The knee joint is the largest joint of the human body. It connects the upper leg with the lower leg. The leg has three partial joints, which are built of three bones (femur, tibia, fibula) and one kneecap (patella): medial articulation, lateral articulation and patellofemoral articulation (patella and patellar groove). The knee joint enables us to extend or flex the lower leg, and it is plays a part in the rotation of the foot as it can be rotated internally or externally. It makes movements like climbing stairs or sitting down on a chair possible.


The menisci are the shock absorbers and stabilizers of the knee joint. They are C-shaped, wedge-shaped in profile, and they are located between the joint surface of the femur and the tibia. Menisci can shift so that they can reduce the friction between bones and, thus, counteract wear and tear. The medial meniscus is linked to the lateral collateral ligament of the knee, which makes it less movable and more prone to injury compared to the lateral meniscus.


The knee joint is stabilized by strong ligaments: medial collateral ligament and lateral collateral ligament as well as anterior cruciate ligament and posterior cruciate ligament. The collateral ligaments support the knee when moving sideways.

The cruciate ligaments and collateral ligaments hold the knee joint together and stabilize it. Their main purpose is to secure the knee as they prevent it from shifting or turning too much forwards, backwards or sideways.

Joint capsule

The joint capsule, also called articular capsule, of the knee encloses the knee joint. It consists of a thin, white, shimmering membrane and produces the so-called synovial fluid, which is kind of a grease of the knee joint. The synovial fluid has to fulfil two tasks: it makes a smooth motion without any resistance possible, and it nourishes the cartilage.


Cartilage is a firm tissue that is elastic when bent or put under pressure. It surrounds the femoral and tibial heads.
During movement, bones do not grind into each other because there is cartilaginous tissue between them. Cartilage protects the bones so that a painless and unimpeded mobility of the knee is possible.


Like in every other joint, the knee also contains several bursae. Most often, the bursa right in front of the patella (kneecap) can cause problems. A swelling and inflammation of this bursa, which is called bursitis, can be a result of falling down on the knees, overtaxing the knee, especially when squatting down, or working on the knees (e.g., tiler).