The AC, or acromioclavicular, joint is located at the top of the shoulder. The joint forms the junction between the outer end of the collarbone, or clavicle, and the curved upper section of the shoulder blade called the acromion. According to the American Orthopaedic Society for Sports Medicine, the most common problems that occur at the AC joint are arthritis, fractures and separations. Generally, most injuries heal with conservative treatment, but in some cases, surgery may be required.
Arthritis
Degenerative arthritis may develop in the AC joint as a result of a repetitive strain injury. Initial treatment for the symptoms of pain and swelling are RICE--rest, ice, compression and elevation. In addition, a physician may prescribe medications to reduce inflammation and pain. In cases where symptoms become chronic, cortisone injections into the joint may be necessary. Surgical removal of the end of the clavicle may be the only option for eliminating pain in some conditions.
Shoulder Separations
According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, a blow to the shoulder or a fall on an outstretched arm are the most common causes of a separation of the AC joint. The American Academy of Orthopaedic Surgeons (AAOS) categorizes separations by the degree of damage to the ligaments that reinforce and anchor the joint.
In a mild separation, the AC ligament is stretched or sprained, but there is no displacement of the clavicle. Treatment is conservative--a sling or immobilizer restricts movements; ice and medications relieve symptoms.
A more serious injury is a tear of the AC ligament combined with a sprain or mild tear of the CC, or coracoclavicular, ligament that anchors the collarbone to the shoulder blade. A bump may occur where the collarbone has been displaced. Treatment is conservative unless symptoms and deformity persist.
In a severe injury, both the AC and CC ligaments are torn, resulting in a separation of the collarbone from the shoulder blade. The displacement causes a marked deformity above the shoulder joint. If the AC joint does not heal with immobilization, surgery may be necessary to reconstruct the ligaments and to realign the joint.
Fractures
According to the AAOS, a complete tear of the AC joint in conjunction with a fracture of the clavicle is usually caused by a fall on the shoulder. Surgical repair may be necessary if healing does not occur with conservative measures or in cases where the fracture is severe.
Risk Factors
Separated shoulders are common injuries in contact sports such as football and hockey. MayoClinic.com advises sports such as downhill skiing, gymnastics and volleyball also present a risk. Among the sports that may cause repetitive strain injuries are baseball and weightlifting.
Rehabilitation
The AAOS notes rehabilitation is an essential component of both conservative and surgical treatments. Strengthening and mobility exercises will assist in restoring function to the AC joint and to the shoulder joint, which has also been immobilized. MayoClinic.com reports most people with a mild shoulder separation regain full function within a few weeks. Severe separations and fractures may take a few months to heal.
