Acromioclavicular joint arthritis

The acromioclavicular joint (ACJ) contains a fibrocartilaginous disc, which may be involved in the degenerative process. Stability of the joint depends partly on the superior (stronger) and inferior (weaker) AC ligaments, and partly on the conoid and trapezoid ligaments that connect the coracoid and the clavicle.

Causes

• Primary osteoarthritis

• Post-traumatic arthritis (e.g. after Grade I and II ACJ disruptions)

• Distal clavicular osteolysis, due to repetitive microtrauma or fatigue failure associated particularly with weight training

• Rheumatoid arthritis, in which ACJ pathology may be an under-diagnosed cause of pain

Assessment

The main symptom is pain. This is usually well localized to the joint, in contrast to the distally radiating pain of subacromial impingement. The two diagnoses frequently coexist, however, and inferior osteophytes associated with ACJ osteoarthritis may contribute to impingement. Patients have pain on working with their arms raised, and examination reveals a high painful arc above 120° on both active and passive movements. The cross body adduction test also produces localized pain, and local anaesthetic ACJ injection is useful both diagnostically and in terms of predicting likely response to surgery.

The ACJ is seen on standard AP and axillary shoulder radiographs. The Zanca view may be useful for specifically imaging the AC joint. This uses an X-ray beam angled 10°–15° superiorly and a decreased kilovoltage to avoid the overexposure typically found on standard radiographs.

Management

• Conservative, with activity modification, NSAIDs, steroid injections, etc. Physiotherapy may be used, although there is little evidence for its effectiveness in ACJ arthritis

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