Stig Heir, 1,2 Tron Krosshaug, 3 and Arne Ekeland 4 The Prevalence of Previous Serious Knee Injuries in Freestyle World Championship Skiers Reference: Heir, S., Krosshaug, T., and Ekeland, A., “The Prevalence of Previous Serious Knee Injuries in Freestyle World Championship Skiers”, Skiing Trauma and Safety: Fourteenth Volume, ASTM STP 1440, Robert J. Johnson, Ed., ASTM International, West Conshohocken, PA, 2003. Abstract: Previous major knee injuries among the participants in the FIS Freestyle World Championship 2001 in Whistler/Blackomb, Canada were recorded. Ninety-five skiers answered the questionnaire (response rate: 63%). Forty-seven percent of the skiers reported mean 1.6 previous serious knee injuries (range 1-5), female skiers with a significant higher prevalence than males. Thirty percent of the women and 24% of the men (p = 0.49) had suffered 1-3 ruptures of the anterior cruciate ligament (ACL) of the knee. There was no significant difference between the disciplines (mogul and aerial skiing) in the prevalence of any type of knee injury. In conclusion, nearly half of the responding FIS freestyle World Championship skiers had previously sustained one or more major knee injuries and still returned to such a high level of athletic performance. One fourth of the skiers had sustained one or more former ACL ruptures. The prevalence of previous serious knee injuries over all was significantly higher among female than among male skiers. Keywords: knee injuries, skiing injuries, skiing safety, prevalence, gender, freestyle, skiing, mogul skiing, aerials Freestyle skiing consists of mogul and aerial skiing. In freestyle mogul skiing the skier rides down a steep slope with irregular bumps (moguls) that are passed under time constraint. Mogul skiers exhibit a different pattern of muscle activation, a larger range of hip- and knee- angle movements, shorter time of movement cycles and higher hip and knee angular velocity than the traditional alpine racers [1]. In addition to the two required jumps, the skis are partly off the snow between the moguls, yielding repetitive __________________ 1 PhD student, Oslo Sport Trauma Research Center, Norwegian University of Sport & Physical Education, Box 4014 Ullevaal Stadion, N-0806 Oslo, Norway, E-mail: stighei@frisurf.no 2 Orthopaedic Surgeon, Martina Hansens Hospital, Box 23, N-1306 Baerum, Norway 3 PhD student, Oslo Sport Trauma Research Center, Norwegian University of Sport & Physical Education, Box 4014 Ullevaal Stadion, N-0806 Oslo, Norway 4 Director and Chief Surgeon, Martina Hansens Hospital, Box 23, N-1306 Baerum, Norway