The acromio-clavicular joint is the joint between the end of the collar bone and the shoulder blade. It is commonly injured by direct trauma to the point of the shoulder (e.g. falling off a bike etc- see FRACTURES). It is also a common source of pain from degenerative arthritis.
Degenerative problems in this joint often present with pain directly over the top of the shoulder on the joint, rather than over the regimental badge area. Such pain is made worse with high arc movements, with the arm across the body and often at the extremes of internal roation (hand behind the back). An X-ray will normally confirm the clinical suspicion.
Treatment starts with simple pain killers and physiotherapy, though with established degenerative change the symptoms are often persistent. If so, an injection of anti-inflammatory into the joint may be required to settle the pain. In my hands this is often done with local aneasthetic under X-ray control as it can be a difficult joint to get into.
For persistant problems surgery can involve excision of a small piece of the end of the collar bone in the joint, which usually works well in relieving pain. This can be done arthroscopically (key hole) or through a mini-open incision.
Physio for ACJ problems can be found with the following link. ACJ Physio