Knee biomechanics during a jump-cut maneuver: effects of sex and ACL surgery.

MIRANDA, D. L., P. D. FADALE, M. J. HULSTYN, R. M. SHALVOY, J. T. MACHAN, and B. C. FLEMING. Knee Biomechanics during a Jump-Cut Maneuver: Effects of Sex and ACL Surgery. Med. Sci. Sports Exerc., Vol. 45, No. 5, pp. 942-951, 2013. Purpose: The purpose of this study was to compare kinetic and knee kinematic measurements from male and female anterior cruciate ligament (ACL)-intact (ACL(INT)) and ACL-reconstructed (ACL(REC)) subjects during a jump-cut maneuver using biplanar videoradiography. Methods: Twenty subjects were recruited; 10 ACL(INT) (5 men and 5 women) and 10 ACLREC (4 men and 6 women, 5 yr postsurgery). Each subject performed a jump-cut maneuver by landing on a single leg and performing a 45 degrees side-step cut. Ground reaction force (GRF) was measured by a force plate and expressed relative to body weight. Six-degree-of-freedom knee kinematics were determined from a biplanar videoradiography system and an optical motion capture system. Results: ACL(INT) female subjects landed with a larger peak vertical GRF (P < 0.001) compared with ACL(INT) male subjects. ACL(INT) subjects landed with a larger peak vertical GRF (P <= 0.036) compared with ACL(REC) subjects. Regardless of ACL reconstruction status, female subjects underwent less knee flexion angle excursion (P = 0.002) and had an increased average rate of anterior tibial translation (0.05%.ms(-1) +/- 0.01%.ms(-1), P = 0.037) after contact compared with male subjects. Furthermore, ACL(REC) subjects had a lower rate of anterior tibial translation compared with ACL(INT) subjects (0.05%.ms(-1) T 0.01%.ms(-1), P = 0.035). Finally, no striking differences were observed in other knee motion parameters. Conclusion: Women permit a smaller amount of knee flexion angle excursion during a jump-cut maneuver, resulting in a larger peak vertical GRF and increased rate of anterior tibial translation. Notably, ACL(REC) subjects also perform the jump cut maneuver with lower GRF than ACL(INT) subjects 5 yr postsurgery. This study proposes a causal sequence whereby increased landing stiffness (larger peak vertical GRF combined with less knee flexion angle excursion) leads to an increased rate of anterior tibial translation while performing a jump-cut maneuver.