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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

  • muscle tenderness of shoulder and collarbone,
  • swelling,
  • bruising,
  • limited mobility,
  • deformities i.e. a bump in the front or back of the shoulder
  • tenting of skin and
  • severe pain.

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
Certain risk factors can increase your risk of developing an AC Joint Injury, such as a dynamic lifestyle, active involvement in competitive sports activities and congenital/ acquired deformities of bone.

How MHC Treatment Options Can Help Condition

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Shoulder Recovery Program

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