 Acromioclavicular joint dislocation is particularly common in collision sports such as ice hockey, football, Judo, rugby and Aussie rules, and is also a problem for those who participate in swimming, horseback riding, mountain biking, biking, snow skiing and skateboarding.The most common mechanism of injury is a fall on the tip of the shoulder or FOOSH (Fall On OutStretched Hand).Acromioclavicular joint dislocations are graded from I to VI.