The acromion or bony roof of the shoulder joins with the end of the clavicle to form the acromioclavicular, or “AC” joint. The rotator cuff is a confluence of the tendons around the ball which passes beneath the acromioclavicular joint. The AC joint is often injured with falls onto the side or back of the shoulder or on the outstretched arm. When those injuries occur, the capsule and ligaments are damaged and the end of the collarbone or clavicle may become displaced or prominent on top of the shoulder. Occasionally, the collarbone may fracture very near the joint. Following the injury there may be significant pain over the end of the collarbone which is worse with attempts to move the shoulder or lift. These injuries are commonly referred to as a “shoulder separation”. Pain which is located directly over the collarbone, particularly if there is upward displacement, is diagnostic. Treatment is generally conservative with the use of a sling for a period of several weeks. Some injuries are more severe and may require surgical management, particularly if the clavicle is grossly unstable or there is an associated fracture. During surgery, the collarbone is brought down or reduced to its normal position with relationship to the acromion. It is generally supported in that position with a band that courses around the collarbone and then around the coracoid which is a bony prominence on the front part of the wing bone or scapula. Occasionally, a hamstring tendon graft from the leg may be harvested and used to support the repair, particularly if the surgery is delayed more than 4-6 weeks. Healing generally requires approximately 4 months after which time you may expect to return to full activities.