THE INJURY
A dislocated shoulder is common in contact sports such as rugby union or rugby
league. The shoulder is a ball-and-socket joint that has a large range of
movement but not a lot of stability. It is particularly unstable when it is rotated
outwards and the arm cocked back or 'abducted'. Any additional force in this
position will cause the head of the humerus (arm) bone to come out of the joint
in a forward direction. This is referred to as an anterior dislocation.
The shoulder joint is enclosed by a fibrous capsule, and this is strengthened by
ligaments that provide a reinforced thickening of the capsule. The joint also has a
'labrum', which is a fibrocartilage lip that increases the congruency of the joint. In
the case of a traumatic dislocation, the joint capsule and ligaments are torn, and
the labrum may also be damaged.
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PREVENTION
Once there has been a dislocation of the shoulder, the joint will have a degree of
instability and will be more likely to dislocate again, or become subluxed (where it
moves slightly but not fully out of joint). This is because the ligaments, capsule
and labrum are damaged and cannot restrain the humeral head and prevent
dislocation. In order to prevent dislocation, the muscles that surround the
humeral head should be strengthened.