How is the knee joint structured?

As a link between the thigh and the lower leg the knee joint comprises parts of two bone structures:

  • femoral condyle: curved (convex) lower end of the thigh
  • tibial plateau: recessed (concave) plateau in the tibia
Anatomy Knee Joint

When they are healthy the two parts of the joint are surrounded by a layer of joint cartilage which acts as a lubricant. The intra-articular space between the femoral condyle and the tibial plateau also contains the crescent-shaped menisci, which are made of cartilage. They alleviate pressure on the joint and thus protect the joint surfaces covered by cartilage.

The knee joint also includes the kneecap, which is a bone embedded in the knee extensor tendon. When the leg is stretched and flexed, the kneecap slides up or down and thus stabilises the knee joint at the front.

Role of the joint capsule

The fixed joint capsule forms an envelope around the knee joint to seal it off from the surrounding tissue. This capsule produces synovial fluid which serves to ensure friction-free movement of the knee joint and also supplies the joint cartilage with essential nutrients.

Stability and movement thanks to ligaments and muscles

The knee joint owes its stability to a complex set of ligaments:

On the inside and outside of the joint collateral ligaments provide stability, whilst the interior of the joint is stabilised by the anterior and posterior cruciate ligaments. As a result the knee is an extremely stable joint, despite the high forces acting on it. In addition, it is surrounded by powerful muscles which enable the legs to be moved with great force.