Anatomy: The A-C joint sits on the top of the shoulder. It connects the Acromion process of the scapula to the clavicle or collarbone to support the shoulder
Injury: Patients may have pain from acute injury or simply from overuse
Diagnosis: Pain is present on palpation of this joint. A skilled shoulder examiner is required to identify this joint in many people. X-ray or MRI evidence of arthritis does not correlate with clinical pain. Patients may show extensive arthritis on these images and have no pain, or may have no findings on these images and have severe pain. The diagnosis is completely clinical. In questionable cases I will inject the joint with lidocaine as a test to verify the diagnosis.
Treatment: Physical therapy is usually not helpful and will usually aggravate the problem. Rest is beneficial. If pain persists we have had excellent results with PRP injection. Cortisone may also be used and has high short term efficacy but with a high recurrence rate. If pain is resistant or recurrent, arthroscopic distal clavicectomy is usually curative. This is a simple outpatient procedure in which about 7mm of bone is shaved from the end of the clavicle within the A-C joint. This eliminates friction in the joint and pain is generally eliminated.
A-C Joint Separation (Dislocation)
A direct fall on the shoulder can cause the acromion to droop such that the end of the clavicle produces an upriding prominence. In almost all cases pain goes away within several weeks and no further treatment is indicated. Recently some surgeons have recommended surgical reconstruction of the joint. However failure rates are high and the results are generally not better than simple observation without treatment – even in professional athletes (such as Luc Longley of the champion Chicago Bulls)