AC Joint Injuries in Contact Sport

The acromioclavicular (AC) joint sits at the top of the shoulder where the clavicle meets the acromion. It's a common site of injury in contact sport and cycling, typically from a direct blow to the top of the shoulder or a fall onto an outstretched hand. The good news is that most AC joint injuries are managed conservatively with excellent results.

Grading the injury

AC joint injuries are graded 1 through 6 based on which ligaments are torn and how far the clavicle has separated from the acromion. Grades 1, 2, and 3 are the most common and are generally managed without surgery. Grade 1 and 2 injuries involve partial ligament tears with minimal or no visible deformity. Grade 3 involves complete AC ligament rupture with a visible step deformity.

Conservative management

For grades 1-3, the evidence strongly supports non-operative treatment. Initial management involves a sling for comfort (typically one to two weeks), ice, and appropriate analgesia. Early movement is encouraged once the acute pain settles. Most grade 1 injuries are back to sport within one to two weeks; grade 2 within three to four weeks.

Rehabilitation

Once pain allows, rehabilitation focuses on restoring range of motion and rebuilding the rotator cuff and scapular stabilisers. The AC joint's role in transmitting force from the arm to the trunk means that weakness in these muscles puts ongoing stress on the joint capsule. Most athletes return to full sport at six to eight weeks for grade 2 and three and twelve weeks for grade 3.

The bump doesn't go away

It's worth knowing that the step deformity from a grade 3 injury typically remains permanently. This is cosmetic and does not affect function or long-term outcomes. Many athletes compete successfully at elite level with a visible AC joint bump.