Synovial Membrane of Articular Capsule of Knee Joint

Structure

The synovial membrane of the knee joint forms the internal surface of the articular capsule of the knee joint. It attaches to the articular margins of the femur, tibia, and patella and the edges of the menisci. The synovial membrane lines the fibrous layer of the joint capsule both laterally and medially; however, centrally it becomes separated from the fibrous layer. This allows the synovial membrane to form folds, or plicae, which extend into the joint cavity (Boles and Martin, 2001).

Three commonly encountered plicae include the superior, medial, and inferior plicae.

—The superior (or suprapatellar) plica extends above the patella, behind the quadriceps tendon, and towards the suprapatellar bursa. The lining of this bursa is continuous with the synovial membrane of the knee joint (Moore, Dalley and Agur, 2013).

—The medial plicae (or plica synovalis) lies underneath the medial patellar retinaculum and extends laterally to the medial edge of the patella, while inferiorly it inserts into the infrapatellar fat pad.

—Two folds of synovium projects as two fingers either side of the infrapatellar fat pad, known as the alar folds. These folds merge posteriorly forming a single inferior plica (or infrapatellar fold or ligamentum mucosum).