Acromioclavicular (AC) joint arthritis, also known as AC joint arthrosis and osteoarthritis of the AC joint, is the wearing down of the cartilage in the AC joint. It is most often diagnosed in those in their 40s and older.

Unlike glenohumeral arthritis, or shoulder arthritis, which is the wearing down of the cartilage of the humerus (long arm bone) at the socket of the shoulder joint, AC joint arthritis is the wearing down of the cartilage at the acromion and the clavicle at the AC joint.

The primary cause for AC joint arthritis is general use. Though lifelong activities placing unusual stress on the shoulder joint, or earlier AC joint injuries such as shoulder separation, puts some at greater risk than others for the disease. Others more susceptible to the disease include workers who must use their arms for extended periods of time or athletes involved in overhead lifting. Blunt force to the shoulder, in either contact sports or in an accident, also leave a person susceptible.

Symptoms of AC joint arthritis include: pain and sensitivity at the front of the shoulder around the joint; discomfort when applying pressure to the area while sleeping; pain during certain arm and shoulder movements that may span the shoulder area, chest and neck; and swelling. Patients may also experience a reduction in range of shoulder motion.

After assessing a patient’s history and a physical examination, an X-ray will help show the degree of joint damage. And a series of X-rays can help determine the rate of progression.

Treatment is determined based on the affect the arthritis has had on a patient’s joint at the time of diagnosis, as well as the type of joint affected. It may involve conservative treatment – including cold compression, anti-inflammatory medications such as aspirin or ibuprofen, refrain from inflammatory activity, cortisone injections, and rehabilitation and occupational therapy to improve range of motion.

In more advanced cases nonresponsive to conservative treatment, either a resection arthropolasty or a complete shoulder replacement may be indicated.

The earlier the diagnosis, the greater the chance of preventing irreversible damage.