Corpus: Sternoclavicular joint

The sternoclavicular articulation is the joint connecting the breastbone to the collar bone, linking the shoulder girdle to the trunk.

The sternoclavicular articulation is a saddle joint, though it is sometimes referred to as a functional ball-and-socket joint. It is formed by the articular surfaces of the manubrium of the sternum and the medial end of the clavicle, known as the sternal extremity of the clavicle. The articular surface of the clavicle is notably larger than that of the sternum. These two surfaces are separated by an articular disc, which divides the joint space into two halves, forming a dithalamic joint. Both surfaces are covered with fibrous cartilage to improve joint congruence. Several ligaments ensure joint stability, including:

• Anterior sternoclavicular ligament (capsule-reinforcing ligaments)
• Posterior sternoclavicular ligament (capsule-reinforcing ligaments)
• Interclavicular ligament
• Costoclavicular ligament: between the first rib and the clavicle

Dorsal to the sternoclavicular joint lies the venous angle, formed by the confluence of the internal jugular vein and the subclavian vein. The thoracic duct opens into the venous system on the left side, while the lymphatic duct opens on the right. On the right, the brachiocephalic trunk branches into the subclavian artery and the common carotid artery immediately dorsal to the joint.

This joint is the only bony connection between the upper limb and the trunk, allowing for three degrees of movement:

• Elevation and depression of the shoulder
• Protraction and retraction (forward and backward movement)
• Circumduction or rotation of the shoulder

Diseases of the sternoclavicular joint, such as osteoarthritis, are relatively rare. In cases of clavicle fractures, displacement of the joint can be a typical complication.