There are, not one, but two joints in the shoulder. The first is located where the collar bone meets the tip of the shoulder bone. This is called the acromioclavicular or AC joint. The junction of the upper arm bone (humerus) with the shoulder blade (scapula) is called the glenohumeral joint. Both joints may be affected by arthritis. The condition, however, is more common in the AC joint than in the glenohumeral joint.

Osteoarthritis does not affect the shoulder joint as much as it does the larger weight bearing joints of the body. It usually follows on from an injury to the shoulder or surgery to that area. Following shoulder trauma damaged ligaments may go undetected. This may lead, over time, to the development of bone spurs as the body tries to reduce joint motion.

Pain in the shoulder is the most common symptom of osteoarthritis of the shoulder. If the glenohumeral shoulder joint is affected, the pain is centered in the back of the shoulder and may intensify with changes in the weather. The pain of arthritis in the AC joint is focused on the front of the shoulder. The pain may be accompanied by limited motion. In advanced stages, the pain will be ongoing, making sleep difficult, The pain will also be triggered by even the slightest shoulder movement.

Initial treatment of osteoarthritis of the shoulder is geared towards pain management. The first step involves health and behavior modifications. Patient education, physical therapy, and exercise form the mainstays of these modifications. Bracing may also be applied to the affected area.

Drug therapies range from basic pain relief medications, such as aspirin and non-steroidal anti-inflammatories to Cox-2 specific inhibitors, opiates and stronger drugs.

Corticosteroid injections or injections of hyaluronic acid may also be given. Surgery, including arthroscopy, osteotomy and arthroplasty (joint replacement) will be considered as a last resort. Arthritis of the glenohumeral joint can be treated by replacing the entire shoulder joint with a prosthesis (total shoulder arthroplasty) or by replacing the head of the upper arm bone (hemiarthroplasty). The most common surgical procedure used to treat arthritis of the AC joint is a resection arthroplasty. In this procedure, a small piece of bone from the end of the collarbone is removed, leaving a space that later fills with scar tissue. Surgical treatment of arthritis of the shoulder is generally very effective in reducing pain and restoring motion.