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The knee capsule is a dual-layered structure that surrounds the knee joint. It is relatively thin anteriorly and posteriorly and thickened laterally by the collateral ligaments.
The outer layer of the knee capsule consists of fibrous connective tissue to hold the joint in place, whereas the inner layer consists of a synovial membrane which secretes synovial fluid into the joint to provides lubrication.
The femoral aspect of the capsule is demarcated by:
- the proximal femoral condyles and intercondylar fossa posteriorly
- patellar retinaculum anteriorly
- articular margin of the femur medially
- the femur just proximal to the groove for the popliteus tendon laterally
There is no capsule above the patella, allowing the suprapatellar bursa to communicate with the joint.
The tibial aspect of the capsule is demarcated by:
- the tibial condyles posteriorly and medially
- patellar retinaculum and tibial tuberosity anteriorly
- head of the fibula laterally
There is also an aperture for the popliteus tendon at the lateral tibial condyle.
The fibrous capsule also has a deep component with thickening on the medial aspect being part of the medial collateral ligament. The deep component also attaches weakly to the menisci, where they are known as the coronary ligaments 1.