What do the collateral ligaments do?
The collateral ligaments restrain the joint from forces that would open it up on the side, ie varus or valgus forces.
The medial and lateral collateral ligaments differ in size, and in their relationship to neighbouring structures.
The lateral collateral ligament is a pencil-like cord and stretches from the femur to the fibula. The medial collateral, in contrast, is flattened into a band with two layers - deep and superficial - the deep layer is attached to the medial meniscus, while the superficial layer attaches to the tibia, and these layers contribute to the joint capsule in this area. It contributes largely to stabilising the bent knee against against any force tending to force the joint open on the inner aspect (valgus force).
