The knee complex consists of the tibiofemoral, proximal tibiofibular, and patellofemoral joints. For this chapter, the tibiofemoral joint is referred to as the knee. During activity, the knee is susceptible to a variety of acute and chronic injuries, many of which are related to its limited mobility and location. During weight-bearing activities, the knee moves through a large range of motion (ROM) while bearing a significant amount of weight. Independently and during double leg stance, the distribution of weight across the knees increases 3 to 4 times an individual’s body weight on level ground and 5 to 6 times when ascending and descending stairs.1
The knee joint is formed by articulations with the femur, tibia, and menisci. During movement, the knee is susceptible to rotational forces around the joint. The proximal tibiofibular joint is formed by the articulation of the tibia and fibula. Its function is to assist with torsional forces, and it provides stability to the knee during weight-bearing activities. The patellofemoral joint works in concert with the tibiofemoral joint during flexion and extension to ensure proper mechanics.
The femur, the longest and strongest bone in the body, is approximately one-quarter of the body’s total height (Fig. 10-1).2 At its distal end, the femur shaft broadens to form medial and lateral condyles. Due to the femur’s oblique position, the medial condyle is longer from its proximal to distal points than the lateral condyle.
Anterior and posterior view of the femur. Note that the single anterior articular surface on the condyles diverges posteriorly to form a lateral and medial compartment of the knee joint.
The medial and lateral condyles are covered with articular hyaline cartilage and articulate with the tibia via the menisci (Fig. 10-2). These structures have an anteroposterior curvature that is convex in the frontal plane. The condyles share a common anterior surface, then diverge posteriorly, becoming separated by the deep intercondylar notch. The femoral trochlea is an anterior depression through which the patella glides as the knee flexes and extends. The lateral and medial epicondyles arise off the condyles. The lateral epicondyle is wider and emanates from the femoral shaft at a lesser angle than the medial epicondyle. The adductor tubercle arises off the superior crest of the medial epicondyle. These prominences serve as attachment sites for tendons to improve the mechanical advantage of the muscle.
Articular structure of the knee. Oblique view of the left knee illustrating the articular relationship between the tibia, femur, and patella. The articulation between the femoral and tibial condyles is enhanced by the menisci (not shown). The tubercles of the intercondylar eminence align with the intercondylar notch.