The sternoclavicular (SC) joint is susceptible to injury from acute blunt trauma from motor vehicle accidents and contact sports such as football and rugby as well as repetitive microtrauma from activities that require repeated thrusting of the arm forward to grab objects off an assembly line or shrugging of the shoulder when reaching overhead in close quarters. Left untreated, the acute inflammation associated with the injury may result in arthritis with its associated pain and functional disability. Patients suffering from SC joint dysfunction or inflammation will complain of a marked exacerbation of pain when they perform activities that require thrusting the arm forward and retracting or shrugging the shoulder. A grating or grinding sensation with joint movement is often noted, and the patient frequently is unable to sleep on the affected side. Patients with SC joint dysfunction and inflammation will exhibit pain on active protraction or retraction of the shoulder as well as with raising of the arm high above the head. Palpation of the SC joint often reveals swelling or enlargement of the joint secondary to joint effusion. If there is disruption of the ligaments that surround and support the SC joint, joint instability and a cosmetic defect may be evident on physical examination (Fig. 82.1).

Plain radiographs and computerized tomography are indicated in patients suffering from SC joint pain (Fig. 82.2). They may reveal narrowing or sclerosis of the joint consistent with osteoarthritis, widening of the joint consistent with ligamentous injury, or frank dislocation (Fig. 82.3). They may also reveal occult fractures or primary or metastatic tumors as the joint is subject to invasion from malignant thymomas. If joint instability, infection, or tumor is suspected or detected on physical examination, magnetic resonance imaging, computerized tomography, and/or ultrasound scanning is a reasonable next step. Ultrasound-guided SC joint injection can aid the clinician in both the diagnosis and treatment of SC joint pain and dysfunction (Fig. 82.4).

The SC joint is a double gliding saddle-type synovial joint with an intra-articular disc separating the medial end of the clavicle and manubrium of the sternum (Fig. 82.5). Articulation occurs between the sternal end of the clavicle, the sternal manubrium, and the cartilage of the first rib with only ˜50% of the medial end of the clavicle actually articulating with
the manubrium of the sternum. Because of this, the joint is inherently unstable, with the inferior portion of the joint most subject to subluxation or dislocation. The joint is reinforced in front and back by the SC ligaments. Additional support is provided by the costoclavicular ligament, which runs from the junction of the first rib and its costal cartilage to the inferior surface of the clavicle. Additional strength is provided by the joint capsule. The joint is dually innervated by both the supraclavicular nerve and the nerve supplying the subclavius muscle. Behind the SC joint are a number of large arteries and veins, including the left common carotid and brachiocephalic vein and, on the right, the brachiocephalic artery. These vessels are susceptible to needle-induced trauma if the needle is placed too deeply or trauma from the elements of the joint should the joint be dislocated posteriorly due to blunt trauma to the anterior chest. The serratus anterior muscle produces forward movement of the clavicle at the SC joint, with backward movement at the joint produced by the rhomboid and trapezius muscles. Elevation of the clavicle at the SC joint is produced by the sternocleidomastoid, rhomboid, and levator scapulae. Depression of the clavicle at the joint is produced by the pectoralis minor and subclavius muscle. On palpation of the joint, a small indentation can be felt where the medial clavicle abuts the manubrium. The volume of the SC joint space is small, and care must be taken not to disrupt the joint by forcefully injecting large volumes of local anesthetic and corticosteroid into the intra-articular space when performing this injection technique.