Anatomy of the Knee
The knee joint is made up of four bones; the femur (thigh bone), the tibia (shin bone), the patella (knee cap) and the fibula. The knee is held together by special thick structures called ligaments (e.g. the anterior cruciate ligament (ACL)), in addition to the joint capsule and the strong muscles of the thigh and calf. The ends of the femur and tibia, and the undersurface of the patella, are covered with a smooth, gliding surface called articular cartilage (joint surface). The articular cartilage is protected by two rubbery shock-absorbing structures called the medial meniscus and lateral meniscus.