APPLIED SCIENCES Biodynamics Effect of Ski Binding Parameters on Knee Biomechanics: A Three-Dimensional Computational Study NANCY ST-ONGE 1 , YAN CHEVALIER 1 , NICOLA HAGEMEISTER 1,2 , MAXIME VAN DE PUTTE 1 , and JACQUES DE GUISE 1,2 1 Laboratory in Imaging and Orthopedic Research, Research Center of the University of Montreal Hospital Center, Notre- Dame Hospital, Montreal, CANADA; and 2 Ecole de Technologie Superieure (ETS), University of Quebec in Montreal (UQAM), Montreal, CANADA ABSTRACT ST-ONGE, N., Y. CHEVALIER, N. HAGEMEISTER, M. VAN DE PUTTE, and J. DE GUISE. Effect of Ski Binding Parameters on Knee Biomechanics: A Three-Dimensional Computational Study. Med. Sci. Sports Exerc., Vol. 36, No. 7, pp. 1218 –1225, 2004. Introduction: Downhill skiing is a relatively safe sport, but many potentially avoidable injuries do occur. Whereas tibia and ankle injuries have been declining, severe knee sprains usually involving the anterior cruciate ligament (ACL) have increased from the 1970s to the 1990s. The goal of the present study was to evaluate the effect of the position of the binding pivot point and binding release characteristics on ACL strain during a phantom-foot fall. Methods: We computed ACL strain using a biomechanical computer knee model to simulate the phantom-foot ACL-injury mechanism. This mechanism, which is one of the most common mechanisms of ACL injury in downhill skiing, occurs when the weight of the skier is on the inner edge of the ski during a backward fall, resulting in a sharp uncontrolled inward turn of the ski. Results: The model predicts, that under simulated phantom-foot conditions, a binding with fast-release characteristics with a pivot positioned in front of the center of the boot produces less strain on the ACL. Current bindings have their pivot point approximately at the center of the heel radius. A pivot positioned at the back of the binding is more effective for sensing loads that occur at the tip of the ski. However, it is less effective for sensing loads that occur at the tail of the ski and, therefore, offers less protection during a phantom-foot fall. Conclusion: A binding with two pivot points, one positioned in front and the other at the back, could sense twist loads applied to the ski both at the front and at the back, and might, therefore, be a solution to reduce the occurrence of ACL injuries. Key Words: SKI INJURY, PHANTOM-FOOT, ACL STRAIN, BINDING RELEASE CHARACTERISTICS, PIVOT POINT D ownhill skiing is a relatively safe sport. Neverthe- less, bindings allowing rigid fixation of the boot with the ski and long skis acting as levers through which forces can be transmitted to the lower extremity may expose skiers to many different types of lower-extremity injuries. The overall injury rate was estimated to be between 1 and 6 per 1000 skier-days in different studies from the 1970s to the 1990s (5,16,20,27,28). However, most authors agree that the incidence of injury has declined by approxi- mately 40 –50% over the years (5,17,18). Johnson et al. (17) observed that most of the decline in skiing injuries could be attributed to a 60% reduction in the incidence of lower-extremity injuries. In fact, lower-extrem- ity injuries, which account for 40 – 60% of all injuries (16,20), have been decreasing over the last 20 yr at Sugar- bush, Vermont (16 –18). Whereas tibia and ankle injuries have been decreasing by about 70 –90% (5,17), severe knee sprains usually involving the anterior cruciate ligament (ACL) have been increasing by as much as 170 –280% from the 1970s to the 1990s (5,17,18). In the late 1980s, ACL rupture was found to represent 2.4% of all injuries (20). However, from 1972 to 1994, grade-III sprain of the ACL was the most common injury in adult skiers, accounting for 18.4% of all injuries (5). According to J. E. Shealy (personal communication, 2002), the increase in ACL injuries oc- curred after the decline in tibial shaft fractures and is not related to binding system improvements that caused the Address for correspondence: Professor Jacques de Guise, LIO, Notre-Dame Hospital, Pav. J.A. de Seve, 1560 Sherbrooke East, Y-1614, Montreal (Quebec) Canada H2L 4M1; E-mail: jacques.deguise@etsmtl.ca. Submitted for publication April 2003. Accepted for publication February 2004. 0195-9131/04/3607-1218 MEDICINE & SCIENCE IN SPORTS & EXERCISE ® Copyright © 2004 by the American College of Sports Medicine DOI: 10.1249/01.MSS.0000132375.00721.7A 1218