The intraarticular disk ligament is a very dense, fibrous structure that arises from the synchondral junction of the first rib to the sternum and passes through the sternoclavicular joint, which divides the joint into two separate joint spaces. The upper attachment is on the superior and posterior aspects of the medial clavicle. DePalma has shown that the disk is perforated only rarely; the perforation allows a free communication between the two joint compartments. Anteriorly and posteriorly, the disk blends into the fibers of the capsular ligaments.
The disk acts as a checkrein against medial displacement of the inner clavicle.
– Disorders of the Shoulder: Diagnosis and Management, 2nd Edition 2007 Lippincott Williams &Wilkins