Acromioclavicular (AC) Joint Dislocation

Your acromioclavicular (AC) joint is located at the top outer edge of your shoulder. It connects your collarbone to the acromion, which sits at the highest point of the shoulder blade. The AC joint is one of four main joints in the shoulder.

A dislocation of the AC joint is called a shoulder separation. When the ligaments and other tissue holding the bones of the AC joint together are damaged, the collarbone and shoulder blade may separate. If you experience a shoulder separation, you may notice a bump or tenderness at the top of your shoulder. It may appear as if your collarbone is sticking out above the rounded corner of your shoulder, which now rests lower than the other shoulder.

Like a dislocation of the main shoulder joint, a fall or other direct trauma to the shoulder is the typical cause of an AC joint dislocation.

What Keeps the AC Joint Together?

The following helps to keep the AC joint stable and secure:

• Joint capsule – a thin fibrous layer that loosely encircles the AC joint; a synovial membrane lines the capsule’s inner surface, which produces fluid that lubricates the joint.
• Acromioclavicular (AC) ligament – strengthens the joint capsule.
• Coracoclavicular (CC) ligament – made up of the trapezoid ligament and conoid ligament and is the primary support for the AC joint.

Categories of Shoulder Separation Injury

Your orthopedic surgeon will categorize your injury according to the degree of damage to the ligaments supporting the joint, from mildest to most severe. Grades 1 – 3 are the most common AC joint injuries:

• Grade 1: This is considered a mild shoulder separation, when the AC ligament is sprained but otherwise looks normal on an X-ray. It involves a slight displacement of the joint. The CC ligament and joint capsule remain intact. This is the most common AC joint injury.
• Grade 2: This is a moderate shoulder separation, when the AC ligament and joint capsule are torn, but the CC ligament is usually only sprained. A grade 2 injury is considered a partial dislocation.
• Grade 3: This is a complete separation of the AC joint, in which the clavicle becomes dislocated from the shoulder blade, and both the AC and CC ligaments are torn.

Treating an AC Joint Dislocation

Most mild or moderate injuries to the AC joint will heal on their own after conservative treatment, such as immobilization (sling or brace), cold packs, pain and/or anti-inflammatory medication, and physical therapy.

If you or a loved one has experienced a grade 3 shoulder separation, in which the clavicle and shoulder blade are no longer connected at the joint, surgery may be necessary. This may involve repairing or reconstructing the damaged ligaments and joint capsule, or even trimming the clavicle bone, so it doesn’t rub against the shoulder blade.

AC Joint Dislocation Treatment in Knoxville and Athens, TN

Do you think your shoulder may have been separated? An AC joint dislocation can happen easily with trauma to the top outer edge of your shoulder. For the best medical care – and to get you back to your active life as quickly and safely as possible – call orthopedic surgeon Dr. David Hovis at The Shoulder Institute at ORTHOKnox at (865) 251-3030.