Orthopedics: Conditions

AC Joint Shoulder Separation

The shoulder is comprised of three bones: 1) the humerus (arm), 2) the scapula (shoulder blade) and, 3) the clavicle (collarbone). These bones form two joints: the shoulder joint (glenohumeral) and the AC (acromialclavicular) joint.

An AC joint shoulder separation occurs when the clavicle becomes dislocated from the roof of the shoulder (acromion). This results in severe pain, especially when attempting overhead movements or when swinging the arm across the body. Shoulder separations are usually caused by contact sports such as football. Injuries can vary from minor, as when only the acromioclavicular ligament is torn, to major, as when the coraclavicular ligaments are ruptured, affecting the entire shoulder.

There are three common types of separation injury (although there are more severe grades usually caused by major or life-threatening accidents). The typical sports injuries include:

  • Type I: stretching or slight tearing of the acromioclavicular
  • Type II: complete tearing of the acromioclavicular ligament
  • Type III: complete joint separation involving the tearing of the acromioclavicular ligament and the coraclavicular ligaments, causing the clavicle to push up so that the damage is visible on the shoulder


Symptoms vary with AC separation depending on the type of injury. They range from modest to moderate pain with arm movement, to severe pain and swelling at the joint, a popping sound, and pain with arm movement in the area of the coraclavicular ligaments.


The physician will first ask for a history of the patient’s injuries and symptoms followed by a physical exam. The doctor will compare the dislocated arm position to the "normal" side, examine the tissue and bone around the joint and perform range of motion tests on the arm.

Popping noises or a bump on the top of the shoulder may be indicators. To further determine the severity of injury, the physician may use the following:

  • An injection to block pain (which would indicate injury and provide relief)
  • X-rays (which can discriminate an AC injury from a fracture)


Most AC injuries for Types I, II and III are treated non-operatively. Rest and rehabilitation techniques usually have the same result after one year as surgical treatments, although the patient may have to experience discomfort that gradually abates. During the recovery process, physical therapy may or may not be needed.


Typical treatments include:

  • Rest and use of a sling until pain is reduced (up to four weeks)
  • Ice for pain and swelling


While surgical treatment is extremely rare, there are some instances when it might be performed including:

  • Persistent pain (greater that three months) over the AC joint area
  • Significant physical deformity – a large bump on the shoulder, particularly with thin people.
  • Gross instability of the joint (extremely rare)

Operative treatment can involve the removal of the AC joint, which can be performed with a minimally invasive arthroscopic technique. An alternative is a stabilization procedure conducted through a small one- to two-inch incision.

Recovery and Rehabilitation

Depending on the type of AC injury, patients usually heal with rest and non-operative therapy within two to three months. The range, dependent on grade, is usually two weeks for a Type I injury, six weeks for a Type II, and up to 12 weeks for a Type III.