Anterior cruciate ligament (ACL) injuries often occur during single limb landing or cutting. However, research studies investigating ACL biomechanics often analyze tasks involving both limbs. There are few studies that have examined the differences between knee kinematics during single and both limb tasks.
PURPOSE: To identify screening tests as well as the mechanism of ACL injury estimated by single and both limb athletic tasks.
METHODS: Twenty four female collegiate basketball and lacrosse athletes participated in this study. IRB approved informed consent was obtained from all subjects. The subjects performed both limb jump-landing, single limb landing and single limb plant-cutting tasks. The tasks were recorded using a high speed (200Hz) motion analysis system. Three dimensional knee motion analysis was used to calculate the differences in peak joint angle and angular joint excursion. ANOVA with repeated measures was performed to compare the differences between the tasks.
RESULTS: At the time of foot contact, the position of the knee was in varus rotation during all tasks and in external tibial rotation during single limb tasks. After foot contact, knee valgus and internal tibial rotation increased with time. The peak knee valgus angle was significantly larger in both limb jump-landing compared to single limb landing and plant-cutting (7.1±5.5, −1.2±5.3, −2.6±6.1, respectively; p<0.01). Excursion for internal tibial rotation was significantly larger in single limb landing and plant-cutting compared to both limb jump-landing (21.4±6.4, 26.8±6.8, 12.1±4.8, respectively; p<0.01).
CONCLUSION: The most likely mechanism of non-contact ACL injury is internal tibial rotation and valgus rotation of the knee. Both limb jump-landing is an appropriate screening test for knee valgus, however single limb tasks should be used for examining internal tibial rotation.