The ACJ is the joint where your collar bone meets your shoulder blade, this helps to form a ceiling to the shoulder joint. It is not as mobile as the main shoulder joint (Gleno-Humeral joint, GHJ) and mainly works above shoulder height and when moving your arm across your body. It acts as a pivot point, helping with the movement of the shoulder blade allowing for greater rotation of the shoulder.
Types of injury – most injuries to the ACJ involve a fall onto the tip of the shoulder or FOOSH (Fall On Outstretched Hand). ACJ dislocation or separation is particularly common in contact sports such as rugby, martial arts and sports that have a high risk of falling such as horse riding, skiing or cycling. There are three main grades, grade 1 being a mild sprain to grade 3 which is a full separation of the joint. Physiotherapy treatment and rehabilitation is the first line treatment for grade 1 and 2 sprains, grade 3 sprains will likely need a surgical review. However, many grade 3 sprains go on to do very well without any surgical intervention following physiotherapy.