Effect of the foot-strike pattern on the sagittal plane knee kinetics and kinematics during the early phase of cutting movements

Abstract

Anterior cruciate ligament (ACL) injury occurs soon after foot-strike. Cutting with a shallow flexed knee is considered a risk factor for ACL injury; however, how foot-strike patterns (forefoot strike [FFS] vs. rearfoot strike [RFS]) affect sagittal plane knee kinetics and kinematics after a foot-strike, is unknown. This study aimed to investigate the effect of foot-strike patterns on the sagittal plane knee kinetics and kinematics during cutting. Twenty-three males performed 45° cutting under RFS and FFS conditions. The marker position data on the lower limb, and the ground reaction force (GRF) data were collected and time-normalized (0–100%) during the stance phase. The knee flexion angle, shank and GRF vector inclination angle relative to the global vertical axis, knee flexion/extension moment, and anterior/posterior component of GRF relative to the shank segment were calculated and compared between foot-strike patterns using statistical parametric mapping paired t-test (p < 0.0071). The knee flexion angle was smaller in RFS than in FFS in the initial 40% of the stance phase. In the RFS condition, the GRF vector was directed anteriorly to the shank segment, and the knee extension moment was produced by GRF in 0–7% of the stance phase, while these results were not observed in the FFS condition. These results suggest that compared to FFS, RFS induces a shallow flexed knee with an anterior-directed GRF component in the early stance phase and might potentially provoke a risk of ACL injury.