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The knee complex is one of the most often injured joints in the human body. The myriad of ligamentous attachments, along with numerous muscles crossing the joint, provide insight into the joint's complexity. This anatomical complexity is necessary to allow for the elaborate interplay between the joint's mobility and stability roles. The knee joint works in conjunction with the hip and ankle joints to support the body's weight during static erect posture. Dynamically, the knee complex is responsible for moving and supporting the body during a variety of both routine and difficult activities. The fact that the knee must fulfill major stability as well as major mobility roles is reflected in its structure and function.

The knee complex is composed of two distinct articulations located within a single joint capsule: the tibiofemoral joint and the patellofemoral joint. The tibiofemoral joint is the articulation between the distal femur and the proximal tibia. The patellofemoral joint is the articulation between the posterior patella and the femur. Although the patella enhances the tibiofemoral mechanism, the characteristics, responses, and problems of the patellofemoral joint are distinct enough from the tibiofemoral joint to warrant separate attention. Despite its adjacent location, the superior tibiofibular joint is not considered to be a part of the knee complex because it is not contained within the knee joint capsule and is functionally related to the ankle joint; it will therefore be discussed in Chapter 12.

Case 11-1: Patient Case

Tina Mongelli is a 43-year-old female patient who presents to your clinic with complaints of knee pain with increased activity. Tina's chief complaint is pain in and around her right knee (pain at best: 2/10) that worsens when she plays tennis and during stair ascents and descents (pain at worst: 8/10). She has palpable pain along the medial aspect of her tibiofemoral joint line. She schematically indicates pain around her patella that she subjectively describes as being behind her patella. She is currently unable to jog, play tennis, and walk for more than 1 mile without discomfort. Tina's past medical history includes tearing her anterior cruciate ligament, medial collateral ligament, and medial meniscus on the right side when she was 24 years old. After 4 months of exercise in an attempt to delay surgery, she subsequently underwent surgical reconstruction of the anterior cruciate ligament with a patellar tendon autograft and a partial medial meniscectomy. The medial collateral ligament was left to heal on its own. Clinical testing of her right knee revealed increased laxity with a valgus stress test with no pain at the end of range, full tibiofemoral range of motion (ROM), a hypomobile medial patellar glide, and 80% quadriceps strength compared to her left side. Diagnostic images were obtained of Tina's lower extremities. Weight-bearing radiographs of the right limb revealed genu varum with moderate joint space narrowing in the patellofemoral and medial tibiofemoral compartments. What structural abnormalities do you think are contributing ...

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