Overview
The sternoclavicular joint is a synovial joint between the medial end of the clavicle and the superolateral part of the manubrium of the sternum and the adjoining first costal cartilage. It is the only attachment of the upper limb to the axial skeleton.
Articulations
- Bulbous medial end of the clavicle
- Manubrium of the sternum
- Costal cartilage of the 1st rib
- The joint is separated into two compartments by a fibrocartilaginous articular disc. The articular disc is attached to the joint capsule.
Joint Capsule
Although the joint is considered synovial, the bony surfaces are covered atypically by fibrocartilage rather than hyaline cartilage. The capsule consists of a fibrous outer layer and inner synovial membrane.
- The fibrous layer extends from the epiphysis of the sternal end of the clavicle, to the borders of the articular surfaces and the articular disc.
- The synovial membrane lines the inner surface and produces synovial fluid (reduces friction between the articulating structures).
Ligaments
There are four major ligaments providing stability to the joint:
- Sternoclavicular ligaments (anterior and posterior) – these strengthen the joint capsule anteriorly and posteriorly.
- Interclavicular ligament – joins the sternal ends of each clavicle and attaches to the jugular notch of the manubrium.
- Costoclavicular ligament – binds the clavicle to the first costal cartilage and the adjacent end of the first rib. It is very strong and provides the majority of the stability of the joint.
Blood supply
Arterial supply to the sternoclavicular joint is from the internal thoracic artery and the suprascapular artery.
Innervation
The joint is supplied by the medial supraclavicular nerve (C3 and C4 from the cervical plexus) and the nerve to subclavius (C5 and C6).
Movements
- Elevation (shrugging) and depression of the shoulders – results in upward and downward movements respectively between the sternal end of the clavicle and the disc.
- Protraction (forward) and retraction (squaring the shoulders) of the shoulders – movements of the acromial end likewise cause reciprocal movements at the sternal end; these movements occur between the manubrium and the disc.
- Rotation of the shoulder (abduction of the arm above the head) – results in passive rotation of the clavicle as the scapula rotates (transmitted from the scapula to clavicle by the coracoclavicular ligaments.