What Is AC Impingement?

Since your shoulders are one of the most movable joints in the body, they are prone to injury and movement dysfunction due to poor movement patterns and overuse. AC impingement, referring to the irritation or inflammation of the acromioclavicular joint in the shoulder, is a common disorder among people who perform repetitive overhead movements with their arms and shoulders, such as tennis and volleyball players. With the right treatment and prevention strategies, you can reduce your risk of getting AC impingement.

  1. Functional Anatomy

    • The AC joint is on top of the shoulder between the acromion, which is the part of the shoulder blade that forms the highest part of the shoulder, and the clavicle (collarbone). Its primary function is to move your arm over your head. The AC joint serves as a pivot and gliding point for the joints to move. Both bones are connected by the acromioclavicular (AC)ligament.

    Causes and Symptoms

    • Every time you raise your arm up, there is some rubbing between the rotator cuff tendons and the bursa between the tendons and the acromion. Performing numerous repetitive movement patterns that require moving your arm over your head can cause irritation and impingement to the bursae, which are small sacs filled with synovial fluids that cushion bones and tendons. This can cause the bursa to swell and reduce the space between the acromion and rotator cuff tendons. If left untreated, this space reduction can cause bone spurs and calcification of the AC ligament, which will lead to early onset of arthritis and reduce mobility of the shoulder joint.

    Treatment

    • After a diagnosis, most orthopedic physicians would recommend taking anti-inflammatory medications or a cortisone shot to reduce the swelling and inflammation of the bursa, depending on the severity of your pain and AC impingement. Icing is another nondrug method to constrict the blood vessels in the AC impingement area, reducing the inflammation and pain.

      Surgery may be the last resort if you have severe pain that restricts your daily activities or if you have early-onset arthritis. The goal of surgery is to increase the space between the acromion and rotator cuff tendons by removing bone spurs under the acromion or part of the clavicle that attaches to the scapula (shoulder blade).

    Prevention

    • One of the best way to prevent AC impingement is to reduce the frequency of overhead movement patterns and recovery properly between training and practice days, suggests athletic trainer William Prentice, co-author of "Essentials of Athletic Training." Performing exercises that improve shoulder mobility and stability can prevent AC impingement and shoulder dislocation as well as improve athletic performance with a lower risk of injury. Consult with a qualified exercise professional or physical therapist to see what you can do to prevent shoulder injuries.