KNOW YOUR KNEE
The knee is the largest synovial joint of the body. It is also one of the most complexes. The knee is composed of three bones (femur, tibia, and patella) and two articulations (tibiofemoral and patellofemoral).
The tibiofemoral joint is formed by two large, bulbous femoral condyles resting on a relatively ﬂat tibial plateau. As a result, it is inherently unstable. The movement at the knee joint is stabilized and limited by muscles (dynamically) and ligaments (statically). Accessory soft tissues such as the menisci, by virtue of their concave shape, increase stability of the knee joint by increasing the articular congruity the tibial plateau presents to the femoral condyles
The geometry of the articular surfaces also contributes to the knee joint’s stability (i.e., the concave femoral trochlea and convex patellar articular surface of the patellofemoral articulation)
There are two pairs of major ligaments (medial and lateral collateral ligaments, anterior and posterior cruciate ligaments) and many minor or capsular ligaments stabilizing the knee joint.
The medial collateral ligament and lateral collateral ligament lie parallel to the longitudinal axis of the knee. As such, they, respectively, prevent excessive valgus or varus displacement of the tibia relative to the femur.
The anterior cruciate ligament and posterior cruciate ligament lie intra-articularly and extra synovially in the midline of the knee .
The posterior cruciate ligament is about 50% larger in diameter than the anterior cruciate ligament. It has two functions. It acts as a linkage between the posterior cortex of the femur and the posterior cortex of the tibia about which tibial motion may occur, much like a gate hinge.
It prevents posterior displacement of the tibia on the femur.
The function of the anterior cruciate ligament can be deduced from its location within the knee. It is directed anterior to posterior and medial to lateral from near the anterior tibial spine to the posteromedial intercondylar aspect of the lateral femoral condyle. It prevents anterior displacement of the tibia on the femur. It “wraps around” the posterior cruciate ligament, becoming tighter with internal rotation of the tibia on the femur. As such, it also pre- vents excessive internal rotational movement of the tibia on the femur.