are summarized in Table 21.3. Guidelines are similar for management after UKA. Interventions also may include preoperative patient education on an individual or group basis.²⁵¹ Following surgery, patients routinely receive gait training and exercise instruction while hospitalized and in a subacute rehabilitation facility. Many patients also receive home-based or outpatient therapy after discharge from inpatient care.

A patient is advanced from one phase of rehabilitation to the next based on an evaluation of their signs and symptoms and responses to selected interventions rather than solely at designated time periods. Accordingly, the timelines noted in Table 21.3 and described in the following sections are intended to serve only as general guidelines.

NOTE: The postoperative guidelines in Table 21.3 and the following sections reflect recommendations for patients who have undergone primary TKA in which a standard surgical approach was used. The suggested timelines for the progression of exercises and weight bearing tend to be more rapid after UKA than TKA and minimally invasive compared with traditional arthroplasty but slower after complex revision arthroplasty versus primary arthroplasty.

Immobilization and Early Motion

Typically, after primary TKA, the knee is immobilized in a bulky compression dressing for a day, or sometimes continuous passive motion (CPM) is initiated in the recovery room or within a day after surgery. After complicated revision arthroplasty, an extended period of immobilization may be required. The position of immobilization after primary TKA is usually extension.²⁴⁹ Although uncommon, an alternative approach is to immobilize the knee in a 90° flexion splint immediately after surgery and for brief intervals during the next day or two to achieve knee flexion as soon as possible while maintaining knee extension with exercises.¹¹²

During the initial postoperative period, it may be advisable to have a patient wear a posterior extension splint during ambulation until quadriceps control is reestablished. An extension splint also is indicated at night for a patient who is having difficulty achieving full knee extension after surgery or who had a significant preoperative knee flexion contracture.^39,249

In the past, CPM was used routinely during a patient's hospital stay after TKA.⁹⁵ At that time, a number of studies describing the benefits of CPM, such as decreased need for postoperative pain medication, decreased incidence of deep vein thrombosis, and increased or more rapid recovery of ROM, were reported in the literature.^126,151,171 However, in some of the investigations that reported greater ROM with CPM, the knees of patients in the control groups, who did not undergo CPM, were immobilized for several days to a week after surgery.^126,171

Customary practice for the past two decades has been to initiate early postoperative exercise except in some instances of complex revision arthroplasty.⁶⁶

Weight-Bearing Considerations

The extent to which weight bearing is allowable after primary TKA depends on the type of prosthesis implanted, the type of fixation used, the patient's age, size, and bone quality, and whether a knee immobilizer is worn during ambulation or transfers. With cemented fixation, weight bearing typically is permitted as tolerated immediately after surgery using crutches or a walker. During the first few days after surgery, use of a knee immobilizer may be required. The patient progresses to full weight bearing over a 6-week period.²³¹

With biological/cementless fixation, recommendations for weight bearing vary from permitting only touch-down weight bearing for 4 to 8 weeks while using crutches or a walker²¹⁰ to weight bearing as tolerated within a few days after surgery while using crutches or a walker.^39,249,251

Cane use is indicated during progression from partial to full weight bearing. Ambulation without an assistive device, particularly during outdoor walking, is not advisable until the patient has attained full or nearly full, active knee extension and adequate strength of the quadriceps and hip musculature to control the operated lower extremity.^{39,160,210,251}

Exercise Progression

Goals and exercises for progressive phases of postoperative rehabilitation after current-day TKA, noted in Table 21.3, are discussed in the following sections.^{10,39,66,175,180,225,251,312} Precautions for exercise during rehabilitation are summarized in Box 21.4.

Many of the exercises described for the early phase of rehabilitation were reported in a consensus document developed by physical therapists on the management of patients during the period of hospitalization after TKA.⁶⁶ Prior to discharge from inpatient rehabilitation, a home exercise program serves as the foundation for the remainder of the rehabilitation process, with some patients also undergoing home-based or outpatient rehabilitation for a limited number of visits.

Exercise: Maximum Protection Phase

The focus of management during the first phase of rehabilitation and the acute/inflammatory and early subacute stage of tissue healing, which extends for about 4 weeks, is to control pain and swelling (with cold and compression), achieve independent ambulation and transfers while using a walker or crutches, prevent early postoperative medical complications, such as pneumonia and deep vein thrombosis, and minimize the adverse effects of postoperative immobilization. The goal is to attain 90° of knee flexion and full knee extension by the end of this first phase of rehabilitation. However, full knee extension may not be possible until joint swelling has subsided.

It is well established that pain and joint swelling limit the function of the quadriceps muscle. In addition, there is a high correlation between quadriceps muscle weakness and impaired functional abilities during the initial period of recovery after TKA.¹⁸² Regaining quadriceps muscle strength, particularly in terminal extension, as early as possible after TKA is essential for functional control of the knee during ambulation and negotiating stairs. In addition to early postoperative exercise, neuromuscular electrical stimulation or biofeedback may be recommended as it has been shown to be safe when initiated as early as 2 days following surgery.^8,180

Goals and interventions. The following goals and exercise interventions are included in the initial phase of rehabilitation after TKA.^{10,39,66,175,180,251,312}

• Prevent vascular and pulmonary complications.

  • Ankle pumping exercises with the leg elevated immediately after surgery to prevent venous stasis and reduce the risk of a DVT or pulmonary embolism

  • Deep breathing exercises

• Control pain and swelling.

  • Cold, compression, and elevation

• Minimize reflex inhibition or loss of strength of knee and hip musculature.

  • Muscle-setting exercises of the quadriceps (preferably coupled with neuromuscular electrical stimulation), hamstrings, and hip extensors and abductors

  • Active-assisted and active straight leg raise (SLR) exercises in supine and prone positions the first day or two after surgery, postponing SLRs in side-lying positions for as long as 2 weeks after cemented TKA and for as long as 4 to 6 weeks after cementless/hybrid replacement to avoid varus or valgus stresses to the operated knee

  • Active-assisted ROM (A-AROM) progressing to active ROM (AROM) of the knee while seated and standing for antigravity knee extension and flexion, respectively.

  • As weight bearing on the operated lower extremity permits, terminal knee extension in standing, wall slides in a standing position, minisquats, and partial lunges to develop control of the knee extensors and reduce the risk of an extensor lag

• Maintain or improve strength of the contralateral lower extremity.

  • PRE of nonoperated lower extremity, particularly the quadriceps and hip extensors and abductors³¹²

• Regain knee ROM.

  • Heel-slides in a supine position or while seated with the foot on the floor to increase knee flexion

  • Neuromuscular facilitation and inhibition technique, such as the agonist-contraction technique (described in Chapter 4), to decrease muscle guarding, particularly in the quadriceps, and increase knee flexion

  • Gravity-assisted knee flexion by having the patient sit and dangle the lower leg over the side of a bed

  • Gravity-assisted or self-assisted knee extension in the supine or long-sitting position by periodically placing a rolled towel under the heel and leaving the knee unsupported or in a seated position with the heel on the floor and pressing downward just above the knee with both hands

  • Gentle inferior and superior patellar gliding techniques to prevent restricted mobility

PRECAUTION: Avoid placing a pillow under the knee while lying supine or while seated with the operated leg elevated to reduce the risk of developing a knee flexion contracture.

• Improve trunk stability and balance.

  • Trunk stabilization exercises

  • Balance activities in sitting and weight shifting in bilateral stance while adhering to weight-bearing restrictions

• Reestablish functional mobility.

  • Gait training adhering to weight-bearing restrictions with use of appropriate assistive device

  • Functional training (bed mobility, sit-to stand transfers, basic ADL)

  Criteria to progress. The criteria to progress to the intermediate phase of rehabilitation include the following.

• Minimal swelling and pain

• Well-healed incision with no signs of infection

• Independent basic ADL and ambulation with appropriate assistive device

• AROM approaching full or nearly full, active knee extension and 90° knee flexion

Exercise: Moderate Protection/Controlled Motion Phase

The emphasis of the intermediate phase of rehabilitation, which begins at about 4 weeks and extends to 8 to 12 weeks postoperatively, is to achieve approximately 110° knee flexion and active knee extension to 0° and gradually to regain lower extremity strength and muscular endurance, balance, cardiopulmonary endurance, and additional functional mobility.

By 4 to 6 weeks postoperatively, if nearly full knee extension has been achieved and the strength of the quadriceps is sufficient, most patients transition to using a cane during ambulation activities. This makes it possible to focus on normalizing the patient's gait, sit-to-stand, and stair ascent and descent patterns and improving the speed and duration of walking. In general, most improvements in a patient's functional abilities and quality of life tends to occur by 3 months postoperatively.¹²⁷

Goals and interventions. The goals and exercise interventions for the intermediate phase of rehabilitation are the following.^{10,39,66,175,182,225,251,312}

• Increase strength and endurance of knee and hip musculature.

  • Multiple-angle isometrics and low-intensity dynamic resistance exercises of the quadriceps, hamstrings, and hip musculature (extensors, abductors, external rotators) against a light grade of elastic resistance or a cuff weight around the ankle

  • Resisted SLRs in various positions to increase the strength of hip and knee musculature

  • As weight bearing allows, continue or begin closed-chain exercises including resisted terminal knee extension in standing, standing wall slides, minisquats, partial lunges, and the sit-to-stand task emphasizing proper lower extremity alignment. Include scooting forward and backward on a wheeled stool to improve functional control of the knee.

  • Add forward and backward, progressing to lateral step-ups and step-downs (initially using a low step and increasing the height of the step). Reinforce proper lower extremity alignment. To progress, perform step-ups against elastic resistance.

  • Stationary cycling with the seat positioned as high as possible to emphasize knee extension

  • Include strengthening exercises for the nonoperated lower extremity

• Continue to increase knee ROM.

  • Low-intensity self-stretching using a prolonged stretch or hold-relax technique to increase knee flexion and extension if limitation persists. Flexibility of the hip flexors, hamstrings, and calf muscles also may need to be increased for standing and ambulation activities.

  • Stationary cycling with seat lowered to increase knee flexion

  • Grade III inferior or superior patellar mobilization techniques to increase knee flexion or extension, respectively, if insufficient patellar mobility is restricting ROM

• Improve standing balance and trunk stability.

  • Trunk stabilization exercises

  • Proprioceptive and balance training progressing from bilateral to unilateral stance on stable surface, then to balance activities on an unstable surface

  • Functional reaching activities while standing or stooping

  • Tandem walking, grapevine walking initially in parallel bars for safety (See Chapter 23 for additional activities.)

PRECAUTION: A progression of balance activities for patients with TKA is typically safe to begin about 8 weeks postoperatively but must be based on the ability to control the knee during stance, weight-bearing restrictions, and the absence of pain.²²⁵

• Continue to improve functional mobility.

  • Symmetrical heel-toe walking, ambulation on a variety of surfaces and inclines, kneeling and getting up to a standing position, and ascending and descending stairs

  • Functional exercises: backward walking, side-stepping, marching, stepping over small objects

• Improve cardiopulmonary endurance.

  • Aerobic conditioning on a stationary cycle or upper body ergometer, emphasizing increased duration

Criteria to progress. The following criteria typically must be met to progress to the final phase of rehabilitation following TKA.

• AROM: full knee extension (no extensor lag), 110° knee flexion

• Quadriceps/hamstring and hip muscle strength: at least 70% (or 4/5 muscle testing grade) compared to uninvolved leg

• Minimal to no pain during exercises and ambulation with or without a cane

Exercise: Minimum Protection/Return to Function Phase

Beginning at approximately 8 to 12 weeks and beyond after surgery, the emphasis of the final phase of rehabilitation is on task-specific strengthening exercises, proprioceptive and balance training, advanced functional training (see Chapter 23), and continued cardiopulmonary conditioning so that the patient develops the strength, power, balance, and endurance needed to return to a full level of functional activities in the community. (Refer to Table 21.3 for a summary of goals and interventions during the final phase of rehabilitation.)

Despite persistent strength and power deficits, altered movement patterns and insufficient speed and endurance during functional activities, patients often are discharged from supervised therapy 2 to 3 months postoperatively after attaining functional ROM of the knee and the ability to ambulate independently with an assistive device. However, deficits in physical function have been shown to persist for an average of 10 months²⁹¹ to a year or more after surgery.¹⁸²

It is likely that some patients, especially those living in the community, could benefit from an intensive exercise program during the late phases of rehabilitation to perform demanding physical activities more efficiently, such as ascending and descending stairs and returning to selected recreational activities.

With the trend toward an increasing number of young (< 60 years of age) and active patients undergoing TKA,¹²² patient education is essential to help patients understand the detrimental effects of repetitive, high-impact activities (work-related, fitness-related, recreational) on the prosthetic implants and to learn how to select activities that promote fitness but are least likely to reduce the longevity of the prosthetic knee.^106,139,169 Accordingly, patients are advised to participate in low-impact physical activities after TKA to reduce the risk of component wear and mechanical loosening over time and the premature need for revision arthroplasty.

For the patient who wishes to participate in athletic activities after TKA, there are a number of considerations. Factors that influence participation include the level of demand (intensity and load) of an athletic activity, a patient's body weight, overall level of fitness, and preoperative experience with the activity and the technical quality of the knee replacement and related soft tissue balancing or reconstruction.^106,139

Physical activities for fitness and recreation that are highly recommended, recommended with caution, or not recommended after TKA are noted in Box 21.5.^106,139,169

Patellofemoral Dysfunction: Nonoperative Management

Related Patellofemoral Pathologies

Historically, the differential diagnosis of patellofemoral (PF) pathologies has been plagued with confusion, largely related to the use of broadly inclusive terminology such as chondromalacia patellae and patellofemoral pain syndrome (PFPS). In an attempt to more clearly identify the anatomical structures involved and the biomechanical changes leading to dysfunction, several classification systems have been proposed. These classifications include guidelines for intervention based on impairments and activity limitations.^115,302

PF Instability

Instability includes subluxation or dislocation of a single or recurrent episode. There may be an abnormal Q-angle, dysplastic trochlea (shallow groove or flat lateral femoral condyle), patella alta, tight lateral retinaculum, and inadequate medial stabilizers (vastus medialis oblique muscle [VMO] and medial patellofemoral ligament [MPFL]). There may be associated fractures. Usually the instability is in a lateral direction. The dislocation may derive from direct trauma to the patella or from a forceful quadriceps contraction while the foot is planted and the femur is externally rotating while the knee is flexed. Recurrent dislocation is usually an indication for surgery to redirect the forces through the patella.

PF Pain with Malalignment or Biomechanical Dysfunction

Patellofemoral pain reportedly due to malalignment or biomechanical dysfunction includes impairments that cause an increased functional Q-angle such as femoral anteversion, external tibial torsion, genu valgum, or foot hyperpronation. There may be a tight lateral retinaculum, weak VMO muscle, neuromuscular deficits in the hip musculature, incompetent MPFL, patella alta, patella baja, generalized laxity, or dysplastic femoral trochlea. There is usually abnormal patellar tracking, and there may be discordant firing of the quadriceps muscle.¹¹⁵

PF Pain Without Malalignment

Patellofemoral pain without malalignment includes many subcategories of lesions that cause anterior knee pain.

Soft tissue lesions. Soft tissue lesions include plica syndrome, fat pad syndrome, tendonitis, IT band friction syndrome, and bursitis.

• Plica syndrome describes a condition related to irritation of remnants of embryological synovial tissue around the patella. With chronic irritation, the tissue becomes an inelastic, fibrotic band that is tender during palpation. When acute, the tissue is painful during palpation. The band is usually palpable medial to the patella, although there are variations in its location.^23,131

• Fat pad syndrome involves irritation of the infrapatellar fat pad from trauma or overuse.

• Tendonitis of the patellar or quadriceps tendons, sometimes called jumper's knee, typically occurs from overuse as the result of repetitive jumping. Tenderness occurs along the attachment of the tendon to the patella. Symptoms may be exacerbated secondary to tightness quadriceps.²⁹⁴

• IT band friction syndrome is irritation of the IT band as it passes over the lateral femoral condyle. Contributing factors could be tight tensor fasciae latae or gluteus maximus (see discussion in Chapter 20). Because the IT band attaches to the patella and lateral retinaculum, it may cause anterior knee pain.

• Prepatellar bursitis, also known as housemaid's knee, is the result of prolonged kneeling or recurrent minor trauma to the anterior knee. When inflamed, there may be restricted motion due to swelling and pain caused by direct pressure or pressure from the patellar tendon.

Tight medial and lateral retinacula or patellar pressure syndrome. There is increased contact pressure of the patella in the trochlear groove.

Osteochondritis dissecans of the patella or femoral trochlea. Osteochondral lesions result in pain on the retro surface of the patella that is worse during squatting, stooping, ambulating, and descending steps. The knee may give way or lock. There may be loose bodies within the joint.

Traumatic patellar chondromalacia. With chondromalacia, there is softening and fissuring of the cartilaginous surface of the patella, which is diagnosed with arthroscopy or arthrography.¹¹⁵ It may eventually predispose the joint to degenerative arthritis or basal degeneration of the middle and deep zones of the cartilage.⁹⁴ Causes of degeneration may include trauma, surgery, prolonged or repeated stress, or lack of normal stress such as during periods of immobilization.²⁰⁹

PF osteoarthritis. Osteoarthritis may be idiopathic or post-traumatic and is diagnosed by radiographic changes consistent with degeneration.

Apophysitis. Osgood-Schlatter disease (traction apophysitis of the tibial tuberosity) and Sinding-Larsen Johansson syndrome (traction apophysitis on the inferior pole of the patella) occur during adolescence as a result of overuse during rapid growth. They are self-limiting conditions.

Symptomatic bipartite patella. Most bipartite patellae (due to patellar ossification variants) are asymptomatic, but trauma may disrupt the chondro-osseous junction leading to symptoms.¹¹⁵

Trauma. Trauma includes tendon rupture, fracture, contusion, and articular cartilage damage that results in inflammation, swelling, limited motion, and pain with dysfunction whenever contracting the quadriceps, such as during stair climbing, squatting, and resisted knee extension.

Etiology of Symptoms

The cause of anterior knee pain may be direct trauma, overuse, faulty patellar tracking from malalignment due to anatomical variations or soft tissue length and strength imbalances in the hip, knee, or ankle/foot; degeneration; or a combination of these factors.^{33,61,166,227,228,245,260,292,294,308} An attempt should be made to determine the causative factors based on the patient's history and a comprehensive and sequential examination.

Consensus on Factors Leading to PF Symptoms

A consensus statement summarizing input from leaders and researchers studying PF pain categorized factors leading to PFPS into local, distal, and proximal influences. The following are examples of these factors.⁵⁴

Local factors. Local factors include structures around the joint itself, such as infrapatellar fat pad, ligaments, quadriceps tendon, medial and lateral retinaculum, and subchondral bone. Symptoms may be provoked by faulty mechanics. Walking and squatting increase PF joint stress.

Distal factors. Factors arising from the foot include an externally rotated foot during relaxed stance, rearfoot eversion at heel strike, delayed or prolonged rearfoot eversion during walking and running, and increased midfoot mobility.

Proximal factors. Factors arising from the hip region include altered hip kinematics of increased hip adduction and internal rotation during specific tasks such as running and single-limb activities of squatting, jumping, and drop landing. These may be associated with hip abductor and eternal rotator muscle weakness.

Common Impairments, Activity Limitations, and Participation Restrictions

Structural and functional impairments. Impairments that may be associated with PF dysfunction include the following.^{33,61,142,166,224,227,228,245,260,290,292,294,308}

• Pain in the retropatellar region

• Pain along the patellar tendon or at the subpatellar fat pads due to irritation

• Patellar crepitus; swelling or locking of the knee

• Altered lower extremity alignment (Fig. 21.9), specifically increased hip adduction and internal rotation and dynamic knee valgus (valgus collapse) that occurs during weight-bearing activities, such as ascending and descending stairs, squatting, or landing after a jump^{121,172,227,228,229,238,271}

• Weakness of the hip abductor, external rotator, and/or extensor muscles^{24,121,172,224,227-228,238,271}

• Weakness, inhibition, or altered recruitment or timing of firing of the VMO muscle⁴⁹

• Decreased flexibility of the tensor fasciae latae, hamstrings, quadriceps, or gastrocnemius and soleus muscles^224,227

• Overstretched medial retinaculum

• Restricted lateral retinaculum, IT band, or fascial structures around the patella

• Decreased medial gliding or medial tipping of the patella

• Pronated foot

Activity limitations and participation restrictions. Limitations and restrictions associated with the impairments include the following.

• Limited performance of basic ADL as the result of pain or poor knee control (valgus collapse)

• Pain-related limitations of functional mobility (e.g., reduced ability to get in or out of a chair or car, ascend and descend stairs, walk, jump, or run) that are necessary to carry out ADL and IADL, work, and community, recreational, or sport activities

• Inability to maintain prolonged flexed knee postures, such as sitting or squatting, as the result of pain and stiffness in the knee

Patellofemoral Symptoms: Management—Protection Phase

When symptoms are acute, treat them as any acute joint problem—with modalities, rest, gentle motion, and muscle-setting exercises in pain-free positions. Pain and joint effusion inhibit the quadriceps,²⁷⁹ so it is imperative to reduce irritating forces. Splinting the patella with a brace or tape may unload the joint and relieve the irritating stress.

Patellofemoral Symptoms: Management—Controlled Motion and Return to Function Phases

When signs of acute pain and inflammation are no longer present, management is directed toward correcting or modifying the biomechanical factors that may be contributing to the impairment. Because no one factor or combination of factors has been identified as the direct cause or effect of PF pain symptoms, it is imperative to develop interventions that address the scope of impairments identified during the examination.²²⁸ It is also important to integrate the concept of regional interdependence in the application of exercise interventions by addressing proximal weakness and tightness, impaired stability, and distal malalignment that may place excessive stress through the PF joint.^109,227

Management during the controlled motion and return to function phases of rehabilitation typically emphasizes increasing strength, dynamic control, and pain-free mobility of the knee and hip; modifying abnormal movement strategies that may contribute to impairments; and improving stability of the pelvis and trunk, balance, and functional abilities.

Patient Education

Instructions. Because end-range stress and prolonged postures tend to exacerbate symptoms, instruct the patient to avoid positions and activities that provoke the symptoms.

• Minimize or avoid stair climbing and descending until the hip and knee muscles are strengthened to a level at which they can control knee function without symptoms.

• Do not sit with the knees flexed excessively for prolonged periods. During sitting, periodically perform ROM of the knee to relieve stasis.

Home exercise program. Implement a home exercise program to reinforce supervised training. Prior to discharge, provide instructions for a safe progression of exercises and functional activities.

Increase Flexibility of Restricting Tissues

Identify any structures that could be contributing to faulty mechanics and establish a stretching program. The gastrocnemius, soleus, quadriceps, hamstring, and tensor fasciae latae (TFL) muscles have been identified as specific muscles with reduced flexibility in individuals with patellofemoral dysfunction.^224,227,290 Self-stretching techniques are described in the exercise section of this chapter. Techniques to stretch the two-joint muscles that cross the hip and knee are described in Chapter 20, and those that cross the knee and ankle are described in Chapter 22.

Because restrictions related to insertion of the IT band and the lateral retinaculum may contribute to decreased patellar mobility and faulty patellar tracking in some patients with PFPS, specific techniques to address these impairments are described in this section.

Patellar mobilization: medial glide. Position the patient side-lying. Stabilize the femoral condyles with one hand under the femur, and glide the patella medially with the base of the other hand (Fig. 21.10).⁹⁷ There is usually greater mobility with the knee near extension; progress by positioning the knee in greater flexion prior to performing the medial glide.

Medial tipping of the patella. Position the patient supine. Place the thenar eminence at the base of the hand over the medial aspect of the patella. Apply a posterior force to tip the patella medially. While the patella is held in this position, apply friction massage with the other hand along the lateral border (Fig. 21.11). Teach the patient to self-stretch in this manner.

Patellar taping. Although the use of patellar taping to realign the patella and provide a prolonged stretch has been recommended in early resources,^97,166 the primary benefit of taping identified in two systematic reviews of the literature^22,49 is the reduction of anterior knee pain during provoking activities. However, it is not clear whether pain relief is the result of patellar realignment from taping.

Improve Muscle Performance and Neuromuscular Control

Because many possible diagnoses fall under the category of PFPS, various biomechanical influences may be the precipitating or perpetuating cause of the symptoms. Impaired strength, endurance, and control of the knee extensors and hip musculature (extensors, external rotators, and abductors), as well as impaired stability of the trunk and pelvis, must be addressed.^227,228,229

However, not all patients with PF symptoms benefit from the same exercises. Consequently, it is imperative that the therapist design a progression of exercises that addresses the specific impairments of each patient. Exercises to improve muscle performance and functional control in associated regions proximal and distal to the knee are described in Chapters 16, 20, and 22, respectively. Additional lower extremity exercises are described in Chapter 23.

VMO Emphasis: A Closer Look

Although it is not possible to isolate contraction of the VMO, it is accepted that the line of pull of this component of the quadriceps muscle influences the tracking of the patella. Consequently, one aspect of management traditionally has been directed toward developing awareness of the VMO contraction during quadriceps muscle activation. Tactile cues over the muscle belly, electrical stimulation, or biofeedback can be implemented to reinforce the VMO contraction during knee extension exercises.

It is now well accepted that exercise programs for patients with PFPS should target regions proximal to the knee.^{85,161,195,290} However, substantial attention also has been given to the need for activating the VMO through various weight-bearing and nonweight-bearing exercises and functional activities.^6,49,61,166 As discussed in this section, however, evidence is inconsistent regarding the onset timing and activation of the VMO in individuals with and without PFPS, the role of the VMO/VL ratio, and the effectiveness of various nonweight-bearing and weight-bearing exercises and functional activities to promote VMO activation.^{49,116,130,142,165,269,292} Evidence about selected exercises is summarized in the following section, but further investigation is warranted.

Nonweight-Bearing (Open-Chain) Exercises

NOTE: There is controversy regarding compressive forces and stress on the PF joint with open-chain exercises.^67,96 The type of resistance (constant, variable, or isokinetic) places different demands on the quadriceps muscle in terms of maximum effort at various ranges. The resultant force from the quadriceps tendon and patellar tendon and the patellar contact area also vary through the ROM. Therefore, the stress on the articulating surface of the patella varies. There is little or no contact of the patella with the trochlear groove from 0° to 15° of flexion,⁶⁷ so pain felt in that range could derive from irritation of the patellar fat pads or synovial tissue. Greatest patellar stress is at 60° and compression loads at 75°, so pain may be provoked in these ranges when maximum torque from the resistance force is applied in these ranges.⁶⁷ Where the pathology is located affects where in the range the patient feels pain.⁹⁶ It is recommended that when examining the patient, the range where pain is felt be noted and resistance loads that cause pain in that range be avoided.

Quadriceps setting (quad sets) in pain-free positions. Have the patient set the quads with the knee in various positions while focusing on developing tension in the VMO. Because the site of irritation varies among patients with PF dysfunction, identify pain-free positions to ensure nondestructive loading.^67,96

Quad sets with straight-leg raise. Have the patient perform straight-leg raising (SLR) exercises in supine or long-sitting positions to target quadriceps control. Because many fibers of the VMO originate on the adductor tendons and medial intramuscular septum, it was suggested a number of years ago that simultaneous activation of the hip adductors during contraction of the quadriceps might provide a firm base for the VMO.³⁴ As a result, some exercise programs for treatment of PFPS^6,61,166 have recommended combining SLR exercises with isometric hip adduction or external rotation of the femur (so that the adductors contract during the SLR exercises). However, a study using electromyography (EMG) demonstrated that SLR exercises performed in the supine position with simultaneous external rotation of the femur or resisted isometric hip adduction were no more effective in activating the VMO relative to the VL than SLR exercises performed with the femur in neutral rotation.¹³⁰

Progression of resisted isometrics. Initiate multiple-angle isometrics against resistance to knee extension in pain-free positions as tolerated by the patient. During resisted isometrics of the knee extensors, have the patient simultaneously resist medial rotation of the tibia to optimize activation of the VMO.¹⁴²

Short-arc terminal extension. Begin with the patient supine and knee flexed around 20° (see Fig. 21.23). If tolerated and the motion is not painful, apply light resistance at the ankle. Strengthening in terminal extension trains the muscle to function where it is least efficient because of its shortened position and where there is minimal patellar compression because it is superior to the femoral groove. End-range knee extension is needed when lifting the leg into bed and moving the covers, as well as when lifting the leg into a car.

PRECAUTION: If there is irritation of the synovial lining of the suprapatellar pouch or bursa, terminal knee extension may be painful and should be avoided until the pain subsides.

Weight-Bearing (Closed-Chain) Exercises

A progression of closed-chain/axial-loading exercises, typically performed in weight-bearing positions, should be a major component of an exercise program for PFPS to reduce PF symptoms, increase muscle performance and dynamic control of knee, hip, and trunk, and to improve neuromuscular control/response time and balance.^{25,110,161,195,290} As discussed previously, if excessive valgus alignment of the knee occurs during weight-bearing activities involving knee flexion (squats, lunges, stair ascent or descent, or landing from a jump), it may be indicative of weakness of hip abductors, extensors, and/or external rotators. Strengthening these muscle groups in weight-bearing positions and practicing movement strategies in proper alignment should be a priority.^{110,161,227,228,290}

PRECAUTION: Because there are higher patellar compressive loads when the knee is flexed beyond 60° during weight bearing, exercises and activities with the knee flexed beyond this angle may provoke symptoms. Use caution when the patient is ready to progress beyond 60°. Have the patient carefully monitor symptoms and stop the exercise if symptoms develop.

• If full weight bearing is painful, begin with partial weight-bearing exercises. Progress exercises in standing as tolerated.

• To improve strength and muscular endurance, have the patient perform multiple repetitions of appropriate exercises until PF symptoms or loss of control just begins to occur. Do not push beyond that point in order to avoid faulty mechanics or loss of control.

• Initiate terminal knee extension against light resistance in standing for end-range knee control (see Fig. 21.26).

• Introduce bilateral progressing to unilateral minisquats, which may be useful for improving patellar tracking, early in the exercise program when weight bearing and partial squatting are tolerated and do not provoke symptoms (see Fig. 21.27). Be sure that the knees remain aligned over the toes during squatting.

• Progress dynamic exercises by adding double-leg, then single-leg standing wall slides, short-step, then long-step lunges, and forward, backward, and lateral step-ups and step-downs to the exercise program. Add elastic resistance for further challenge.

NOTE: Based on a study of adults without PFPS, there is some evidence to suggest that the VMO/VL ratio is higher during single-leg minisquats than a maximum voluntary isometric quadriceps contractions performed in a standing position.¹¹⁶

• Select resistance equipment for progressive strengthening and muscular endurance training that incorporates weight bearing, such as the seated leg press, the Total Gym^® unit, and the stepping machine.

• Combine balance and agility training with strengthening exercises in weight-bearing positions.

• Include plyometric training for individuals wishing to return to high-demand activities if symptoms do not recur (see Chapter 23).

Functional Activities

Practice simulated functional activities and activity-specific drills without provoking symptoms to prepare the patient to return to the desired activities (see Chapter 23). If abnormal lower extremity alignment occurs during weight-bearing activities despite improvements in muscle strength and endurance, integrate movement reeducation into activity-specific drills to reinforce proper movement strategies.

Modify Biomechanical Stresses

Assess lower extremity mechanics, and modify any faulty alignment. If the patient exhibits excessive foot pronation, a foot orthosis, such as a medial wedge, may reduce the stresses at the knee and decrease PF pain.^65,100 However, in adults without PFPS, use of a either a medial or lateral wedge or no wedge has been shown to have no significant impact on activation of the VMO and VL muscles during a single-leg minisquat and a maximum isometric contraction of the quadriceps in a standing position.¹¹⁶

Patellar Instability: Surgical and Postoperative Management

Following conservative (nonoperative) management of a primary (first-time) patellar dislocation, the rate of recurrence is between 15% to 44% and is as much as 50% after subsequent episodes.⁴⁷ When nonoperative interventions fail in the management of patellar instability, including acute and recurrent dislocation or chronic subluxation and associated pain, crepitus, or degeneration of the articular surfaces of the PF joint, surgery usually is indicated.

Surgical interventions can be used to alter the alignment of the patella, correct imbalances of the static stabilizers (see Fig. 21.4) of the patella and knee, decrease an abnormal Q-angle (see Fig. 21.3 for depiction of Q-angle measurement), improve tracking of the patella, and débride or repair articular surfaces of the PF joint. However, before a surgical procedure is selected, the etiology of symptoms and identification of factors contributing to patellar instability must be determined by a thorough physical examination and radiographic and arthroscopic evaluation.

Overview of Surgical Options

Types of surgical options for lateral patellar instability are noted in Box 21.6.^{40,46,47,86,87,88,89,114,178,179,194,216,226,233} Numerous variations of operative procedures fall under each of these categories. Some are arthroscopic procedures, whereas others involve an open approach. Often a combination of procedures is necessary.

When soft tissue abnormalities contribute to lateral patellar instability, a proximal realignment procedure, such as repair or reconstruction of the MPFL or VMO imbrication, is often selected. A distal realignment procedure that involves a tibial tubercle osteotomy with patellar tendon transfer is selected when an osseous abnormality is the underlying cause of patellar instability. Repair of chondral lesions associated with acute or recurrent patellar dislocation or trauma may also be necessary.¹⁷⁹ In contrast, TKA or patellectomy (a salvage procedure) is performed only for end-stage PF arthritis and collapse of the joint space.^87,179,216

The two broad categories of surgery for patellofemoral instability—proximal and distal realignment of the extensor mechanism—may be performed with or without a lateral retinacular release (LRR). As an independent procedure, LRR has been shown to be useful for alleviating or reducing patellofemoral pain if the cause of the pain stems from compression of lateral structures of the knee (lateral compression syndrome) as the result of an excessive lateral tilt of the patella (without subluxation) but not for management of lateral patellar instability.^{47,79,87,179,226}

Operative procedures, other than proximal or distal extensor mechanism realignment, sometimes are used for recurrent patellar instability. Trochleoplasty, which involves deepening of the trochlear sulcus, may be indicated if trochlear dysplasia is contributing to patellar instability.⁴⁷ If excessive rotational deformity of the lower extremity is determined to be an underlying cause of severe patellar malalignment and recurrent instability, a recently reported procedure—supratubercle, derotational, high tibial osteotomy—may be indicated as an alternative to proximal or distal realignment procedures.²¹⁹

After either proximal or distal extensor mechanism realignment, a number of factors influence the rate of progression of rehabilitation. They include the type of surgical procedure performed; the patient's age, general health, and severity of patellofemoral symptoms prior to surgery; the presence of other pathologies; the desired functional outcomes; and the patient's adherence to the prescribed home exercise program and motivation to return to functional activities.

Proximal Extensor Mechanism Realignment: Medial Patellofemoral Ligament Repair or Reconstruction and Related Procedures

Repair, realignment, or reconstruction of the static and dynamic medial patellar support structures, such as the MPFL, are surgical options performed with or without LRR for the patient with recurrent lateral patellar instability (dislocation or subluxation) and associated pain and compromised function despite a course of nonoperative treatment.^4,40,47,196 MPFL repair or reconstruction also may be used following an acute, first-time lateral patellar dislocation as the result of trauma. Other proximal realignment procedures include VMO imbrication (advancement) and medial retinacular reefing/tightening. These soft tissue procedures are also appropriate for the skeletally immature patient with patellar instability or may be used in conjunction with distal realignment of the extensor mechanism involving an osteotomy in the skeletally mature patient.^87,114

Indications for Surgery

Although opinion varies, the following are often cited as indications for MPFL repair or reconstruction or other proximal realignment procedures with or without LRR.^{4,40,47,87,88,114,194,196,216,226}

• Deficiency (acute tear, chronic laxity) of the medial patellar support structures, in particular the MPFL, a primary static stabilizer, leading to malalignment and recurrent instability of the patella

• Excessive (or abnormal) lateral tracking of the patella and insufficiency of the VMO, a primary dynamic medial stabilizer of the patella

• Normal boney architecture (normal tibial tubercle-trochlear groove distance) and no evidence of patella alta trochlear dysplasia

• Painful, lateral compressive forces at the patellofemoral joint and persistent lateral tilt of the patella despite a previous LRR

• An appropriate realignment option for the skeletally immature patient with patellar instability¹¹⁴

CONTRAINDICATIONS: Proximal realignment procedures are not appropriate for patients with articular degeneration of the medial patella, patella alta, or trochlear dysplasia, because they may exacerbate or have no impact on symptoms.^87,114

Procedures

Background and Operative Overview

Proximal realignment procedures use an open surgical approach through a medial parapatellar incision preceded by an arthroscopic examination of the knee, LRR, débridement of any loose osteochondral fragments or partial-thickness lesions, and, if necessary, microfracture for full-thickness chondral lesions.¹⁷⁹

MPFL repair or tightening. An acute lateral patellar dislocation usually results in disruption of the MPFL and is managed with a direct repair.^40,114 Repair is also an option if the ligament is lax as the result of recurrent dislocations. To expose the MPFL, the medial retinaculum must be opened. Depending on the location(s) of the tear, the ligament is reattached to the femoral condyle or patella or to both boney surfaces with suture anchors, or the ligament fragments are repaired with nonabsorbable locking sutures in a pants-over-vest fashion.

MPFL reconstruction. This procedure, which has many variations, is used if the MPFL is incompetent as the result of recurrent lateral dislocation or subluxation or if a previous repair or reefing of the ligament has failed. Reconstruction involves reinforcement of the MPFL with an autogenous hamstring, TFL, or quadriceps tendon graft or allograft.^4,62,196

Depending on the type of reconstruction and graft selected, the patellar and femoral ends of the graft are secured in drill holes with sutures, suture anchors, or screw fixation. In other procedures drill holes are not required, therefore eliminating the risk of patellar fracture.

VMO imbrication (advancement). This procedure is performed to improve the resting length-tension relationship of the VMO by moving the muscle to a more central and distal location.^{87,194,216,226}

Lateral retinacular release and other concomitant procedures. If a lateral patellar tilt is identified, LRR is indicated to reduce the tilt and restore the balance of the patella in the trochlea.^{46,87,226,233} LRR is performed arthroscopically through several lateral parapatellar portals. The procedure "releases" the lateral structures supporting the patellofemoral joint, specifically the superficial and deep portions of the lateral retinaculum and the lateral patellofemoral and patellotibial ligaments by means of an incision extending from the superior lateral pole of the patella to just lateral and inferior to the patellar tendon.¹⁷⁹ The location of the incision is such that the superior lateral and inferior lateral geniculate arteries are cut and must be cauterized immediately and tied. However, the release leaves the tendinous portion of the VL muscle intact so as not to compromise the function of the quadriceps. Electrocautery¹⁹⁴ and, most recently, radiofrequency ablation⁸⁹ are alternatives to surgically incising the retinaculum. The advantages of these methods for releasing the lateral structures are less bleeding and subsequent hemarthrosis.

In addition to repair or reconstruction of the MPFL, sometimes the medial patellotibial and medial patellomeniscal ligaments must be tightened or repaired.^87,88 A boney distal realignment procedure also may be combined with a medial soft tissue repair or reconstruction.^87,88,194

Complications

Postoperative complications that can occur with any of the patellofemoral surgeries include a superficial infection, but rarely an intra-articular infection, or a DVT. Patellar adhesions and arthrofibrosis can compromise postoperative ROM.

In rare instances, complex regional pain syndrome can develop (see Chapter 13).⁴⁸ There are also complications seen in proximal realignment procedures and LRR.^87,156

Following proximal realignment. Overtightening medial soft tissue structures or "overtensioning" the native MPFL or graft tissue during repair or reconstruction, inaccurate graft placement, and/or excessive imbrication of the VMO can exacerbate pain and increase loads on medial articular surfaces, leading to deterioration.^4,40,47 Significant scarring or over-tightening of medial tissues also can cause increased patellar rotation and excessive medial tracking leading to retropatellar erosion or increased risk of medial instability of the patella.^40,87 In contrast, inadequate medial tightening or VMO realignment may result in no change in patellar position, tracking, or a patient's symptoms. Although the risk of patellar fracture is low, it is a complication that can occur during MPFL reconstruction procedures that require patellar drill holes for graft placement and fixation.⁴⁷

Entrapment, irritation, or a neuroma of the saphenous nerve as it passes the adductor tubercle and splits at the pes anserine tendon can occur with any procedure involving structures on the medial side of the knee.⁸⁷

Following LRR. Several complications may occur with LRR.^22,89,156 Because of the location of the geniculate artery, hemarthrosis can occur if it is not adequately cauterized during surgery. Thermal injury to overlying skin can occur with radiofrequency ablation or electrocautery.⁸⁹ Another complication, postoperative medial patellar subluxation, can develop as the result of the lateral release extending too far proximally, causing weakness of the VL muscle. In rare instances following VMO advancement, rupture of the quadriceps tendon occurs.

Postoperative Management

Postoperative rehabilitation after MPFL repair or reconstruction or other proximal realignment procedures follows a course summarized in Table 21.4.^{4,40,88,156,196} The patient is progressed through each phase of rehabilitation based on signs and symptoms and the attainment of phase-specific goals.²⁰⁴

Immobilization and Weight-Bearing Considerations

A compression dressing is applied following surgery, and the knee is immobilized in a range-limiting, hinged orthosis locked in extension or in a posterior splint to prevent excessive knee flexion and protect the repaired or reconstructed soft tissues. Some surgeons allow removal of the immobilizer for early ROM in a protected range or while wearing the range-limiting orthosis within a few days after surgery,^4,40,156,196 whereas others advocate continuous immobilization for a week postoperatively.^114,226

During ambulation with crutches in the early postoperative period, the knee orthosis is locked in extension. From 25% weight bearing to weight bearing as tolerated is permitted on the operated extremity. Full weight bearing with the immobilizer locked is permitted by about 4 weeks after surgery.¹⁹⁶ Full weight bearing with the orthosis unlocked and without an assistive device is permitted only when the patient can control the knee and has achieved full, pain-free passive and active knee extension (no evidence of an extensor lag/quadriceps lag).^156,226

Exercise Progression

Exercise goals following MPFL repair or reconstruction or VMO imbrication are directed toward restoring and improving the function of the entire lower extremity and trunk, not just the knee.^{79,156,161,228} As with nonoperative management of patellofemoral dysfunction, many of the exercises traditionally selected for a patient's rehabilitation have focused on regaining pain-free knee ROM, maintaining patellar mobility, and recruiting the quadriceps mechanism as a unit and the VMO in particular. These interventions are designed to prevent or remediate patellar restrictions and an extensor lag.^{61,130,156,274,283}

A more recent but equally important postoperative focus for exercise interventions is remediating strength deficits in the trunk, pelvis, and hip abductor, external rotator, and extensor muscles and improving flexibility of the hip and ankle musculature.^{121,161,224,227,228}

Exercise goals, a progression of exercise interventions, and criteria to progress from one phase of rehabilitation to the next after MPFL repair or reconstruction or other proximal realignment procedures are summarized in the following sections.^88,156,196 Exercise precautions after proximal and distal extensor realignment procedures are noted in Box 21.7.^114,156,196

Exercise: Maximum Protection Phase

Goals and interventions. During the first 4 weeks after surgery, the repaired or reconstructed medial patellar tissues are in the acute and subacute stages of healing and vulnerable to excessive stresses. The goals and interventions during this period are directed toward achieving independent ambulation with crutches; controlling pain and swelling; preventing complications, such as a DVT or adhesions; and beginning to regain quadriceps control and ROM of the knee while protecting the reconstructed soft tissues (see Table 21.5).

• Achieve independent ambulation. Gait training with crutches for protected weight bearing and knee orthosis locked in extension

• Control pain and swelling. Apply cold and compression regularly throughout the day.

• Patient education. Review weight-bearing and exercise precautions with the patient to protect the repaired ligament or graft tissue while it is most vulnerable to excessive stresses (see Box 21.7). Establish and teach a home exercise program.

• Restore ROM. Perform knee flexion/extension exercises (PROM→A-AROM and AROM) in the range-limiting orthosis within a day or two after surgery. Depending on the type of repair or reconstruction performed, the goal is to attain full passive and active knee extension and at least 90° flexion by the end of week 4.^88,156,196 Stretch hip and ankle musculature, if restricted.

• Maintain patellar mobility. Apply gentle (grades I and II) patellar mobilization (superior and inferior) to reduce pain and prevent adhesions.

• Reestablish neuromuscular control and improve muscle performance. Begin gentle quadriceps setting for knee control and active superior patellar gliding with emphasis on VMO activation augmented with pain-free neuromuscular electrical muscle stimulation or biofeedback. While wearing the orthosis locked in extension, initiate SLRs in supine, prone, and side-lying positions for hip control. With the orthosis unlocked, begin partial-range heel-slides in the supine position and bilateral minisquats and heel raises when 50% pain-free weight bearing on the operated side is possible.

  Criteria to progress. Criteria to progress to the intermediate phase of rehabilitation include^156,196:

• Minimal pain and swelling.

• Incision healing well; no signs of infection.

• Full, active knee extension (no evidence of extensor lag) and at least 90° of knee flexion.

Exercise: Moderate Protection/Controlled Motion Phase

Goals and interventions. During the intermediate phase of rehabilitation (from approximately 4 to 8 weeks postoperatively), soft tissues are in the repair and remodeling stage of healing. Full weight bearing without an assistive device but with the orthosis locked typically is permitted by 4 to 6 weeks after surgery. The patient should be able to achieve functional knee ROM by the end of this phase of rehabilitation.

As symptoms subside and quadriceps strength improves, the focus of this phase of rehabilitation is to establish a normal gait pattern with the orthosis unlocked, continue to increase knee ROM, and increase flexibility of hip and ankle structures if restricted. It is equally important to develop strength and endurance of hip and trunk musculature, improve neuromuscular control/response time and balance, regain cardiopulmonary endurance, and progress and reinforce the home exercise program.

• Normalize the gait pattern. If full weight bearing is pain-free and quadriceps control is sufficient (no extensor lag), practice walking with crutches or a cane with the orthosis unlocked.

• Restore ROM and joint mobility. Begin low-intensity, prolonged stretching and grade III joint mobilization to increase ROM of restricted areas. Achieve 0° to 120° knee ROM by the end of week 6 and 0° to 135° by the end of week 8.^4,88,156 Also stretch tight musculature. Specifically evaluate the gastrocnemius, soleus, hamstring muscles, and IT band, because they have been shown to be tight in patients with PF dysfunction.²²⁴

• Improve muscle performance. Progress pain-free, closed-chain (bilateral minisquats, seated leg press) and open-chain resistance training to increase strength and muscular endurance of the entire lower extremity. Place emphasis on strengthening the knee extensors and hip extensors, abductors, and external rotators. (Suggestions for a progression of nonweight-bearing and weight-bearing exercises are noted in the previous section on nonoperative management and described in the final section of this chapter and Chapter 20).

PRECAUTION: Be certain to have the patient perform resisted exercises only in pain-free ranges and in positions consistent with weight-bearing precautions. During weight-bearing exercises, reinforce proper lower extremity alignment to avoid knee valgus during flexion.

• Improve neuromuscular control and response time, proprioception, and balance. While wearing the orthosis locked in extension, begin neuromuscular/proprioceptive training and stabilization and balance activities on a stable surface and then on unstable surfaces (minitrampoline, BOSU^®, or wobble board). Place emphasis on maintaining proper lower extremity alignment. Progress from bilateral to unilateral stance and from uniplanar to multiplanar movements. As knee control improves, unlock the orthosis during training.

• Improve cardiopulmonary endurance. Begin a stationary cycling program while wearing the range-limiting orthosis. Begin with a high seat adjustment and low tension. If wound healing is adequate, begin pool walking and marching or jogging in a pool.

  Criteria to progress. The following criteria should be achieved to advance to the final phase of rehabilitation.¹⁵⁶

• No swelling or extensor lag

• Knee ROM: 0° to 135°

• Sufficient strength of knee and hip musculature (at least 75% compared to nonoperated side) to initiate lower extremity functional activities

Exercise: Minimum Protection/Return to Function Phase

Goals and interventions. During the final phase of rehabilitation, which extends from 8 to 12 weeks and beyond, the patient gradually participates in more demanding functional activities without recurrence of pain, patellar instability, or joint effusion. By 12 weeks postoperatively, the patient should be able to begin land-based jogging and, by 16 to 20 weeks, return to a full level of activity without symptoms. Modification of some activities, however, may be necessary.⁴

Emphasize activity-specific training, always maintaining proper lower extremity alignment. Efforts should be made to modify the patient's lifestyle to avoid symptom-provoking activities, at least on a temporary basis. Develop and implement a self-managed program to continue to improve and maintain strength, flexibility, and balance, and devise a plan for adherence.

NOTE: Continued use of patellar taping or a patellar tracking orthosis during exercise may be useful during the progression of exercises and transition to high-demand functional activities.

Refer to the exercise progression previously discussed for advanced nonoperative management and selected exercises described in the final sections of this chapter and Chapter 20. More advanced exercises, including plyometric training and agility drills, are described in Chapter 23.

Distal Realignment Procedures: Patellar Tendon with Tibial Tubercle Transfer and Related Procedures

For a patient with recurrent subluxation/dislocation of the patella with or without degeneration of the lateral and distal articular surfaces of the patella, a procedure involving distal realignment of the extensor mechanism may be the surgical intervention of choice. A medial transfer and possibly anteriorization of the tibial tubercle decreases laterally directed forces on the patella to improve patellar tracking and shifts contact stresses in a medial and proximal direction away from chondral lesions of the distal and lateral articular surface of the patella.^47,86

Distal realignment procedures may be used in isolation or coupled with LRR or a proximal soft tissue procedure, such as MPFL repair or reconstruction or medial capsular reefing.^{47, 88,194}

Indications for Surgery

The following are indications for distal realignment procedures.^{47,86,87,179,194,216,226}

• Recurrent episodes of lateral patellar instability (dislocation/subluxation) and a sense of the knee "giving way" because of patellar malalignment due to lateralization of the tibial tubercle and patellar tendon insertion

• Painful lateral tracking of the patella with no instability

• Anterior knee pain associated with patellar maltracking and patellofemoral arthrosis (chondral or osteochondral defects) of the lateral and distal retropatellar surfaces

• Abnormally increased Q-angle

• Excessive tibial tubercle-trochlear groove distance (> 15 mm)

  CONTRAINDICATION: Boney procedures are not recommended for the skeletally immature patient whose tibial tubercle growth plate is open. Recurvatum of the knee can develop with premature closure of this epiphyseal plate.^86,114

Procedures

Background and Operative Overview

The purpose of distal realignment procedures is to reduce patellar instability and anterior knee pain by reducing laterally directed forces on the patella and improving patellar tracking.^{47,86,87,216,226} Distal realignment procedures are performed using an open surgical approach. However, arthroscopic examination of the knee joint, débridement of the articular surface of the patella, and sometimes an LRR precede the distal realignment procedure.

A number of surgical techniques for distal realignment have been reported.

Tibial tubercle transfer (Elmslie-Trillat procedure). An osteotomy of the tibial tubercle is performed; the boney prominence is then transferred medially and secured with screw fixation.^47,86,88

Anteriorization (elevation) of the tibial tubercle. Typically combined with a medial tibial tubercle transfer, this procedure involves displacing the tubercle anteriorly by means of a bone graft.²²⁶ This serves to reduce shear forces on the patella and offloads the articular surfaces of the distal patella.^47,86,226

Distal medialization of the patellar tendon. This procedure involves only a soft tissues transfer for the skeletally immature patient.

Complications

Uncommon but serious complications associated with distal realignment procedures include tibial fracture during placement of fixation screws, neurovascular injury during surgery, inadequate skin closure or sloughing over the osteotomy site, soft tissue infection or osteomyelitis, and nonunion of the transposed bone.^86,226 Redislocation can occur laterally because of undercorrection or medially with overcorrection, particularly in patients who return to high-demand activities.^86,194

Pain at the anterior tibial tubercle from the fixation screws is not unusual. Therefore, screws are removed routinely 6 to 12 months after surgery.⁸⁶ As with all patellofemoral surgeries, patellar adhesions can occur, restricting knee motion. Because distal realignment shifts retropatellar loads medially and proximally, excessive medialization of the tibial tubercle and patellar tendon (> 15 mm past the original insertion site) can cause excessive contact pressure on the medial patellar facet and medial compartment, contributing to arthrosis of these areas over time.⁴⁷

Postoperative Management

Immobilization and Weight-bearing Considerations

Depending on the type of fixation used, rehabilitation after distal realignment involving boney procedures must progress even more gradually than rehabilitation following proximal realignment of soft tissues to allow time for boney healing. Ambulation with crutches while wearing a knee orthosis locked in extension is permissible the day after surgery. Weight bearing is limited to touch-down/toe-touch for the first 4 weeks or until radiographic verification of bone callus formation at the osteotomy site has occurred.^86,156 Weight bearing is progressed gradually, with full weight bearing permissible without the immobilizer at 8 weeks if quadriceps control is sufficient.¹⁵⁶

Exercise Progression

ROM also is progressed more gradually than after soft tissue procedures. (Refer to exercise precautions noted in Box 21.7.) A range-limiting orthosis is worn that allows motion from only 0° to 30°¹⁵⁶ or 0° to 60°⁸⁸ of flexion during the first week to 90° of flexion by the end of week 4 to 135° by the end of week 8.¹⁵⁶ Closed-chain exercises are initiated in the range-limiting knee orthosis as increased weight bearing is permitted. Otherwise, exercises are similar to those for nonoperative management, LRR, and proximal realignment procedures. The return to full activity generally takes about 5 to 6 months and is based on bone healing and lower extremity strength.

Ligament Injuries: Nonoperative Management

Mechanisms of Injury

Ligament injuries occur most frequently in individuals between 20 and 40 years of age as the result of sport injuries (e.g., skiing, soccer, football) but can occur in individuals of all ages. The anterior cruciate ligament (ACL) is the most commonly injured ligament. Often, more than one ligament is damaged as the result of a single injury. Sprain and strain injuries of the knee are classified as knee instability and movement coordination impairments.¹⁴⁹

Anterior Cruciate Ligament

ACL injuries can occur from both contact and noncontact mechanisms (Fig. 21.12). The most common contact mechanism is a blow to the lateral side of the knee resulting in a valgus force to the knee. This mechanism can result in injury not only to the ACL but also to the medial collateral ligament (MCL) and the medial meniscus. This injury is termed the "unholy triad" or "terrible triad" injury because of the frequency with which these three structures are injured from a common blow (Fig. 21.13).

The most common noncontact mechanism is a rotational mechanism in which the tibia is externally rotated on the planted foot. Literature supports that this mechanism can account for as many as 78% of all ACL injuries.²⁰² The second most common noncontact mechanism is forceful hyperextension of the knee.

With prolonged ambulation on a knee that has a deficient ACL, the secondary restraints (lateral collateral ligament and posterolateral joint capsule) are stressed and become lax and a "quadriceps avoidance gait" may develop.¹¹¹ The quadriceps avoidance gait in ACL-deficient knees was originally documented and described by Berchuck and colleagues¹⁵ as a reduction in the magnitude of the flexion moment about the knee during the limb loading phase of gait due to the patient's effort to reduce contraction of the quadriceps.

Posterior Cruciate Ligament

Injury to the posterior cruciate ligament (PCL) (Fig. 21.14) most commonly occurs as the result of a forceful blow to the anterior tibia while the knee is flexed, such as a blow to the dashboard or falling onto a flexed knee. A study by Schulz²⁴⁷ evaluating 587 acute and chronic PCL-deficient knees reported that the three most common mechanisms of injury were a "dashboard"/anterior injury mechanism (38.5%), followed by a fall on the flexed knee with the foot in plantarflexion (24.6%), and lastly, a sudden, violent hyperflexion of the knee joint (11.9%).

Medial Collateral Ligament

Isolated injuries to the MCL can occur from valgus forces being placed across the medial joint line of the knee. Whereas most injuries to the ACL and PCL are complete tears of the ligament, injuries to the MCL can be partial or incomplete and are graded utilizing a I, II, III grading classification of ligament injuries described in Chapter 10 (see Fig. 21.13).

Lateral Collateral Ligament

Injuries to the lateral collateral ligament (LCL) are infrequent and are usually the result of a traumatic varus force across the knee. It is not uncommon that more than one ligament or joint capsule and sometimes the menisci are damaged as the result of a single injury creating posterolateral instability.

Ligament Injuries in the Female Athlete

With an increase in the number of female athletes since the passage of Title IX in 1972, a concurrent increase in the number of injuries to female athletes has been seen, most significantly an increase in the number of knee injuries. Interestingly, when injury to the ACL is sustained in a noncontact manner, a woman is three times more likely to tear the ACL than a man is.⁷ With the increased number of noncontact ACL injuries in female athletes being reported, the American Academy of Orthopaedic Surgeons published a consensus paper examining the risk factors and prevention strategies of noncontact ACL injuries.⁹⁸ In addition, clinicians and scientists interested in ACL-injury gender bias have met in retreat three times, the most recent in 2006, to present research, develop a consensus statement, and suggest future investigations on gender bias in ACL injuries.⁵³

Risk factors identified in these consensus papers fall into four major categories: biomechanical, neuromuscular, structural, and hormonal, and they are summarized here.^53,98

• Biomechanical risk factors include the effect of the total chain (trunk, hip, knee, and ankle) on ACL injuries, including awkward or improper dynamic body movements, deceleration, and change of direction. For example, increased hip adduction is related to increased knee valgus, which is associated with ACL injury risk in the female. Also, decreased hip flexion angles and knee flexion has been demonstrated during cutting activities in the female athlete.

• Neuromuscular risk factors have an influence on biomechanical factors in that neuromuscular control influences joint position and movement. Valgus collapse at the knee and decreased use of the hip extensors has been reported to be more common in women than in men who have sustained an ACL injury. It has been suggested that this is related to increased anterior shear of the tibia and strain of the ACL during loading (hip-knee flexion when landing following a jump).²²⁷ Not only are females weaker in hip and knee strength compared to males (normalized to body weight), but muscle timing and activation patterns of the quadriceps, hamstrings, and gastrocnemius muscles also differ between males and females.

• Structural risk factors include femoral notch size, ACL size, and lower extremity alignment. The femoral notch height is smaller and notch angle larger in the male compared to the female, which may affect ACL size. The female ACL is smaller than the male ACL, even when adjusted for body size. The ACL in the female has a lower modulus of elasticity (i.e., less stiff) and a lower failure strength (i.e., fails at a lower load); thus, the joint is more lax than in the male.

• Hormonal differences between males and females has also been postulated to be one possible factor related to the increased incidence of female ACL injuries. There are hormone receptor sites for estrogen, progesterone, and testosterone in the ACL of humans. The sex hormones have a time-dependency effect that influences ACL tissue characteristics, such as increasing risk of injury during the preovulatory phase of the menstrual cycle in females.¹⁴⁹

Common Structural and Functional Impairments, Activity Limitations, and Participation Restrictions (Functional Limitations/Disabilities)

• Following trauma, the joint usually does not swell for several hours. If blood vessels are torn, swelling is usually immediate.

• If tested when the joint is not swollen, the patient feels pain when the injured ligament is stressed.

• If there is a complete tear, instability is detected when the torn ligament is tested.

• When effused, motion is restricted, the joint assumes a position of minimum stress (usually flexed 25°), and the quadriceps muscles are inhibited (shut down).²⁷²

• When acute, the knee cannot bear weight, and the person cannot ambulate without an assistive device.

• With a complete tear, there is instability, and the knee may give way during weight bearing, which would prevent the individual from returning to specific work or sport and recreation activities that require dynamic knee stability.

Ligament Injuries: Nonoperative Management

Acute sprains, partial ligament tears, and sometimes complete rupture of a single knee ligament can be treated conservatively with rest, joint protection, and exercise. After the acute stage of healing, exercises should be geared toward regaining normal ROM, balance, a normal gait pattern, and strength, endurance, and neuromuscular control of muscles that support and dynamically stabilize the joint during functional activities.^64,77,117 The degree of instability following a ligament tear affects the demands the patient can place on the knee when returning to full activity.

A patient's preinjury activity level and the postinjury level of activity to which he or she expects to return influence the success of a nonoperative treatment program. Relatively sedentary individuals can usually function with some loss of knee stability and can expect to return to preinjury activities following a course of nonoperative management. For select athletes who wish to return to high-demand activities following ACL injury, an intensive rehabilitation program, including balance/perturbation training to stimulate neuromuscular control and develop dynamic knee stability, has been shown to be effective.^76,77 In contrast, for patients with extensive ligament damage or concomitant injuries (such as meniscus damage) and poor dynamic knee stability after a period of nonoperative treatment, surgical reconstruction typically is recommended to return to high-level work or sports and a preinjury level of function.

If the collateral or coronary ligaments are involved, because of their superficial location, they may benefit from cross-fiber massage, which helps align the healing fibers and maintain their mobility. Because of the structural characteristics of the MCL (a broad, flat ligament with deep and superficial portions, parallel alignment of collagen fibers, and fan-shaped attachments both proximally and distally), injuries to the MCL are typically managed with a conservative (nonsurgical) approach.³⁰¹ Conservative management of MCL injuries is described in Table 21.5; progression is based on presenting signs and symptoms.²⁰⁴ A similar rehabilitation program for ACL injuries is followed with appropriate precautions (as noted below) regarding stress to the ligament.

Nonoperative Management: Maximum Protection Phase

Follow the principles described for an acute joint lesion earlier in this chapter.

• If possible, examine before effusion sets in.

• Utilize cold and compression with rest and elevation.

• Teach protected weight bearing with use of crutches and partial weight bearing as tolerated.

• Teach safe transfer activities to avoid pivoting on the involved extremity.

• Initiate quadriceps-setting exercises. The knee may not fully extend for end-range muscle-setting exercises, so begin the exercises in the range most comfortable for the patient. As the swelling decreases, initiate ROM within tolerance.

Nonoperative Management: Moderate Protection (Controlled Motion) Through Return to Activity Phases

As swelling decreases, examine the patient for impairments and functional losses. Initiate joint movement and exercises to improve muscle performance, functional status, and cardiopulmonary conditioning.^64,149

Improve Joint Mobility and Protection

Joint mobility. Use supine wall slides (see Fig. 21.19), patellar mobilizations, and stationary cycling; encourage as much movement as possible. Unless there has been an extended period of immobilization, there should be minimal need to stretch contractures.

Protective bracing. Bracing may be necessary for weight-bearing activities to decrease stress to the healing ligament or to provide stability when ligament integrity has been compromised. Bracing can be one of two types: (1) range-limiting postoperative type braces that are used to protect healing tissues and then discontinued during later phases of rehabilitation; or (2) functional braces that are used during advanced rehabilitation and also when returning to functional activities. The patient must be advised to modify activities until appropriate stability is obtained.

Improve Muscle Performance

Strength and endurance. Initiate isometric quadriceps and hamstring exercises, and progress to dynamic strength and muscular endurance training. Quadriceps strength is important for knee stability.¹⁴⁹

• Utilize both open-chain and closed-chain resistance.

  • Open-chain resistance has been shown to be more effective for increasing quadriceps strength than closed-chain single-leg squat in patients with an ACL injury.²⁸²

  • Progress closed-chain exercises using partial squats, step-ups, leg press, and heel raises.

• Reinforce quadriceps contractions with high-intensity electrical stimulation if there is an extensor lag.²⁶⁷

Neuromuscular control. Neuromuscular control is compromised when stabilizing muscles fatigue.¹¹³ Emphasize neuromuscular reeducation (proprioceptive training) with stabilization, acceleration, deceleration, and perturbation training in weight-bearing positions.¹⁴⁹ Begin with low-intensity, single-plane movements and progress to high-intensity, multiplane movements. These exercises are described in Chapter 8 and summarized in the last section of this chapter.

Improve Cardiopulmonary Conditioning

Utilize a program that is consistent with the patient's goals, such as biking (begin with a stationary bike), jogging (begin with walking on a treadmill), using a ski machine, or swimming.

Progress to Functional Training

Develop activity-specific exercises and drills that replicate the demands of the individual's outcome goals.²⁸⁸ Suggestions for functional training are described in the exercise section of this chapter and Chapter 23.

Ligament Injuries: Surgical and Postoperative Management

Background

Ligaments of the knee provide the key stabilizing forces for accessory motions of the knee (see Fig. 21.2). Specifically, these accessory motions are anterior and posterior translation and medial/lateral pivots (valgus/varus/rotation). Strong ligamentous support is necessary, in part, because of the shallow design of the concave tibial articulating surface that allows significant translatory motions if unrestrained. Acute traumatic disruption or chronic laxity of the ligaments results in excessive accessory motions of the joint, which can impair functional abilities. Although injuries to each of the four primary knee ligaments (ACL, PCL, MCL, LCL) are discussed extensively in the literature, the ACL is, by far, the most frequently injured and surgically repaired.^19,202

General considerations and indications for ligament surgery. Factors influencing the decision for surgical reconstruction of a knee ligament include the ligament injured (differences in healing capacities among ligaments), the location and size of the lesion, the degree of instability experienced by the patient, the presence of concomitant pathology such as a meniscal or articular cartilage damage, and the potential for achieving the desired level of function to which the patient wishes to return.^{1,2,73,133,181,280} The risk of reinjury and prevention of future impairment are also considerations because acute ligament injury, if not managed adequately, can lead to chronic instability.¹⁹ In turn, chronic instability is thought to contribute to degeneration of articular cartilage over time and early-onset OA.¹⁵⁰

Surgical intervention for ligament injury is indicated if the patient has failed to achieve functional goals established in a conservative rehabilitation program or has early degenerative changes of the joint are apparent. Many authors^{19,32,83,181,258,280} recommend surgical intervention for acute, isolated ACL and LCL injuries after a brief period of acute symptom management in recreationally active individuals. Surgical management of chronic ligament deficiency is advocated when a patient's function has become compromised or when secondary pathology (e.g., meniscus damage, other ligament involvement, articular degeneration) has developed. However, there is no evidence to suggest that ACL reconstruction prevents or reduces the rate of progression of early-onset joint destruction.¹⁵⁰

Types of ligament surgery. Ligament surgeries are classified as intra-articular, extra-articular, or combined procedures and can be performed using an open, arthroscopically assisted, or all-arthroscopic approach.^32,141,181 Initially, intra-articular procedures were performed through an open approach and involved a direct repair of the ligament. The repair was accomplished by reopposing and suturing the torn ligament. Postoperatively, a long period (usually 6 weeks) of immobilization and restricted weight bearing were required because of extensive tissue disruption associated with the open approach and the poor healing qualities of ligamentous tissue.¹⁴¹ Outcomes were unacceptable due to postimmobilization contractures, patellofemoral dysfunction, muscle weakness, and an unacceptably high incidence of rerupture. Consequently, use of direct repair was abandoned as procedures involving intra-articular or extra-articular reconstruction were developed.

Intra-articular reconstruction of ligament injuries, which has evolved over the past four decades, has become the primary means by which ACL and PCL injuries are managed surgically. In general terms, reconstruction involves the use of a tissue graft to replicate the function of the damaged ligament and act as an inert restraint of the knee.^{20,32,141,158,181,199,280} Initially, intra-articular reconstruction procedures also were performed through an open approach. Although the reconstruction restored knee stability, the need for lengthy postoperative immobilization continued.¹⁴¹ Today, intra-articular ligament reconstruction is performed through an arthroscopically assisted or an all-arthroscopic approach, causing far less tissue morbidity and resulting in a more rapid postoperative recovery.

NOTE: Overviews of intra-articular ACL and PCL reconstruction procedures are described later in this chapter.

Extra-articular reconstruction procedures, which involve the transposition of dynamic musculotendinous stabilizers or inert restraints around the knee, such as the IT band, were designed to provide external stability to the knee joint. Extra-articular procedures, in common use in the past, particularly for MCL and LCL injuries, are used rarely today as primary procedures because they do not restore normal kinematics to the knee as effectively as intra-articular procedures. Use of extra-articular procedures to augment intra-articular reconstruction in difficult cases also has been shown to have little benefit.¹⁴¹

Grafts: Types, healing characteristics, and fixation. Intra-articular reconstruction is achieved through the use of tissue grafts, most often an autograft (the patient's own tissue) or occasionally an allograft (donor tissue) or a synthetic graft (Fig. 21.15).^{134,177,199,258} An allograft or synthetic graft is used only when a suitable autogenous graft is not available—for example, when a patient's own tissue is not suitable for graft harvesting.^141,199 However, there is concern that remodeling and incorporating the graft after implantation may be slower with an allograft (possibly due to sterilization to prevent disease transmission) or a synthetic graft than with an autograft.¹⁷⁷ (Refer to Chapter 12 and Box 12.9 for additional information about tissue grafts.)

Although a variety of tissues have been used for knee ligament reconstruction,^{134,143,158,177,186,199} a bone-patellar tendon-bone autograft has been used reliably and has been considered the gold standard for ACL reconstruction for several decades.^{32,71,141,143,203} It remains the most frequently selected graft material for this procedure.^{20,73,82,134,143,158,181} A frequently selected alternative to a patellar tendon graft for ACL reconstruction is a semitendinosus-gracilis tendon graft.^{71,141,143,186,254,281} Research has shown that the strength and stiffness of a bone-patellar tendon-bone graft and a quadrupled (four-strand) hamstring tendon graft are actually greater than that of the native ACL ligament.²⁵⁴

An extensive body of knowledge exists on graft healing, placement, and fixation as well as the strength and stiffness of various tissues selected as grafts and their responses to

imposed loads. Most research has focused on grafts for ACL reconstruction.^{20,29,82,133,143,264}

The need for a long postoperative period of immobilization and protected weight bearing after ligament reconstruction has been eliminated following primary ACL reconstruction because of advances in graft selection, preparation, placement, and fixation and because of the evolution of arthroscopic techniques.^20,29,264 Nevertheless, there is still a need to carefully select and progress the stresses imposed on the healing graft during early rehabilitation.

General considerations for rehabilitation. The expected outcomes following surgery and postoperative rehabilitation after ligament reconstruction are: (1) restoration of joint stability and motion, (2) pain-free and stable weight bearing, (3) sufficient postoperative strength and endurance to meet functional demands, and (4) the ability to return to preinjury activities.

Successful postoperative outcomes start, whenever possible, with a preoperative program that includes edema control, exercise to minimize atrophy and maintain as much ROM as possible, protected ambulation, and patient education.^{59,185,220,256} Preoperative intervention is often possible because ligament reconstruction typically is delayed until postinjury symptoms subside. Exercises are similar to those used for the early phase of nonoperative management of ligament injuries discussed in the previous section of this chapter. Depending on the location and extent of injury, an exercise program may be carried out for several weeks to several months before a decision is made to go forward with surgery.¹⁸⁵ Regardless of the duration of the preoperative exercise program, exercises should not further irritate the injured tissues or cause additional swelling or pain.

The progression and duration of postoperative rehabilitation programs published in the literature vary. No program has been shown to be optimal. Throughout rehabilitation, open communication with the surgeon enables the therapist to discuss any precautions or concerns specific to individual patients and procedures.

Regardless of the ligament injured or operative procedures performed, the emphasis of rehabilitation is placed on restoring a patient's functional abilities while protecting the healing graft and preventing postoperative complications and reinjury. Early controlled motion and weight bearing, hallmarks of current-day rehabilitation, have been shown to decrease the incidence of postoperative complications, such as contracture, patellofemoral pain, and muscle atrophy,^{220,256,259,303} and to allow patients to return to activity as quickly as possible without compromising the integrity of the reconstructed ligament.^193,259

For more than a decade there has been a move away from adherence to strict time-based rehabilitation protocols toward guidelines that are progressed based on the attainment of specific criteria and measurable goals or performance on functional tests.^{108,155,157,193,204,303} For example, an exercise program is progressed only after full, active knee extension has been achieved or arthrometer testing indicates that a particular level of joint stability is present. A criterion-based progression is advocated to ensure a safe return to high-level sporting activities and to prevent reinjury.^193,303

Anterior Cruciate Ligament Reconstruction

Unlike the MCL, which heals readily with nonoperative management, the healing capacity of a torn ACL is poor, giving rise to the frequent recommendation for surgical reconstruction to restore knee stability, particularly in the young, active individual.^19,133 Although the incidence of reinjury of the knee is lower after ACL reconstruction than with nonoperative management, particularly in patients younger than 25 years of age,⁶³ many individuals who have sustained an acute, primary ACL injury participate in a conservative course of treatment before a decision is made to undergo surgical reconstruction or to continue with nonoperative treatment.^64,185

Indications for Surgery

Although there are no rigid criteria for patient selection, the most frequently cited indications for ACL reconstruction include the following.^{19,32,158,181,185,186}

• Disabling instability of the knee due to ACL deficiency caused by a complete or partial acute tear or chronic laxity

• Frequent episodes of the knee giving way (buckling) during routine ADL as the result of significantly impaired dynamic knee stability despite a course of nonoperative management

• A positive pivot-shift test because an ACL deficit is often associated with a lesion of other structures of the knee, such as the MCL, resulting in rotatory instability of the joint

• Injury of the MCL at the time of ACL injury to prevent lax healing of the MCL

• High risk of reinjury because of participation in high-demand, high joint-load activities related to work, sports, or recreational activities

NOTE: Increased anterior translation of the tibia on the femur compared with the contralateral, noninvolved knee, as measured by an arthrometer, is considered a questionable indication because a strong correlation between these measurements of stability and a patient's symptoms of instability has not been established.¹⁹

CONTRAINDICATIONS: Relative, not absolute, contraindications for ACL reconstruction are noted in Box 21.8.^{19,32,158,186}

Procedures

Operative Overview

Surgical approach, graft selection, and harvesting. In the past 30 years, surgical management of the deficient ACL has evolved and continues to be refined with a move away from entirely open reconstruction to the current practice of most procedures now using arthroscopically assisted or endoscopic techniques to reduce tissue morbidity and reduce recovery time.^19,20,71,141 In an arthroscopically assisted approach, only the intra-articular portions of the procedure, such as meniscus débridement or repair, enlargement of the intercondylar notch of the femur, or drilling the femoral and tibial bone tunnels, are performed arthroscopically.¹⁴¹

The most common ACL reconstruction procedure today is an arthroscopically assisted or endoscopic procedure using an autograft. If a bone-patellar tendon-bone graft is selected, it is harvested through a small, longitudinal incision over the patellar tendon from the patient's involved knee^{20,32,73,158,181} or occasionally from the contralateral knee.²⁵⁸ The central one-third portion of the tendon is dissected along with small bone plugs attached to the tendon. If a semitendinosus-gracilis tendon autograft (hamstring tendon graft) is selected, it is harvested through an incision centered over the tibial insertion of the semitendinosus and gracilis tendons.^{71,186,254,261,264,273,281}

Although a summary of systematic reviews has shown no significant difference in outcomes following the use of bone-patellar tendon-bone versus hamstring tendon grafts if coupled with appropriate postoperative rehabilitation,¹⁴⁹ there are a number of advantages, disadvantages, and potential complications associated with these two classifications of autografts. For example, transition from mechanical fixation to biological fixation is thought to occur more rapidly with a patellar tendon graft, which involves bone-to-bone healing, than with a hamstring tendon graft, which requires tendon-to-bone healing (6 to 8 weeks versus 12 weeks, respectively).²⁶⁴ Other reported advantages and disadvantages of these two types of autografts are summarized in Boxes 21.9 and 21.10.^{1,71,141,143,162,241,254,261,273,281} It should be noted, however, that recently the use of a bone-hamstring tendon-bone autograft for ACL reconstruction was reported, allowing bone-to-bone healing and affording some of the same advantages associated with a bone-patellar tendon-bone autograft.¹⁶²

Graft placement and fixation. After the graft is harvested and prepared for implantation, the arthroscopic instrumentation is reinserted to drill femoral and tibial bone tunnels.^{20,83,141,158} Graft placement (see Fig. 21.15) is achieved by passing the graft through the tunnels to its final position in the tibia and femur. Precise, anatomical graft placement is crucial for restoration of joint stability and mobility. Improper graft placement can lead to loss of ROM postoperatively.¹ A graft placed too far posteriorly may result in failure to regain full flexion, and a graft placed too far anteriorly may limit extension.²⁹

NOTE: Limited ROM into extension also may be caused by graft impingement due to an inadequate femoral notch size or buildup of scar tissue in the notch.¹ A femoral notchplasty (enlargement of the intercondylar notch) is performed to ensure adequate clearance of the graft as the knee extends.

Graft fixation is vital to the success of ACL reconstruction. With a bone-patellar tendon-bone graft, the bone plugs are secured at each end in the prepared tunnels (bone-to-bone fixation) by means of screw fixation (metal or bioabsorbable interference screws).^{29,32,83,143,158,264} Several types of soft tissue fixation devices have been used to secure a hamstring tendon graft, including endobuttons, washers, and staples. Use of interference and transfixation screws also has been advocated.^{29,71,41,186,254} Despite these advances, strong tendon-bone fixation, particularly tibial fixation, remains a challenge.

An advantage of current-day fixation devices is that they can withstand early but controlled tensile forces placed across the graft with a low risk of compromising the security of the graft itself, provided proper placement and fit of the fixation devices are achieved.^20,29,71 This, in turn, permits early initiation of weight bearing and ROM of the knee, both typical elements of contemporary, accelerated rehabilitation programs.^{21,90,108,157,193,254,259,303}

After graft fixation and prior to closure, the knee is moved through the ROM to check the graft's integrity and the tension on the graft during knee movement. As with graft placement, proper graft tension at the time of fixation has a direct effect on postoperative joint mobility and stability. Too little tension can result in excessive knee laxity and potential instability, and too much tension can limit knee ROM.²⁰ After the incision is closed, a small compression dressing is immediately placed on the knee, and the leg may be placed in a knee immobilizer for protection.

Complications

There are a number of operative and postoperative complications that can compromise outcomes after ACL reconstruction. Some of these complications have been noted (see Boxes 21.9 and 21.10). Even minor technical errors during reconstruction can affect function adversely. As discussed in the previous section, inappropriate placement of the graft or bone tunnels, problems with graft harvesting such as inadequate graft length, and improper graft tension can adversely affect joint stability and mobility.^1,252 Insufficient graft length occurs more frequently during hamstring than patellar tendon graft harvesting. If graft fixation is insufficient, graft slippage and early failure can occur.^252,254 With a bone-patellar tendon-bone graft, a bone plug can fracture during harvesting or implantation, necessitating an alternative autograft or an allograft.²⁵²

Postoperatively, potential complications are knee pain, loss of motion, persistent strength deficits, and inadequate joint stability.^1,186,252 Anterior knee pain at the donor site of a patellar tendon graft or at the patellofemoral joint may affect functional activities. A neuroma of the infrapatellar branch of the saphenous nerve can cause significant knee pain during kneeling.

Loss of full knee extension and persistent quadriceps weakness are recognized as significant complications after ACL reconstruction, particularly if full extension is not achieved preoperatively.¹⁶³ There may be permanent damage to the extensor mechanism after patellar tendon graft harvesting, leading to quadriceps weakness or even patellar tendon rupture in rare instances. Limited ROM of the knee may have been present prior to surgery or may develop after surgery. One possible cause is a buildup of scar tissue in the intercondylar notch, necessitating arthroscopic notchplasty. Loss of patellar mobility also may be a source of limited knee ROM. It has been suggested that a patient's preoperative strength and ROM also may have an impact on postoperative knee motion and strength.

Lastly, graft failure and the need for revision reconstruction may occur even in the absence of risk factors related to surgical technique. It has been shown that graft failure is most likely to occur during the early months after surgery.⁸⁴ It has also been suggested that the most common cause of graft failure is poor adherence to postoperative rehabilitation, in particular returning to high-risk, high joint-load activities prematurely.^1,84,252

Postoperative Management

In the past, rehabilitation after ACL reconstruction involved long periods of continuous immobilization of the knee in a position of flexion and an extended period (often 6 to 8 weeks) of restricted weight bearing. Return to full activity often took a full year.^30,257 With advances in surgical techniques and a better understanding of graft healing and the impact of stress on the healing graft, early postoperative motion and weight bearing—often referred to as "accelerated rehabilitation"—has become the standard of care after primary ACL reconstruction with an autogenous graft for the active, typically young patient.^{21,36,90,108,157,193,217,220,256,257,303}

Accelerated rehabilitation is based on the premise that a precisely placed and appropriately tensioned graft not only is strong enough to withstand the stresses of early motion and weight bearing but also responds favorably to these stresses during the healing process.^{20,36,256,257,259,303}

Table 21.6 outlines a contemporary, accelerated program for postoperative management after primary ACL reconstruction. The sequence of goals and interventions identified in Table 21.6 and described in the phases of rehabilitation that follow reflects guidelines common to a number of programs published in the literature.^*

NOTE: It is important to recognize that although the descriptor "accelerated" is used frequently in the literature to characterize current-day rehabilitation after primary ACL reconstruction, there is no consensus on the initiation, progression, or duration of postoperative exercise, weight bearing, and other interventions.

Immobilization and Bracing

The rationale for a brief period of immobilization and the use of bracing in the early phase of rehabilitation after ACL reconstruction is based on protecting the graft from excessive strain and preventing the loss of full knee extension.^20,235,309 However, with advances in graft fixation, the need for and benefits of early versus delayed motion and/or protective bracing have become a point of debate—recommended by some but not by others.^{20,21,217,256,303}

Decisions about whether ROM is initiated early after surgery or postoperative bracing is prescribed are based on many factors. They include the surgeon's philosophy, the type of graft used, intraoperative observations about the quality of fixation, comorbidities and concomitant surgical procedures (e.g., meniscus or collateral ligament repair), and an assessment of the patient's expected level of adherence to a postoperative rehabilitation program.^108,220

Types of postoperative bracing. Protective bracing after ACL reconstruction falls into two broad categories: rehabilitative bracing and functional bracing.^20,235,309 Rehabilitative bracing, if prescribed, usually is a hinged, range-limiting orthosis with a locking mechanism. It is typically is worn for just the first 6 weeks after surgery. In contrast, a functional brace is worn when returning to high-demand sports or work-related activities to potentially reduce the risk of reinjury.

Brace use and initiation and progression of knee ROM. If a rehabilitative brace is prescribed after surgery, it may or may not be locked initially to hold the knee in full extension. (Even though the greatest stress on the graft occurs between 20° of knee flexion and full extension, precise graft placement and tension allow full knee extension without disrupting the graft's integrity.) If locked in full extension for a short period of time, the brace is unlocked for exercise as soon as ROM is permitted. It is worn throughout the day for a few weeks to 6 weeks²⁰ and sometimes is worn during sleep for protection for the first week postoperatively.²²⁰ Initially, the brace is locked in full extension during ambulation with crutches in the event of a fall.^{108,147,220,256,303} When ROM is initiated, the rehabilitative brace can be set to limit the range of knee flexion during exercise and functional activities so that flexion is progressed gradually.

Full, active knee extension and 90° to 110° of flexion is expected by 4 to 6 weeks postoperatively. The patient is weaned from brace use at about 6 weeks postoperatively if full extension has been achieved. Depending on the stability of the knee, sometimes the protective brace may need to be worn longer. These timelines are progressed more slowly when ACL reconstruction is combined with another procedure, such as a collateral ligament, meniscus, or articular cartilage repair.²¹⁷

Some patients are advised to wear a functional brace to reduce the risk of reinjury during the advanced phases of rehabilitation and when participating in high-demand sports or heavy manual labor after completing their rehabilitation program. However, the effectiveness of functional bracing after ACL reconstruction is unclear because the literature contains conflicting evidence.¹⁴⁹

Despite the widespread use of protective bracing following ACL reconstruction, the literature provides a critical analysis of its efficacy during early rehabilitation and when returning to high-risk activities.

Weight-Bearing Considerations

As with ROM, early weight bearing is possible after primary ACL reconstruction with a bone-patellar tendon-bone or hamstring tendon autograft because of advances in graft fixation. However, recommendations for a period of protected weight bearing immediately after surgery vary, ranging from some degree of restricted weight bearing the first 2 weeks to weight bearing as tolerated with use of two crutches immediately after surgery.^{21,71,147,193,217,241,256,288,303} Weight bearing is increased during the next 2 to 3 weeks based on the patient's symptoms. Protected weight bearing continues for a longer period of time if other structures in the knee have been injured and/or repaired (e.g., after repair of an articular cartilage defect of a femoral or tibial condyle).³⁰³

Full weight bearing and ambulation without crutches and with or without an unlocked protective brace usually is permitted by 4 weeks if weight bearing is pain-free and the patient has achieved full, active knee extension and sufficient strength of the quadriceps to control the knee.^{21,108,186,193,220}

Weight-bearing recommendations do not appear to be based on the type of graft or graft fixation used or whether protective bracing is worn but rather are determined on an empirical basis. The few randomized studies in the literature indicate that immediate and delayed weight bearing during the first few weeks after surgery produce similar outcomes.²⁰

Exercise Progression

A progression of carefully selected exercises and functional activities coupled with patient education is a foundation of rehabilitation following ACL injury and reconstruction.

Preoperative exercise. Because surgery typically is delayed after injury until acute symptoms have subsided, there is ample time to implement a preoperative exercise program to restore full knee ROM, particularly extension, prevent atrophy and weakness of thigh musculature, and improve the strength and flexibility of hip and ankle musculature.^{59,104,185,220,256,303}

Postoperative exercise progression. After reconstruction of the ACL, exercise begins immediately on the first postoperative day. Use of strong grafts, such as bone-patellar tendon-bone and quadrupled hamstring autografts, and reliable graft fixation make early motion possible.^{21,108,193,217,220,256,303}

Sometimes CPM is used while a patient is hospitalized or at home after discharge. Although a valid mechanism for controlling postoperative pain and initiating early motion,^164,256 it is used less frequently today than in the recent past.¹⁰⁸ Two recent systematic reviews indicate no additional long-term benefit with the use of CPM after ACL reconstruction.^266,310

The rate of progression of exercise and functional training after ACL reconstruction depends on many factors. For example, patient-related facts, such as age and preinjury health status, affect the healing process, enabling younger, healthier patients to progress exercises more rapidly. The type of graft and graft fixation also may influence the progression of exercise. Some resources advocate more rapid progression of exercise for bone-to-bone fixation with a patellar tendon graft than for tendon-to-bone fixation with a quadrupled hamstring graft, suggesting that bone-to-bone healing may be faster than soft tissue-to-bone healing.^108,220,303 In contrast, others advocate the same accelerated program for both procedures.^71,241,254

If, in addition to an ACL reconstruction, concomitant injuries are present or were managed surgically, the progression of exercises, as with weight bearing, typically is more gradual than after isolated ACL injury and reconstruction.²¹⁷

Exercises for progressive phases of rehabilitation after ACL reconstruction, summarized in Table 21.6, are described in the following sections. Exercise precautions are noted in Box 21.11.^{21,90,108,170,193,217,236,256,267,299,303}

Exercise: Maximum Protection Phase

During the early postoperative period, a delicate balance exists between adequate protection of the healing graft and donor site and prevention of adhesions, contractures, articular degeneration, muscle weakness, and atrophy associated with immobilization. Early motion places beneficial stresses that strengthen the graft but must be carefully controlled to avoid stretching the graft while in a weakened state, particularly during the first 6 to 8 weeks after implantation.