Sternoclavicular Joint

The sternoclavicular joint is the synovial joint between the medial end of the clavicle and the upper part of the sternum, primarily the clavicular notch of the manubrium. The clavicle also articulates with the first costal cartilage at this joint. It provides the only direct bony articulation connecting the shoulder girdle and upper limb to the axial skeleton .^1,2

The sternoclavicular joint is classified as a saddle-shaped joint, although its articular surfaces are relatively incongruent. A fibrocartilaginous articular disc lies between the surfaces and divides the joint cavity into two compartments. The disc improves congruence between the joint surfaces and contributes to force transmission and stability .^1,2

Despite its relatively small size, the joint permits substantial movement of the clavicle. These movements include elevation and depression, protraction and retraction, and rotation around the clavicle's long axis. Motion at the sternoclavicular joint therefore contributes to positioning and movement of the scapula and shoulder during movements of the upper limb .^1,2

Because the bony surfaces provide limited inherent stability, the joint relies strongly on its capsule, articular disc, and surrounding ligaments. Important stabilizers include the anterior and posterior sternoclavicular ligaments, costoclavicular ligament, and interclavicular ligament. The sternoclavicular joint should not be confused with the acromioclavicular joint, which connects the lateral end of the clavicle to the scapula .^1,2