Injury to the anterior cruciate ligament during alpine skiing - A biomechanical analysis of tibial torque and knee flexion angle

Background: The anterior cruciate ligament has been shown to be particularly susceptible to injury during alpine skiing. Tibial torque is an important injury mechanism, especially when applied to a fully extended or fully flexed knee. Purpose: We wanted to record the forces generated in the anterior cruciate ligament with application of tibial torque to cadaveric knees in different positions. Study Design: Controlled laboratory study. Methods: Thirty-seven fresh-frozen cadaveric knees were instrumented with a tibial load cell that measured resultant force in the anterior cruciate ligament while internal and external tibial torques were applied to the tibia at full extension, 90degrees of flexion, full flexion, and forced hyperflexion. Results: At each knee flexion position, mean force generated by 10 N-m of internal tibial torque was significantly higher than the mean generated by 10 N-m of external tibial torque. Mean forces generated by tibial torque at 900 of flexion were relatively low. During flexion-extension without tibial torque applied mean forces were highest (193 N) when the knee was hyperflexed. Conclusions: Application of internal tibial torque to a fully extended or fully flexed knee represents the most dangerous loading condition for injury from twisting falls during skiing. Clinical Relevance: Understanding of the mechanisms of falls can be used to design better equipment and to better prevent or treat injury. (C) 2002 American Orthopaedic Society for Sports Medicine.