Until you asked, this physician always figured it was the hand signal used by skiers hitchhiking to and from their down-valley hovels. Turns out, skier's thumb is an injury of the ulnar collateral ligament—the one on the inner side of the digit that holds the bones together at the metacarpophalangeal joint. It accounts for 8 to 10 percent of all skiing injuries, and for good reason: When you fall with a ski pole in your grip, the implement acts as a fulcrum that can cause the ligament to stretch or tear. Should this happen, you'll suffer pain at the base of the thumb, topped off by swelling, black-and-blue discoloration, and weakness of grasp. If you tear the ligament completely, plan on surgery and four months' rehab. Partial tears can require four to six weeks of immobilization in a cast. Interestingly, skier's thumb was—and still could be, for all we know—a chronic ailment among Scottish gamekeepers, who thrashed their digits by repeatedly wrenching the necks of hares. Later, the ski boom served up many more such cases—hence, "skier's thumb. But Flake hopes the medical establishment will rethink the injury's nomenclature and offically name it, "Scots-who-twist-the-heads-off-too-many-rabbits' thumb.