The knee is a joint made of three bones : the femur (thigh bone), the tibia (shin bone) and the patella (knee cap). In the joint, the surface of these three bones is covered with a layer of cartilage which allows the bones to glide against each other.

Menisci are small C-shaped tough cartilage that sit between the femur and the tibia . Menisci provide a rubbery shock absorber between the bone cartilages. They distribute weight and contribute to the stability of the knee.

The knee joint is a complex structure which is supported by four main ligaments that provide stability in all activities.

The collateral ligaments are lying outside of the knee and are called medial and lateral ligaments.

Two ligaments are lying inside the knee and are called the anterior (ACL) and posterior (PCL) cruciate ligaments. They cross each other inside the knee.

The anterior cruciate ligament provides stability when the knee is twisted between the foot being fixed onto the ground and the body twisting above it.. This happens usually in sporting activities with "pivot" : football, handball, ski ...

The collateral ligaments are lying outside of the knee and are called medial (C.M.L.) and lateral (C.L.L.) ligaments.