The AC (acromioclavicular) joint is where the clavicle (collarbone) meets the acromion (shoulder blade).
Given its prominent position at the top of the shoulder, it is prone to being injured in a direct fall onto the tip of the shoulder. Such injuries are commonly seen in rugby players and mountain bike enthusiasts.
The collarbone is displaced upwards and the shoulder blade downwards.
AC joint injuries are classified according to the degree of displacement.
- Grade 1 – AC joint sprain
- Grade 2 – AC joint ligaments torn
- Grade 3 – AC joint 100% dislocated
- Grade 4 – Collarbone displaced backwards
- Grade 5 – AC joint 100% dislocated, with a markedly greater degree of separation than Grade 3
- Grade 6 – Collarbone displaced under coracoid
Treatment depends on the grade of the injury. Grades 1 and 2 AC joint dislocations are typically treated conservatively with painkillers and rest.
Grade 3 injuries may also be treated conservatively, although athletes and manual labourers would benefit from surgery.
Grades 4, 5 and 6 injuries require surgery with a number of options available to stabilise the joint. Your surgeon will discuss these with you.