Articular disc of sternoclavicular joint

At a glance

English

Articular disc of sternoclavicular joint

Latin (TA2)

Discus articulationis sternoclavicularis

System

Cartilage

Region

Upper limb

Side

Paired, left and right

About the articular disc of sternoclavicular joint

The sternoclavicular joint is the only true joint connecting the upper limb to the trunk. It lies between the large, rounded medial end of the clavicle and the small clavicular notch of the manubrium, together with the upper surface of the first costal cartilage. The two bone surfaces fit poorly, and a strong fibrocartilage disc set between them makes up the difference. The joint is synovial, and the disc splits it fully into two separate compartments, each with its own synovial lining.

The disc is flat and roughly circular, thicker at its rim, especially at the top and back, than in the centre, which is sometimes perforated. Above and behind, it is fixed to the clavicle at the upper and posterior edge of its articular surface. Below, it is attached to the first costal cartilage close to where it joins the sternum. Around the rest of its edge it blends with the joint capsule and with the anterior and posterior sternoclavicular ligaments and the interclavicular ligament.

These attachments let the disc act as a strong check ligament. It prevents the medial end of the clavicle from riding upwards and medially over the manubrium when the shoulder is pushed down, as when carrying a heavy weight, and it cushions forces passed along the clavicle from the arm. The two compartments also allow different movements: elevation and depression take place mainly between the clavicle and the disc, and forward and backward movement between the disc and the sternum. The costoclavicular ligament, joining the clavicle to the first rib, is the main limit to these movements, and together they let the clavicle rotate along its long axis as the arm is raised.

Because the disc and ligaments are so strong, the clavicle usually breaks before this joint dislocates. When it does, anterior dislocation is more common and less serious; posterior dislocation can press on the great vessels, trachea or oesophagus behind the manubrium and needs urgent reduction. The joint can also be affected by osteoarthritis and, especially in people who inject drugs, infection.

Attachments and function

Attaches from

Attached above and behind to the upper and posterior rim of the joint face of the medial end of the clavicle.

Attaches to

Attached below to the first costal cartilage near the sternum, and around its edge to the capsule and the sternoclavicular and interclavicular ligaments.

Function

Separates the joint into two compartments, improves the fit of the surfaces, cushions load from the arm and stops the clavicle being driven upwards and medially over the sternum.

Nerve supply

The joint is supplied by the medial supraclavicular nerves and the nerve to subclavius.

Blood supply

Branches of the internal thoracic and suprascapular arteries supply the capsule and the disc margin.