AC Joint Injury
AC Joint Injury, also known as Acromioclavicular (AC) Joint Injury, AC Joint Separation or Shoulder Separation, occurs when ligaments between the collarbone are injured or torn.
What is AC Joint Injury?
The pathophysiology of an injury to the Acromioclavicular ligaments or joint involves either of the four mechanisms:
- Tearing of trapezoid and conoid ligaments
- Tearing of acromioclavicular ligaments
- Upward movement of lateral clavicle
- Avulsion of trapezoid-conoid ligaments
The degree of separation of an AC Joint Injury can categorized in stages:
- Stage 1 – a mild AC Joint injury involving a sprain to the AC ligament that does not move the collarbone
- Stage 2 – AC ligament is torn and the coracoclavicular (CC) ligament is sprained or slightly torn; the collarbone will be out of alignment to a slight extent, showing a small bump
- Stage 3 – Most severe AC Joint injury. AC and CC ligaments are completely torn, and collarbone is noticeably out of position, with a large bump

AC Joint Injury, showing AC and CC ligament tear
Signs and Symptoms of AC Joint Injury
AC Joint Injury presents with
Causes of AC Joint Injury
In about 65% of the cases, the injury process is the result of active involvement in competitive sports (such as football, volley ball, ice hockey etc.). Other causes of AC Joint Injury include;
- history of fall on a hard surface that compromises the muscular or nervous elements or
- assault eg being hit in the shoulder or
- trying to break a fall with your hand
How MHC Treatment Options Can Help Condition
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Shoulder Recovery Program
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