AC Joint Injuries: The Acromioclavicular Sprain

The AC (Acromioclavicular) Joint is a joint in the human body not directly linked with Associated Content, despite the name correlation. This joint in the shoulder is one of the more commonly injured areas in the area, and is normally referred to as a "separated shoulder". This article lays out assessment and treatment options for this injury.

The AC joint is a link between the shoulder blade (scapula) and the body. This joint link provides the only true connection from the trunk to the limb through the shoulder. Joining the acromion, which is a bony process off of the scapula and the clavicle (collarbone), this synovial joint is supported by several ligaments around a weak joint capsule. The coracoacromial ligament and the acromioclavicular ligament support this joint, and provide the stability that normally is found here. An injury to these ligaments will make the AC joint unstable and increase pain and dysfunctional motion at the shoulder itself.

There are three major ways that one might injure this joint. They are: 1) A fall on the shoulder that pushes the tip of the acromion down, 2) Repetitive overhead work and 3) Falling on a hand that is outstretched, pushing the force up through the acromion. It is important to remember there are other factors with any of these injuries that may require other medical attention.

As with any type of ligament, there are three degrees of sprain. Grade I sprains allow mild damage with no displacement of the joint. A Grade II sprain allows a rupture of the acromioclavicular ligament and a sprain of the coracoacromial ligament. There is a palpable displacement of the acromion and the clavicle with a Grade II sprain. A Grade III sprain involves a complete rupture of both the coracoacromial ligament and the acromioclavicular ligament, along with an easily observed displacement between the clavicle and acromion.

Any motion that compresses the joint will aggravate it the worst following an AC joint sprain. This would include overhead or across the body motion of the shoulder. Another visual clue to this injury is the observable "drop-off" in Grade II and III sprains between the acromion and the clavicle. The acromion is pushed down, the clavicle is pushed upward.

Radiological exam may not reveal much, they are not detailed or designed to show the joint capsule. The chronic, old injury to this joint may cause that patient to show degenerative changes in the joint.

Treatment is based on the type of sprain. In a Grade I sprain, the rehab is started as soon as tolerated, focusing on avoiding the areas of pain-overhead and across the body, and moving into passive motion/stretches and physical agents as needed and determined by the Physical Therapist. Strength training is resumed once pain symptoms are gone and deemed by your therapist.

Grade II sprains are sometimes treated the same as a Grade I sprain, but depending on the doctor, they may choose to immobilize the joint for a short period before the process as outlined above continues.

The Grade III sprain conservative treatment starts with 4-6 weeks of immobilization, and is slowly progressed from there with passive motion and scapular strengthening. Exercises that help to strengthen the muscles in the area, including the rotator cuff and scapular stabilizers are progressed as tolerated. The AC joint can also be repaired in a Grade III injury, and as far as the rehab, the conservative approach for the Grade III sprain still applies here.

The AC joint is a quiet area unless injured. Protection until the healing starts is important, bout we need to see a PT or other health care professional to assess and treat. I hope this sheds some light on the subject for you if your have the symptoms yourself or a family member or friend has the same complaints.