The knee complex, formed by the tibiofemoral, tibiofibular, and patellofemoral joints, has little bony support and must rely on soft tissue structures to control the forces transmitted through the joints. The tibiofemoral joint is located between the body's two longest lever arms, the femur and tibia; these long lever arms exert extreme forces on ligaments and tendons. The knee relies on static stabilizers (ligaments) more so than dynamic support (muscles) and is more stable when the extremity is weight bearing than when it is not.
This chapter discusses injury to the knee and related muscles. The patella as it relates to the function of the tibiofemoral joint is described in this chapter. Conditions that are exclusive to the patellofemoral articulation are described in Chapter 11, and injury to the quadriceps and hamstring muscle groups is addressed in Chapter 12. The knee is functionally interdependent with the foot, ankle, hip, and trunk. Pathomechanics at these joints alter the biomechanical function of the knee. In the case of chronic knee injuries, these areas should also be examined.
The term "tibiofemoral joint" seems to imply that the knee involves only the articulation between the tibia and femur. In fact, the femur, menisci, and tibia all must function together. The patellofemoral mechanism (extensor mechanism) must also function properly to ensure adequate tibiofemoral mechanics. The proximal tibiofibular joint is functionally more influenced by the ankle joint.1
The femur, the longest and strongest bone in the body, is approximately one quarter of the body's total height.2 The femur's posterior aspect is demarcated by the linea aspera, a bony ridge spanning the length of the shaft (Fig. 10-1). As the femur reaches its distal end, the shaft broadens to form the medial and lateral condyles.
Anterior and posterior view of the femur. Note that the single anterior articular surface on the condyles of the femur 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. These structures have a discrete anteroposterior curvature that is convex in the frontal plane. The articular surface of the medial condyle is longer than that of the lateral condyle and flares outward posteriorly. 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 ...