|The joint itself consists of only three bones - the femur (thighbone), tibia (shinbone) and patella (kneecap). Between the two long bones is sandwiched the shock-absorbing meniscus.||The cartilage-covered articulating surfaces of the three bones are sealed within the capsule, while the rest of the bone is outside capsule encloses the internal structures.||The capsule also encloses the anterior and posterior cruciate ligament, the menisci, any folds of the lining (plicae), and the Hoffa fat pad. The inner lining of the capsule secretes the joint fluid that lubricates the joint.|
Stabilising the knee joint
The joint is fundamentally unstable with the rounded ends of the femur articulating with the flat top of the tibia. The internal ligaments of anterior and posterior cruciate help to stabilise the knee in a front and back direction.
As the knee bends and straightens, the patella - which is embedded in the tendon of the quadriceps muscle - glides along a retaining groove in the femur. The patella is further stabilised by a fibrous network on either side - lateral and medial retinaculum - which has areas of thicker ligamentous fibrous tissue.
Outside the knee collateral ligaments support the joint from sideways movement. With the exception of the tendon of the popliteus muscle all the muscles and tendons of the knee are outside of the capsule.
The knee meniscus: structure-function, pathophysiology, current repair techniques, and prospects for regeneration. Makris EA, Hadidi P and Athanasiou KA. Biomaterials. 2011 Oct; 32(30): 7411–7431.
See also -
- Collateral ligament
- Cruciate ligament
- Fat pad
- Popliteus tendon
- Anterolateral corner
- Posterolateral corner
- Extensor mechanism