The acromioclavicular joint is part of the shoulder joint. It is formed by the union of the acromion, a bony process of the shoulder blade, and the outer end of the collar bone or clavicle. The joint is lined by cartilage that gradually wears with age as well as with repeated overhead or shoulder level activities. The condition is referred to as AC joint arthritis or acromioclavicular joint arthritis.

What Causes AC Joint Arthritis?

AC joint arthritis is caused by the wearing out of the cartilage covering the bone ends of the AC joint. This may be due to excessive strain over prolonged periods of time, or due to other joint diseases, injury or deformity. Most commonly it is seen as a normal process of ageing, and in the majority of people does not cause symptoms. AC arthritis may also be the consequence of another disease or condition, such as AC joint separation.

What are the Symptoms of AC Joint Arthritis?

Symptoms generally include very localised pain or tenderness directly over the AC joint There may also be pain with certain motions, swelling, and clicking from the joint, and pain when lying on the affected side at night

How is AC Joint Arthritis Diagnosed?

When you present with the above symptoms, your doctor will review your medical history and perform a physical examination. An injection into the AC joint can temporarily reduce pain and can be very helpful at identifying the AC joint as the source of pain. Other tests your doctor may order include X-rays and an MRI scan of the shoulder. This can be very helpful to reveal cartilage and bone destruction and abnormal fluid accumulation within the joint and surrounding tissues..

How is AC Joint Arthritis Treated?

Your doctor will initially aim to treat your symptoms non-operatively, by instructing you to limit or modify your activities and by trying to control your pain. Pain is controlled by simple pain medication, anti-inflammatory medication, corticosteroid injections into the joint, and physical therapy. If symptoms persist, surgery may be recommended. Surgery is usually performed by a minimally invasive technique using arthroscopy. It usually involves removal of less than one centimetre of bone from the end of the collarbone (distal clavicle resection) to prevent the bones in the joint from rubbing against each other.

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