Knee Joint Stabilisation Medial & Lateral Stability
Medial & Lateral Stability
Medial/lateral stability of the knee is provided for, once again, by static and dynamic soft tissue structures and by the tibial eminences and the menisci when the knee is in full extension. The knee is reinforced on its medial and lateral aspects by collateral ligaments and the collateral ligaments play a critical role in resisting varus/valgus stresses, especially in the more extended knee.
The tibial collateral ligament is a strong flat band that extends from the medial epicondyle of the femur to the medial condyle of the tibia and to the medial surface of the shaft of the tibia. It is a primary restraint to valgus angulation at the knee (resistance to knee going inwards or foot going outwards).
The lateral collateral ligament is a rounded cord approximately 5cm long and is the primary restraint to varus angulation at the knee (knee going outwards or foot going inwards). Superiorly it is attached to the lateral epicondyle of the femur, above and behind the groove of the popliteus muscle. It ends inferiorly 1cm below the apex at the head of the fibula on the lateral side.
Both cruciates also contribute to medial/lateral stability. As the knee flexes (bends) the dynamic stability provided by the musculature such as the muscles of the pes anserinus on the medial aspect of the knee become increasingly important. Naturally the ilio-tibial band, the lateral collateral ligament, the popliteus tendon, the biceps tendon, the postero-lateral capsule and the lateral head of gastrocnemius are all important factors contributing to stability. The postero-lateral capsule is particularly important to varus stability in extension whereas popliteus is the major stabiliser in the 0 to 90° of flexion range.
The menisci are also important to medial/lateral stability because the knee remains stable in full extension regardless of sectioning of ligamentous structures. Removing both menisci would appear to have its greatest effect in stabilisation during varus and valgus stresses (inward and outward stresses on the foot respectively).
