AC Joint Injuries

Dr Marcus Chia - Shoulder Surgeon

Learn about AC joint injury causes and treatment options.

What are AC joint injuries?

AC joint injuries are injuries that occur on the AC (acromioclavicular) joint. The AC joint is formed between the end of the collarbone (clavicle) and a specific part (acromion) of the shoulder blade (scapula).

Your AC joint is the bony lump on top of your shoulder (that is covered by the bra strap in women). Its stability depends upon multiple ligaments and muscles.

AC joint injuries range from mild shoulder sprains to complete joint dislocations.

There are six types of AC joint injuries:

  • Type 1: swelling and tenderness but no visible deformity and normal X-rays
  • Type 2: slight widening of joint on X-rays
  • Type 3: complete dislocation of joint but with muscles still intact
  • Type 4: collarbone dislocated backwards
  • Type 5: muscles detached from end of collarbone and the collarbone can be felt just under the skin
  • Type 6: collarbone dislocated downwards (rare)

The type of injury depends on how the injury was caused and the amount of energy transferred to the joint.

What are the symptoms of AC joint injuries?

There are a range of AC joint injury symptoms which can vary, depending on the type of injury you have.

Common symptoms can include:

  • Pain, especially when lifting the arm or moving it across the body
  • Swelling
  • Deformity (a lump on top of the shoulder)
  • Bruising
  • Skin abrasions.

What causes AC joint injuries?

AC joint injuries are usually caused by a fall on the tip of the shoulder. This type of injury may damage the ligaments, muscles and cartilage in the joint. An AC joint injury can also fracture the collarbone or acromion.

Commonly, sporting injuries are the reason for a fall on the shoulder. Nearly half of all sporting shoulder injuries are AC joint injuries. Growth plate injuries in children and young adults can also cause AC joint injuries.

How do I know if I have an AC joint injury?

If you have recently had a fall on your shoulder and have symptoms of an AC joint injury, Dr Marcus Chia can examine your injury. A physical exam will assess the seriousness of the issue and rule out other potential injuries.

You will need an X-ray to diagnose the injury and determine which type of injury you have. In some cases, you may also need a CT or MRI scan.

What are the treatment options for AC joint injuries?

The treatment options for AC joint injuries include rest, strength exercises and rehabilitation, and surgery.

Non-surgical options

Most AC joint injuries can be treated without surgery. The first step of treatment is to control pain and swelling with ice and pain-relieving medications. You will need to rest your shoulder in a simple sling.

When your pain subsides, Dr Chia will develop a suitable rehabilitation program followed by strengthening exercises. You will need to avoid contact sports and heavy lifting for two to three months while you are healing.

If your injury is more severe, or if a rehabilitation program doesn’t heal your injury, you may need surgery.


Surgery will help to reduce the joint dislocation and stabilise the joint.

There are a range of surgical techniques for this type of surgery, and Dr Chia utilises key-hole surgery where possible. Key-hole surgery involves making a series of small cuts, rather than one large cut, to reconstruct the shoulder and achieve a faster recovery.

After surgery, you will need to place your shoulder in a sling for comfort. You can ice your injury to relieve pain and swelling. Dr Chia will give you a treatment plan which includes both active and passive exercises to increase your range of motion. You’ll need to avoid lifting any objects that weigh more than 2 kg, and you can start strengthening exercises three months after your surgery. You can return to sports and manual labour when your full range of motion and strength are back to normal.

Any surgical or invasive procedure carries risks. The information provided here is for general educational purposes only. For more information on AC joint injuries, or to learn more about arthroscopic AC joint repair, please contact the office of Dr Marcus Chia - Sydney Orthopaedic Shoulder and Elbow Surgeon.

For appointments and enquiries, please phone (02) 8014 4252

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Northern Beaches Hospital
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Frenchs Forest NSW 2086

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Wahroonga NSW 2076

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