The knee is the most complex and interesting joint in the human body, made up of the articulation between three bones; the femur, tibia and patella.

The surfaces of the three bones are covered with hyaline cartilage, which allows the bones to glide over each other. The joint space contains the medial and lateral menisci, two fibrocartilage structures anchored to the tibia, femur and joint capsule. It also contains the anterior and posterior cruciate ligaments which stabilise the knee in its complex movements.

To either side of the joint are the collateral ligaments which stabilise the joint against side to side force. Motion is controlled and driven by the quadriceps and hamstring muscles, some of the most powerful muscles in the human body. Various other structures, the quadriceps and patellar tendons, the medial and lateral retinaculum, the ilio-tibial band the gastrocnemius and popliteus muscles all have further vital roles in knee function.

The combination of structures creates an amazingly strong, supple and stable joint.