The AC (acromio clavicular) joint is a small joint located at the top of the shoulder. It consists of two bones: the acromion is a part of the scapula (shoulder blade), and the clavicle (collar bone). There is a small space at the top of the shoulder where these two bones meet and it is commonly injured.

There are two main mechanisms for injuring the AC joint. The most common is a direct blow to the shoulder while the arm is away from the body (often from a fall or tackling in football). In this position, a direct blow pushes the acromion down causing a separation between the acromion and the clavicle, which can tear the ligament that lies between them. The other mechanism is falling on an outstretched arm. In this mechanism, the force of hitting the ground is transferred from the hand, through the arm, up into the shoulder and the AC joint receives the force. As a result the acromion and clavicle separate, causing the ligament to tear between the acromion and the clavicle.

One of the most common signs of an AC separation is a bump at the tip of the shoulder. This bump is the end of the clavicle. When the AC joint is separated, the clavicle will sit higher than the acromion. Normally they would be level. Another common symptom is pain at the AC joint when moving the arm across your chest. Besides a clinical exam, the best way to determine an AC separation is by getting x-rays. The x- rays will show if the acromion and clavicle are level or not. If they are level, the AC joint has been preserved. If they are not level, the AC joint has been sprained or separated. AC separations are rated in severity from I- VI; most occur are between I-III.

Mild AC separations are usually treated with conservative management consisting of ice, rest, anti- inflammatory medication and physical therapy. A sling should be worn initially for comfort and stability of the shoulder joint. In severe cases where non-surgical treatment fails, then surgery is indicated. Surgery for AC separations usually consists of repairing the ligaments that attach the clavicle to the coracoid (another spot on the scapula) and then excising (removing) the outer end of the clavicle bone.

After surgery, patients are typically in a sling for comfort and range of motion exercises start early, physical therapy is also done post- operatively. Total recovery time could be anywhere from one to eight weeks depending on the severity of the injury. Patients may return to their regular activities when the y have full range of motion without pain and full pain free strength. Athletes may return to sport after they have met the previous criteria and when they are able to perform sport specific activities without pain. A pad may be used to protect that area while playing sports.


  • AC Separations occur from a direct downward blow to the shoulder or from falling on an outstretched arm
  • Although AC Separations range in severity from I-VI, most range between I-III, and most do not require surgery.
  • Total recovery time from an AC Separation could be anywhere from 1-8 weeks depending on the severity of the injury.

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