ACJ pain & injuries

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The acromioclavicular joint (ACJ) is where your collarbone meets your shoulder blade. It enables you to make overhead movements and movements across your body with your arm. It is also used in pushing, pulling and lifting. The most common problems with the ACJ joint result from injuries, overuse or wear and tear.

A fall or direct impact can injure the ligaments of the ACJ, resulting in pain and loss of movement in your shoulder. ACJ injury is commonly referred to as shoulder separation, although the main ball and socket shoulder joint below may be unaffected.

ACJ pain:
ACJ pain can commonly occur with wear and degeneration (arthritis) of the joint itself or through overloading such as through excessive weights in the gym. This can cause pain felt particularly with overhead activities at the end of the collarbone. ACJ degeneration and pain can be more common with heavy overhead activities and work such as construction or plastering, and in younger patients from overloading such as through intensive and heavy weights in the gym. Physiotherapy exercises can help reduce pain. Steroid injections may also be an option and for cases that continue with pain despite other treatments, surgery may be required.

Causes of ACJ injuries

ACJ injuries may occur following a fall or heavy impact to the tip of the shoulder such as falling off a bicycle or colliding during a rugby tackle. It can also result from falling onto an outstretched arm, with the force of the impact being transmitted up through the arm. Heavy repetitive activities, such as weightlifting or throwing can injure the ACJ or cause pain due to osteolysis (thinning of the bone at the ACJ).

ACJ injury occurs most commonly in young men and women who are engaged in active sports.

Symptoms of ACJ injuries

ACJ injury can vary in severity from a mild strain to a complete ligament tear and deformity of the joint. Symptoms of ACJ injury include:

  • Pain at the top of the shoulder which may be accompanied by swelling, bruising or deformity of the ACJ.
  • A grating sound or sensation (crepitus), or clicking in the affected area.
  • Pain with overhead or across body movements.
  • Localised pain at night which may interfere with sleep.

Diagnosis of ACJ injuries

A physical examination and x-ray is used to diagnose ACJ injury. Occasionally further tests such as an MRI or ultrasound scan may be used to determine the extent of soft tissue damage and bruising.

Treatment of ACJ injuries

ACJ injuries are graded from one to five (grade six has been described but incredibly rare). Grade one and two injuries are normally treated by gently mobilising the arm and sometimes using a sling for comfort immediately after the injury. Painkillers, anti-inflammatories and an ice pack can be used to relieve pain and reduce swelling.

You may be referred to a physiotherapist who will be able to recommend exercises to improve mobility in the shoulder and strengthen the muscles.

If you have a more severe injury (grade three to five) you may require surgery to repair the damaged joint.


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