Shoulder instability is a common injury in athletes who participate in collision sport. Non-operative treatment has limited success and surgical treatment is frequently required. Rugby in particular is a high-risk collision sport for shoulder injury overall (instability 23% of total shoulder injuries). Tackle is recognised as the element of the game most conducive to the injury and a peak collision force of approximately 2000N is measured during a tackle. Instability injuries in collision athletes are the most severe. They have the highest rate of recurrence, resulting in the most days lost to injury, and have the largest negative effect on career length. Collision athletes with instability injuries will not be playing at full capacity, have a significant rate of re-injury, and have a high risk of injuring the other shoulder.