Synovial Joints - Accessory Structures

There are several types of accessory structures that may be present in synovial joints.

1. Accessory ligaments - these connect bone to bone and stabilize the joint by limiting motion in unwanted directions. Accessory ligaments may be capsular - a thickening of the joint capsule itself; extracapsular - outside the joint capsule; or intracapsular - inside the joint capsule.

2. Articular disks or menisci - these intervene between joint spaces. Examples are the lateral and medial menisci in the knee and the articular discs in the sternoclavicular joints.

3. Muscles and tendons - these can be very important for the integrity of many joints. Examples are the rotator cuff muscles in the shoulder which support the humerus and keep it in the glenoid fossa, and the popliteus muscle in the knee.