The knee joint is formed by the distal femur, proximal tibia and the patella. There are ligament structures that provide stability to the bones: collateral ligaments and cruciate ligaments.

The entire surface of the knee is covered with a smooth structure called articular cartilage which allows a smooth gliding motion. Inside the knee joint there are two semicircular rings of cartilage called "menisci" that act as cushions. The synovial fluid is the lubricate that reduces joint friction.