Another common cause of pain around the top of the shoulder is Osteoarthritis of the ACJ. This is not uncommon and it may have been caused by a previous trauma (secondary osteoarthritis) or occur as a chronic degenerative disorder . In the latter cases the condition often co-exists with subacromial impingement. The pain is often very local to the ACJ, and certain movements will trigger the pain such as taking your arm across you body. However, as with a lot of shoulder conditions the pain can refer down the upper arm, towards the elbow and up towards the neck. Your physiotherapist will be able to identify if the ACJ is the cause of your symptoms or if it maybe contributing to them.