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  • Writer's pictureRandon Hall, MD

Acromioclavicular Injury (Shoulder Separation)


Acromioclavicular Injury, AC Sprain, Shoulder Separation


Typically occurs with a direct force to the outside aspect of the shoulder, such as a fall directly to the ground or being struck with a helmet. The injury occurs when the joint between the distal end of the clavicle and the shoulder blade becomes damaged. The attachment between the clavicle and shoulder blade is called the acromioclavicular joint (ac joint). It is secured by multiple ligaments, including the acromioclavicular ligament. As a side note, I prefer not to use the term shoulder separation, as it is an overly dramatic term to describe this condition.

Exam and Evaluation

Athletes will usually have swelling over the acromioclavicular joint and the front of the shoulder. Most individuals will not be able to lift the arm out in front of them or out to the side. If the injury is mild, limited range of motion and pain may be the only exam findings. One test is to bring the extended arm across the body to see if it causes pain at the AC joint (photo below). However, more severe injuries will often have a clear deformity and elevation of the distal end of the clavicle, either to touch or direct visualization. An x-ray is the optimal test to confirm the diagnosis, although it may be normal with mild injuries. One tip may be to get an x-ray that includes both ac joints to be able to compare the affected side to the unaffected side.


Using the modified Rockwood classification, there are six types of acromioclavicluar joint injuries. Type I involves a sprain or stretch of the acromioclavicular ligament. Type II involves a tear of the acromioclavicular ligament and mild elevation of the distal clavicle. Type III has complete tear of the supporting ligaments and 100% elevation of the distal clavicle compared to the unaffected side (photo above). Type V is similar to Type III, but the distal clavicle is more dramatically elevated. In a Type IV, the distal clavicle is pushed backwards, and in a Type VI the distal clavicle is pushed downwards.

Treatment Plan

The treatment depends on the position of the distal clavicle, as well as the age of the patient. Typically, Type I, II and III are recommended to be treated non-surgically. Non-operative treatment consists of sling immobilization for comfort. Keep in mind that a Type III may have significant deformity but is still treated without surgery. On the other hand, Type IV, V and VI are usually treated with surgical fixation to realign and stabilize the AC joint.

Return to Play

Return to play after an AC joint injury varies significantly based on the severity. Specifically, a Type I may only need a sling for a few days, and return can be as tolerated based on pain. However, Type II and Type III injuries may need around 4 to 6 weeks. One thing to consider is if the sport does not require the use of the upper extremity, return can be expedited, because it should not affect the ability to participate, as long as pain is well controlled. Athletes should consider alternative workouts during downtime with these injuries. If appropriate, athletes should consider cardiovascular workouts, such as jogging or stationary biking. Additionally, lower body strength training may be acceptable as well.

Acromioclavicular Joint

(Zoomed View)

Grade 3 AC Joint Injury​

Photo by @harlsta

Cross Body Test (Abduction Test)


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