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Acromioclavicular joint injuries (AC)

The Acromioclavicular or A/C joint sits on the point of the shoulder, above the main joint of the shoulder (which is called the glenohumeral joint). The A/C joint plays a role in the biomechanics of throwing and other upper-limb activities. A/C joint injuries occur from falling directly on the point of the shoulder or from a direct clash of shoulders between players.

A/C joint injuries are graded in severity from 1-6 although usually only Grades 1-3 are seen in sporting injuries. A Grade 3 represents a total joint separation while Grade 1-2 injuries usually settle in a matter of weeks without requiring surgery. Professional football players will often be injected with local anaesthetic to play with a Grade 1-2 A/C joint.

To read more about this process, see the following article from the British Journal of Sports Medicine Benefits and risks of using local anaesthetic for pain relief to allow early return to play in professional football [PDF].

Grade 3 or 3+ injuries to the A/C joint sometimes require surgery (which can keep a professional player out for 6-8 weeks) although some players may be able to return after a few weeks without surgery.
Kane Cornes AC Joint injury
Kane Cornes of Port Adelaide injured his AC joint during a loss to North Melbourne in 2009.
(Image sourced from afl.com.au)
AC joint injury
AC Joint injury in an NRL Sydney Roosters player