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, 11, 12, 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.
Structure and Function of the Knee
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).108 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.
Bones and joints of the knee and leg.
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.24,136
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 (MCL and LCL), respectively (Fig. 21.2).37,108
The medial meniscus is attached to the medial collateral, anterior cruciate, and posterior cruciate ligaments. The lateral meniscus is also attached to the posterior cruciate ligament. (Joint capsule removed for visualization). (From Hartigan, E, Lewek, M, and Snyder-Mackler, L: The knee. In Levangie, PK, and Norkin, CC (eds): Joint Structure and Function: A Comprehensive Analysis, ed. 5. Philadelphia: F.A. Davis, 2011, with permission.)