Effect of rearfoot strikes on the hip and knee rotational kinetic chain during the early phase of cuttings in female athletes

Purpose Biomechanical factors affecting horizontal-plane hip and knee kinetic-chain and anterior cruciate ligament (ACL) injury risks during cutting maneuvers remains unclear. This study aimed to examine whether different foot strike patterns alter horizontal-plane hip and knee kinetics and kinematics during a cutting maneuver in female athletes and clarify the individual force contribution for producing high-risk hip and knee loadings. Methods Twenty-five healthy female athletes performed a 60° cutting task with forefoot and rearfoot first strike conditions. Horizontal-plane hip and knee moment components, angles, and angular velocities were calculated using synchronized data of the marker positions on the body landmarks and ground reaction forces (GRF) during the task. The one-dimensional statistical parametric mapping paired t-test was used to identify the significant difference in kinetic and kinematic time-series data between foot strike conditions. Results In the rearfoot strike condition, large hip and knee internal rotation loadings were produced during the first 5% of stance due to the application of GRFs, causing a significantly larger hip internal rotation excursion than that of the forefoot strike condition. Dissimilarly, neither initial hip internal rotation displacement nor knee internal rotation GRF loadings were observed in the forefoot strike condition. Conclusion Rearfoot strike during cutting appears to increase noncontact ACL injury risks as the GRF tend to produce combined hip and knee internal rotation moments and the high-risk lower limb configuration. Conversely, forefoot strike during cutting appears to be an ACL-protecting strategy as the ACL-harmful joint loadings and lower-extremity configurations do not tend to be produced. Thus, improving foot strike patterns during cutting should be incorporated into ACL injury prevention programs.