Skier’s Thumb is caused by a traumatic force on the thumb that forces it out (thumb abduction and/or extension are the anatomical directions) damaging the ulnar collateral ligament at the metacarpophalangeal (MCP) joint . It often occurs with skiing and football.
Signs and symptoms include pain in the knuckle of the thumb, swelling, and an unstable joint. X-rays often show a small fragment of the metacarpal that has been pulled off by the ligament (called an avulsion fracture).
Treatment usually consists of bracing or splinting of partial tears and in some cases, surgical repair if the tear is complete.