AC Joint Separation

Ac joint sprain

An AC joint separation or AC joint sprain is an injury to the ligament that holds the acromioclavicular joint together at the top of the shoulder. It is usually caused by fall onto an outstretched arm.

AC joint sprains range from very mild (grade 1) to a severe (grade 6) injury. Early treatment and support through taping is important to avoid long term problems or shoulder deformity.


Symptoms of include pain right at the end of the collar bone on the top of the shoulder. The pain my be widespread throughout the shoulder initially but later on more localized to a bony point on the top of the shoulder.

Pain will be worse when trying to move the arm overhead and there is often swelling and depending on the extent of the injury a deformity may be seen in the form of an obvious lump on top of the shoulder joint. Acromioclavicular joint separations are graded one to six with grade one being mild with only minor ligament damage and no separation of the bones whilst grade 6 is a severe injury with complete ruptures of the ligaments and visible deformity.

Read more on symptoms and diagnosis.

What is an AC joint separation?

Grade 5 ac joint sprainThe AC joint is short for the acromioclavicular joint. Separation of the two bones forming this joint is caused by damage to the ligaments connecting them. It is sometimes also referred to as a shoulder separation injury. The acromioclavicular joint is formed by the outer end of the clavicle or collar bone and the acromion process of the scapular or shoulder blade. The acromion is a bony process which protrudes forwards from the top of the scapular.

The two bones involved in an AC joint separation are attached by the acromioclavicular or AC ligament. There are several other ligaments which can be of importance in AC joint injuries, including the coracoclavicular or CC ligament which joins the clavicle to the coracoid process which is another forward protruding part of the scapula.

A third ligament involved in an AC joint injury is the coracoacromial ligament which attaches the acromion process to the coracoid process, although it is rarely involved in this type of injury. The most common way of injuring the AC joint is by landing on the shoulder, elbow, or onto an outstretched hand. The athlete falls and automatically places their hand out to break the fall. The forces are then transmitted up the wrist and arm to the shoulder joint.


Immediate first aid for any AC joint injury is to apply the PRICE principles of rest, ice, compression and elevation. Apply ice or a cold therapy and compression wrap as soon as possible to reduce pain and swelling. Wear a sling to immobilize the shoulder and ease pain by taking the weight of the arm.

A doctor may prescribe Anti-inflammatory such as ibuprofen medication to reduce pain and inflammation as well as diagnose the injury and assess how bad it is. If a bad AC joint injury is not properly treated it can lead to long term deformity in the form of a lump on top of the shoulder. Ultrasound for minor injuries, or TENS for pain relief can be used in more severe cases.

AC joint separation tapingAn AC joint taping should be applied which fixes and supports the joint into the correct position to assist with healing. The joint may need taping for 2-3 weeks. 

As pain allows shoulder exercises specifically recommended for AC joint sprain rehabilitation should be progressed.

Do I need surgery?

A grade 1,2 or 3 injury is usually treated conservatively without surgery. Grade 4,5 and 6 injuries and grade 3 sprains which do not respond to treatment usually require surgery

If this injury is neglected and allowed to heal out of place this could increase the wear and tear on your joint causing you problems in the future.