How the Normal Knee Works

The knee is the largest joint in the body, and one of the most easily injured. It is made up of the lower end of the thigh bone (femur), the upper end of the shin bone (tibia), and the knee cap (patella), which slides in a groove on the end of the femur. Four bands of tissue, the anterior and posterior cruciate ligaments, and the medial and lateral collateral ligaments connect the femur and the tibia and provide joint stability. Strong thigh muscles give the knee strength and mobility.

The surfaces where the femur, tibia and patella touch are covered with articular cartilage, a smooth substance that cushions the bones and enables them to glide freely. Semicircular rings of tough fibrous-cartilage tissue called the lateral and medial menisci act as shock absorbers and stabilisers.

An arthroscopic view of the medial compartment of the knee, showing the medial meniscus, medial femoral condyle and the medial tibial plateau.

An arthroscopic view of the medial compartment of the knee, showing the medial meniscus, medial femoral condyle and the medial tibial plateau.

An arthroscopic view of the medial compartment of the knee, showing the medial meniscus, medial femoral condyle and the medial tibial plateau.
An xray showing a normal knee (antero-posterior view).
An xray showing a normal knee (skyline view to show the patella).
A diagram showing the normal knee structures.
An xray showing a normal knee (lateral view).