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Acromioclavicular (AC) Joint Injury

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What Is an Acromioclavicular (AC) Joint Injury?

The acromioclavicular (AC) joint — along with ligaments — connects your collarbone and shoulder blade.

An injury to to the AC joint is a shoulder separation.

Types of AC joint injuries

The type of shoulder separation depends on how much you tear the AC joint or coracoclavicular (CC) ligaments that hold the joint in place.

  • Type I = the AC ligament is slightly torn, but there's no damage to the CC ligament is unharmed.
  • Type II = the AC ligament is completely torn, and there's little or no tear to the CC ligament.
  • Type III = both the AC and CC ligaments are completely torn. In this case, the collarbone separates from the end of the shoulder blade.

Three more types of AC joint injury are also possible, but rare. These involve tearing of the ligaments and surrounding muscle tissue.

Shoulder separation or AC joint injury causes

Shoulder separation often happens because of a hit to:

  • The tip of your shoulder.
  • The top part of your shoulder.
  • Your outstretched arm.

You may damage the AC joint or rotator cuff from a fall or tackle during a game.

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Acromioclavicular (AC) Joint Injury Symptoms and Diagnosis

AC joint injury symptoms

A shoulder separation may cause symptoms such as:

  • Pain
  • Limited motion in the shoulder
  • Swelling
  • Bruising
  • Tenderness at the top of the shoulder

You may also be able to see that the collarbone is out of place or notice a bump on the shoulder.

Testing for a shoulder separation or an AC injury

Your doctor will perform an exam to look for symptoms of an AC joint injury.

He or she will look at:

  • Blood flow
  • Muscle strength
  • Signs of a broken shoulder or damage to the rotator cuff

Your doctor will likely take an x-ray of the shoulder to see the severity of the damage and make sure you haven't fractured your collarbone.

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Acromioclavicular (AC) Joint Injury Treatment Goals and Options

The main goals of treatment for an AC joint injury are to manage pain and allow the torn ligaments to heal.

Type I or II AC joint injury treatment

Treatments for type I and II injuries include:

  • Icing the shoulder.
  • Putting your arm in a sling to decrease motion.
  • Taking NSAIDs, like ibuprofen or naproxen, to help with pain.

You will need to wear the sling for a few days to a week or more depending on how severe the injury.

You will need to begin physical therapy as soon as you can, and do minimal exercise with your arm to avoid frozen shoulder.

Type III AC joint injury treatment

Your doctor will decide the best course of treatment, based on the extent of damage to the joint.

You may have to wear a sling and undergo physical therapy.

In some cases, your doctor may suggest surgery to repair the torn ligaments.

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