Gamekeeper's thumb results from disruption of the ulnar collateral ligament. Often associated with a fracture of the base of the proximal phalanx. Classically, a common injury in downhill skiing (thumb gets hung up in ski pole).
Stress views have been advocated if no fracture is identified on routine plain films but is clinically suspected. These views run the risk of displacing an undisplaced tear and creating a Stener lesion.