The acromio-clavicular joint is the anatomical part of the shoulder where the collarbone joins the shoulder. It is commonly called the A/C joint or ACJ.
Pain and inflammation may occur as part of a sudden (acute) injury, or a recurrent overload (overuse) injury.
When overload and degeneration occurs, the ACJ often develops osteoarthritis. It may also develop osteolysis, where the end of the collarbone disintegrates as the bone starts to die.
ACJ degeneration is a progressive problem where there is localised pain in the ACJ area. Tenderness is localised to the tip of the shoulder and a swelling may develop. It is usually painful to lie on the shoulder or perform activities which compress the ACJ. These commonly include push-ups, bench press, overhead activities. Some people complain of clicking or grinding in the shoulder.
Management of ACJ degeneration is a step-by-step process:
- Diagnosis. An X-ray is essential to confirm existence of degeneration
- Reduce the load and reduce the inflammation. Changing work and exercise habits where possible. For pain relief the regular use of ice for the ACJ; the use of anti-inflammatory tablets or cortisone injections.
- Over a period of 2-3 months if there is no progress, surgery is an option. This is an excision of the distal (outer) clavicle and is now mainly performed through keyhole/arthroscopic surgery. The operation is known as an arthroscopic excision of the distal clavicle.
Injections to the Acromiclavicular Joint (AC Joint)The ACJ may be approached from different directions. Many favour an anterior approach (see below left), although the ACJ may be approached posterior or superiorly.
Standard hygienic precautions must be followed, and then a combination of 1 ml corticosteroid (cortisone) with 1 ml of local anaesthetic may be introduced.