The sternoclavicular (SC) joint has a critical role in the function of the shoulder, because it is a medial fulcrum of clavicular movement, having a wide range of motion and great force. However, the involvement of the joint has not been well documented. The purpose of the current study is to investigate the structure of the discus in the SC joint. Specimens from 20 joints of 10 cadavers were examined in this study. The specimens were decalcified and cut along the coronal plane. Each coronary sliced specimen was paraffin-embedded to be examined by histologically. Specific attention was given to the attachment between the discus and the intercalvicular ligament. The discus attached above the posterosuperior border of the clavicle and below the lateral end of the clavicular notch of the sternum. The superior part of the discus, together with the joint capsule, is inserted into the medial end of the clavicle and is thicker than the inferior one. The specimens in which the medial borders of the clavicles overhung the clavicular notch of the sternum showed the interclavicular ligaments connecting the superior and posterior borders of discus. In the specimens with a good joint congruity, the discus was attached with the periosteum of the clavicular notch of the sternum. The discus was perforated at the center of the inferior part in 5 specimens. The findings of this study suggested that the existence of the interclavicular ligament depended on the bony congruity of the SC joint and this ligament fibro-connecting with the joint capsule provided stability of the discus of the SC joint. The disc function is considered to be as a shock absorber within the joint. Our findings indicated that the forces along the lower part of discus during elevation or anterior-posterior rotation might result in the perforation of this part.
