Ulnar collateral ligament injury of the thumb

Gamekeeper's thumb (also known as skier's thumb or UCL tear) is a type of injury to the ulnar collateral ligament (UCL) of the thumb. The UCL may be merely stretched, or it may be torn from its insertion site into the proximal phalanx of the thumb; in approximately 90% of cases part of the bone is actually avulsed (sheared away) from the joint. This condition is commonly observed among gamekeepers and Scottish fowl hunters, as well as athletes (such as volleyballers and soccer goalkeepers). It also occurs among people who sustain a fall onto an outstretched hand while holding a rod, frequently skiers grasping ski poles.