DescriptionThe interaction between gender, tibial rotation torque (direction), and valgus angle during a single-leg vertical jump-landing was examined (knee position). Subjects (N =30) were assessed during a one-time testing session. Peak torque and the ratio of peak torque to body weight for internal and external tibial rotation was obtained from the Biodex II dynamometer. Peak vertical ground reaction force was obtained from the Bertec force plate. Maximum vertical jump height, knee flexion angle, and knee varus/valgus angles were obtained from the MotionMonitor™ electromagnetic, 3-dimensional motion analysis system. A 2 x 2 (gender x direction) mixed factorial analysis of variance (ANOVA); 2 x 4 (gender x knee position) mixed factorial ANOVA; Pearson product moment correlation (torque and valgus); independent groups t-test between gender and the ratio of internal to external tibial rotation peak torque; and independent groups t-test between gender and the total valgus excursion during the jump-landing were computed. No significant interaction was found for gender x direction (p = .755) and/or gender x knee position (p =.555). Compared to males, females displayed an overall significantly (p = .016) greater valgus angle. Internal tibial rotation peak torque to body weight ratio was significantly (p = .001) less than external tibial rotation peak torque to body weight ratio. Subjects also displayed significantly (p = .001) greater knee valgus angle at initial contact and at peak valgus angle than at 3 0° of flexion and at peak vertical ground reaction force. No significant gender difference was found for the ratio of internal to external tibial rotation peak torque (p = .907) and/or the total valgus excursion during the jump-landing (p = .210).