Knee laxity, joint hypermobility, femoral anteversion, hamstring extensibility and navicular drop as risk factors for non-contact ACL injury in female athletes: A 4.5-year prospective cohort study

Purpose: To investigate whether six selected anatomical variables were associated with non-contact anterior cruciate ligament (ACL) injury in female team sport athletes. Methods: Two hundred eighty-seven female athletes (age 13–38 at baseline) from basketball, floorball, ice hockey and volleyball completed a baseline physical examination, including measurements of anterior-posterior (AP) knee laxity, knee hyperextension, generalized joint hypermobility, femoral anteversion, hamstring extensibility, and navicular drop. Athletes entered the study either in 2011, 2012 or 2013 and were followed up until the end of 2015. During the follow-up, all complete and magnetic resonance-verified ACL injuries were recorded. Results: Twenty-three non-contact ACL injuries were recorded. There were no significant differences in baseline physical examination variables between athletes who sustained ACL injuries and those who did not. However, a side-to-side difference in AP knee laxity greater than 2 mm was observed in 20% of the ACL injury group compared to 12% of the non-injured group, although this difference was not statistically significant. Conclusions: In this study, AP knee laxity, knee hyperextension, generalized joint hypermobility, femoral anteversion, hamstring extensibility and navicular drop were not associated with increased risk for non-contact ACL injury in female team sport athletes. This study was powered to detect moderate to strong risk associations; thus, smaller risk associations may not have been identified. Level of Evidence: Level II.