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Acromioclavicular (AC) Joint Separation

Acromioclavicular (AC) Joint Separation


A shoulder separation is a fairly common injury, especially in certain sports. Most shoulder separations are actually injuries to the acromioclavicular (AC) joint. The AC joint is the connection between the scapula (shoulder blade) and the clavicle (collarbone). Shoulder dislocations and AC joint separations are often mistaken for each other. But they are very different injuries.

Acromioclavicular (AC) Joint Separation


The shoulder is made up of three bones: the scapula (shoulder blade), the humerus (upper arm bone), and the clavicle (collarbone). The part of the scapula that makes up the top part of the shoulder is called the acromion. The AC joint is where the acromion and the clavicle meet. One set of ligaments surrounds the AC joint, forming the joint capsule. Two other ligaments hold the clavicle down and attach it to a bony knob on the scapula called the coracoid process.

Acromioclavicular (AC) Joint Separation

The AC joint can be injured in different ways. The simplest type of injury is a simple sprain of the ligaments around the joint, normally referred to as a grade one injury. The injury is more severe when the ligaments around the joint actually tear (grade two injury). If the ligaments around the joint and the ligaments that attach the clavicle to the coracoid process tears, the injury results in an obvious bump on the shoulder (grade three injury).


The most common cause of an AC joint separation is falling on the shoulder (Fig. 3). As the shoulder strikes the ground, the force from the fall pushes the scapula down. The collarbone cannot move enough to follow the motion of the scapula. The ligaments around the AC joint begin to tear, dislocating the joint.

Acromioclavicular (AC) Joint Separation


The symptoms of AC joint separation range from tenderness over the joint to the intense pain of a complete dislocation. Grade two and three separations can cause a considerable amount of swelling. Bruising may occur several days after the injury. Grade three separations usually cause a noticeable bump on the shoulder.


Your doctor will need to get information about your injury and a detailed medical history. You will need to answer questions about past injuries to your shoulder. You may be asked to rate your pain on a scale of one to ten.

Diagnosis is usually made by the physical examination. Your doctor may move and feel your joint. This may hurt, but it is very important that your doctor understand exactly where your joint hurts and what movements cause you pain.

Your doctor may order X-rays. X-rays can show the dislocation, and they may be necessary to rule out a fracture of the clavicle. In some cases, X-rays are taken while holding a weight in each hand to stress the joint and show how unstable it is.

Non-Surgical Treatment

The majority of AC injuries do not require surgical treatment. Treatment for a grade one or grade two separation usually consists of pain medications and a short period of rest using a shoulder sling. Your rehabilitation program may be directed by a physical or occupational therapist. A permanent rehabilitation program for the AC joint may be needed.

Surgical Treatment

Surgery involves relocating the joint and repairing the torn ligaments (Fig. 4). This surgery is done through a four-to-five inch incision over the AC joint. A screw or some other type of fixation may be used to hold the clavicle in place while the ligaments heal. The screw is usually removed six to eight weeks after the surgery.

Acromioclavicular (AC) Joint Separation


If surgery is not needed, a physical or occupational therapist may recommend range-of-motion exercises that should be started as pain eases, followed by a strengthening program. At first, exercises are done with the arm kept below shoulder level. The program advances to include strength exercises for the rotator cuff and shoulder blade muscles.

After surgery, your doctor may have you wear a sling to support and protect the shoulder for a few days. A physical or occupational therapist will probably direct your recovery program. The first few therapy treatments will focus on controlling the pain and swelling from surgery. Ice and electrical stimulation treatments may help. Your therapist may also use massage and other types of hands-on treatments to ease muscle spasm and pain.

Therapists usually wait four weeks before starting range-of-motion exercises. You will begin with passive exercises. In passive exercises, the shoulder joint is moved, but your muscles stay relaxed. Your therapist gently moves your joint and gradually stretches your arm.

Active therapy starts six to eight weeks after surgery, giving the ligaments time to anchor solidly to the bone. Active range-of-motion exercises help you regain shoulder movement using your own muscle power. You may begin with light strengthening exercises that work the muscles without straining the joint.

After three months, you will start more active strengthening. Exercises will focus on improving strength and control of the rotator cuff muscles and the muscles around the shoulder blade. This helps the shoulder move smoothly during all your activities.

Recovery from shoulder surgery can take some time. You will need to be patient and adhere to your therapy program. Some of the exercises you’ll do are designed to get your shoulder working in ways that are similar to your everyday activities. Before your therapy sessions end, your therapist will teach you a number of ways to help avoid future problems.

  • American Orthopaedic Society for Sports Medicine
  • American Association for Hand Surgery
  • American Academy Of Orthopaedic Surgeons
  • The American Board of Pediatrics
  • North American Spine Society
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