Rockwood grade I and II acromioclavicular injuries: as benign as commonly believed?

The acromioclavicular (AC) joint is the articulation between the distal clavicle and the acromion process of the scapula. As the upper limb moves, passive motion of the AC joint occurs in three planes, with the AC and coracoclavicular ligaments providing stability. Injuries are common, particularly during contact sports, and are classified using Rockwood's system. Grade I (sprain) and II (rupture) injuries only affect the AC ligaments and are generally managed conservatively. However, recent reports have indicated that long-term outcomes after these injuries are poor, perhaps due to an inadequate period of immobilization preventing complete ligamentous healing.