Shoulder pain is a frequent presenting complaint to physiatrists. Commonly encountered pathogeneses include rotator cuff pathology, bursitis, biceps tendonitis, and labral tears. Because the majority of shoulder pain originates within the subacromial region and the glenohumeral joint, the acromioclavicular, sternoclavicular, and scapulothoracic articulations may be overlooked. Osteoarthritis of the acromioclavicular joint is a common source of shoulder pain that is often neglected by clinicians and researchers. The proper diagnosis of acromioclavicular joint osteoarthritis requires a thorough physical exam, plain-film radiograph, and a diagnostic local anesthetic injection. Current treatment options are rather limited. Initial therapies are similar to that of osteoarthritis in other joints and include oral analgesics or anti-inflammatories and an emphasis on activity modification. Physical therapy, unfortunately, has little to offer, as therapeutic exercise and range of motion play only a minor role. If a diagnostic local anesthetic injection provides relief, there may be a role for corticosteroid injections. It seems that the administration of local corticosteroids into the acromioclavicular joint may provide short-term pain relief. The judicious administration of such injections remains controversial, and most experts agree that steroid injections do not alter the natural progression of the disease. Surgical options, indicated typically after a minimum of 6 mos of unsuccessful conservative treatment consist of open or arthroscopic distal clavicle resection.