AC Joint Injuries
What is an AC Joint Injuries?
The AC joint is short for the acromioclavicular joint. Separation of the two bones forming this joint is caused by damage to the ligaments connecting them. It is sometimes also referred to as a shoulder separation injury.
The acromioclavicular joint is formed by the outer end of the clavicle (collar bone) and the acromion process of the scapular (shoulder blade). The acromion is a bony process which protrudes forwards from the upper part of the scapular. This joint forms the highest part of the shoulder.
Grades of an AC Joint Injury
AC joint injuries are graded from 1-6 using the Rockwood scale which classifies injuries in relation to the extent of ligament damage and the space between the acromion and clavicle.
- Grade 1 is a simple sprain to the AC joint
- Grade 2 involves rupture of the AC ligament
- Grade 3 ruptures of both AC and CC ligaments which often results in a superior displacement.
From this point onwards the scale and grade of injury depends on the degree of displacement of the clavicle.
- Grade 4 involves posterior displacement
- Grade 5 superior displacement, to a greater degree than grade 3, with an increase incoracoclavicular space by 3-5 times the norm.
A step deformity may be apparent with grade 3, 4 & 5 injuries.
- Grade 6 involves full rupture of both AC and CC ligaments with the clavicle being displaced inferiorly.
How to treat an AC Joint Injury
- Rest and apply ice (cold therapy) in the early stage
- Immobilise the shoulder in a sling to ease pain by taking the weight of the arm
- Apply an AC joint separation taping which fixes and supports the joint into the correct position to assist with healing. You may need to be taped for 2-3 weeks
- Apply ultrasound for minor injuries, or TENS for pain relief in more severe cases
- Surgery if required (usually grades 4-6)
