Anterior cruciate ligament injuries in snowboarders: a quadriceps-induced injury.

Anterior cruciate ligament (ACL) injuries in snowboarders are rare. However, in expert boarders landing big jumps, ACL injuries are occurring more frequently. We identified 35 snowboarders with an identical injury mechanism. All these patients were landing from a jump. All described a flat landing on a flexed knee with significant knee compression. In 31 of 35 boarders, it was the front knee that was injured. Only two riders felt there was any twisting component to their injury. We postulate that the ACL rupture is due to maximal eccentric quadriceps contraction, as the boarder resists a compressive landing. Internal tibial rotation of the front knee in the snowboarding stance results in preloading of the ACL predisposing to injury.