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Ac joint sprainAC Joint Separation

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


Symptoms of an AC joint sprain will include pain right at the end of the collar bone. The pain my be widespread throughout the shoulder initially but later on more localized. Pain will be worse when trying to move the arm above the shoulder. There is often swelling and depending on the extent of the injury a deformity may be seen. This is an obvious lump where the joint has been disrupted and is visible on more severe injuries.

Acromioclavicular joint injury explained

The 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.

Grade 5 ac joint sprainThe 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.

Grade 4 ac joint sprainA 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.

Grading of injuries

Grade 1 AC joint sprainAC joint injuries are graded from 1-6 using the Rockwood scale which classifies injuries in relation to the extent of ligament damage and the space between the acromion and clavicle.

Grade 1 is a simple sprain to the AC joint with minor damage to the ligament and no separation of bones.

Grade 2 involves rupture of the AC ligament or acromioclavicular ligament.

Grade 2 AC joint sprainGrade 3 rupture of both AC and CC or coracoclavicular ligaments which often results in an upwards displacement of the clavicle bone.

From this point onwards the scale and grade of injury depends on the degree of displacement of the clavicle.

Grade 4 involves posterior displacement or displacement backwards.

Grade 3 ac joint sprainGrade 5 superior displacement, to a greater degree than grade 3, with an increase in coracoclavicular space by 3-5 times the norm. A step deformity may be apparent with grade 3, 4 & 5 injuries.

Grade 6 involves full rupture of both AC and CC ligaments with the clavicle being displaced inferiorly or downwards.


Cold wrap for the shoulderImmediate first aid for any AC joint injury is rest and apply ice or cold therapy. Immobilize the shoulder in a sling to ease pain by taking the weight of the arm. See a Sports Injury Specialist or Doctor. 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.

A sports injury specialist will diagnose the extent of the injury. 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

An 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.  Ultrasound for minor injuries, or TENS for pain relief can be used in more severe cases.

AC joint separation tapingA doctor may prescribe Anti-inflammatory such as ibuprofen medication to reduce pain and inflammation and advise on AC joint sepration exercises.

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.