The shoulder is a complex and highly mobile joint. The acromioclavicular (AC) joint, located at the top of the shoulder, is a common site for arthrosis. AC joint arthrosis is a degenerative condition that can cause discomfort and limit daily activities. This article explains AC joint arthrosis, its causes, symptoms, and treatment options.
Understanding AC Joint Arthrosis
The acromioclavicular (AC) joint is located at the top of the shoulder, where the clavicle (collarbone) meets the acromion, the highest part of the scapula (shoulder blade). This joint is enclosed by ligaments that form a capsule, along with other ligaments that stabilize the clavicle by attaching it to a bony projection on the shoulder blade called the coracoid process. The articulating surfaces of these bones are covered with articular cartilage, a smooth, rubbery tissue that reduces friction and acts as a shock absorber during movement.
AC joint arthrosis, also known as osteoarthritis of the AC joint, occurs when this protective cartilage begins to break down and wear away. As the cartilage thins or disappears, the bones may rub directly against each other, leading to pain and changes in the joint. In some cases, abnormal bony growths called osteophytes, or bone spurs, can develop on the acromion and clavicle, which can further irritate surrounding tissues. This condition is more common in middle-aged individuals.
Recognizing the Signs
Pain and tenderness at the top of the shoulder, directly over the joint, are common signs of AC joint arthrosis. This pain is described as an aching sensation, but it can also be sharp, particularly with certain movements. Activities that involve bringing the arm across the chest or overhead motions exacerbate discomfort as they compress the joint.
Sleeping on the affected side can also trigger pain, disrupting sleep. Patients experience a decrease in their shoulder’s range of motion, making everyday tasks challenging. A clicking or grinding sensation may be felt or heard within the joint as it moves, and there can be noticeable swelling around the affected area.
Identifying the Causes
AC joint arthrosis is a degenerative “wear and tear” condition that develops over time due to repeated stress on the joint. Aging is a common factor, as cartilage naturally deteriorates with age. Continuous use of the arm and shoulder places stress on the AC joint, causing gradual wear.
Previous shoulder injuries, such as an AC joint separation or fractures, can contribute to arthrosis years later. Even after healing, such injuries can lead to accelerated joint degeneration. Repetitive overhead activities, often seen in weightlifters (especially with bench and military presses) or construction workers, also increase the incidence of the disease.
Treatment Approaches
Treatment for AC joint arthrosis begins with conservative, non-surgical methods to reduce pain and improve function. Rest and activity modification are recommended to alleviate stress on the joint, including avoiding activities that aggravate symptoms. Applying ice to the affected area helps reduce inflammation and pain.
Over-the-counter anti-inflammatory medications, such as NSAIDs, are used to manage pain and swelling. Physical therapy plays a role in conservative management, focusing on exercises to improve shoulder strength, flexibility, and range of motion without overstressing the AC joint. A physical therapist guides patients through specific movements to restore proper shoulder mechanics and reduce strain.
If conservative measures do not provide relief, corticosteroid injections directly into the AC joint are considered. These injections deliver anti-inflammatory medication to the affected area, offering temporary pain relief that can last for several weeks to months. However, these injections are not a long-term solution, and their frequency is limited.
When conservative treatments fail to alleviate persistent pain and functional limitations, surgical options are explored. A common procedure is distal clavicle excision, also known as the Mumford procedure. In this procedure, a small portion (5-10 millimeters) of the end of the clavicle is removed, creating a space between the clavicle and acromion to prevent rubbing and reduce pain. The procedure can be performed using an open incision or arthroscopically, which involves smaller incisions and specialized instruments. Recovery involves a period of rehabilitation to regain full shoulder strength and mobility.