KNEE Differences in ACL biomechanical risk factors between field hockey and lacrosse female athletes Hillary J. Braun • Rebecca Shultz • Maria Malone • Whitney E. Leatherwood • Amy Silder • Jason L. Dragoo Received: 4 March 2013 / Accepted: 23 January 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract Purpose Previous investigations have revealed a greater incidence of anterior cruciate ligament (ACL) injuries in female lacrosse versus field hockey players. Lacrosse is played in an upright posture with overhead throwing and catching, while field hockey is almost exclusively played in a crouched, forward-flexed position. Biomechanical fac- tors, including decreased knee, hip, and trunk flexion angles, have been identified as risk factors for ACL injury. The purpose of this study was to assess ACL biomechan- ical risk factors in female field hockey and lacrosse players to determine whether sport-specific posture might con- tribute to the increased incidence of ACL injury observed in lacrosse athletes. Methods Thirty-one Division I NCAA females from field hockey and lacrosse completed four tasks, three times per leg: bilateral drop jump, single-leg drop jump (SDJ), sin- gle-leg jump onto a Bosu ball (SDB), and a 45° anticipated cut. Kinematic and force plate data were used to evaluate knee flexion angle, knee adduction moment, hip flexion angle, and trunk flexion and sway angles. Muscle activity of the lateral hamstrings and vastus lateralis was used to estimate peak hamstring activity and the quadriceps/ham- string ratio at the time of peak quadriceps activity (co- contraction ratio). Results During the SDJ and SDB, peak knee flexion angles were greater in field hockey compared with lacrosse. During cutting, field hockey players were more flexed at the trunk and had greater trunk sway, compared with the lacrosse players. No significant difference was observed for the co-contraction ratio for any of the tasks. Conclusions Decreased knee flexion angle during land- ing, consistent with sport-specific playing postures, may contribute to the higher incidence of ACL injury in lacrosse players relative to field hockey. Sport-specific training injury prevention programmes may benefit from consider- ing these differences between specialized athletes. Level of evidence II. Keywords ACL Á Biomechanics Á Knee flexion Á Female sports Á Lacrosse Á Field hockey Introduction Field hockey and lacrosse are two female sports that require running, cutting, and the manipulation of a ball and stick; however, their lower extremity mechanics differ substantially. In field hockey, the ball is handled and pas- sed on the ground, which requires players to assume a crouched position with high degrees of both trunk and knee flexion, while in lacrosse the ball is cradled and passed with overhead throwing and catching movements, which tend to occur with less knee flexion. H. J. Braun Á R. Shultz Á M. Malone Á W. E. Leatherwood Á A. Silder Á J. L. Dragoo Department of Orthopaedic Surgery, Stanford University, Palo Alto, CA, USA H. J. Braun School of Medicine, University of California San Francisco, San Francisco, CA, USA A. Silder Department of Bioengineering, Stanford University, Palo Alto, CA, USA J. L. Dragoo (&) Department of Orthopaedic Surgery, Stanford University, 450 Broadway Street, Pavilion C, 4th Floor, Redwood City, CA 94063-6342, USA e-mail: jdragoo@stanford.edu 123 Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-014-2873-0