Synovial joints have two opposing surfaces covered with articular cartilage that are attached at their periphery by the joint capsule.
The synovium is the lining tissue of the capsule and originates at the periphery of the articular cartilage on both sides of the joint, coating the capsular structures. The capsule , along with its synovial lining, creates a pouch that contains synovial fluid secreted by the synovium. All intra-articular ligaments, such as the anterior cruciate ligament in the knee and ligamentum teres in the hip, are also surrounded by synovium. Intra-articular tendons, such as tendons of the long head of the biceps in the shoulder and the popliteus in the knee are also covered by synovial tissue. The unique structure of synovial joints permits the sliding of the articular surfaces with less friction than is created by ice rubbing on ice. Synovium is also found lining bursae and tendon sheaths. Similar to its function in the synovial joint, the synovium secretes fluid and allows the smooth passage of tendons through their sheath and decreases friction between a bony prominence and overlying skin or tendon.