From the Guidelines
The sternoclavicular joint is a saddle-type synovial joint. It connects the medial end of the clavicle to the manubrium of the sternum, forming the only bony attachment between the upper limb and the axial skeleton. This joint is classified as a saddle joint because the articulating surfaces are both concave and convex in different directions, similar to a saddle shape. The SC joint allows movement in multiple planes, including elevation/depression, protraction/retraction, and some rotation of the clavicle. Despite its small size, the SC joint is remarkably stable due to strong ligamentous support, particularly the costoclavicular ligament, sternoclavicular ligament, and interclavicular ligament. The joint also contains a fibrocartilaginous disc that helps absorb shock and improve congruence between the articulating surfaces. Understanding the SC joint's structure is important when evaluating shoulder mechanics and diagnosing conditions affecting the anterior chest wall and shoulder girdle. Some key points to consider about the sternoclavicular joint include:
- The joint's unique anatomy, which allows for a wide range of motion while maintaining stability 1
- The importance of ligamentous support in maintaining joint stability
- The presence of a fibrocartilaginous disc, which helps to absorb shock and improve joint congruence
- The potential for the SC joint to be affected by various conditions, including osteoarthritis, as mentioned in the differential diagnosis considerations for chronic non-bacterial osteitis (CNO) in adults 1.
From the Research
Joint Type
- The sternoclavicular joint is a saddle-shaped, synovial joint 2.
- It is the only skeletal articulation between the axial skeleton and the upper limb 2.
Characteristics
- The joint has a small surface area of contact protected by an intra-articular fibrocartilaginous disc 3.
- It is supported by strong extrinsic and intrinsic capsular ligaments 3.
- The function of load-sharing in the upper limb by bulky periscapular and thoracobrachial muscles is extremely important to the longevity of the joint 3.
Comparison with Other Joints
- The incidence of arthritis in the sternoclavicular joint is less than that in the acromioclavicular joint, suggesting that the extrinsic ligaments of the sternoclavicular joint provide greater stability than the coracoclavicular ligaments of the acromioclavicular joint 3.
Clinical Relevance
- Injuries to the sternoclavicular joint typically occur with high-energy mechanisms such as those obtained in automobile accidents or contact sports 4.
- Recognition and classification of these injuries are critical to proper management, thus minimizing potential long-term sequelae such as posttraumatic arthritis and recurrent instability 4.