Muscle fatigue affects dynamic tibiofemoral movements during jumping tasks in healthy participants

Purpose The main function of the anterior cruciate ligament (ACL) is to restrain anterior tibia translation (ATT) and internal tibia rotation (ITR) relative to the femur. Muscle fatigue has been identified as a potential risk factor for ACL injury due to its negative effects on neuromuscular control, proprioception, and joint stability. The aim of this study was to determine the influence of muscle fatigue on dynamic ATT (ATTd) and dynamic ITR (ITRd) during the single‐leg hop for distance (SLHD) and side hop (SH) in healthy participants. Methods Twenty healthy participants were included. ATTd, ITRd and knee flexion angle were assessed during the SLHD and SH using a 3D motion capture system in a nonfatigued and fatigued condition. Fatigue was induced by 30 s of squat jumps before each task. ATTd, ITRd and knee flexion angle were analysed using statistical parametric mapping (SPM) to compare conditions, from initial contact (IC) to 0.75 s after IC. Results During the fatigued condition, a significant increase in ATTd was observed for both the SLHD ( p = 0.002; 0.06–0.38 s after IC) and the SH ( p = 0.02; 0.15–0.36 s after IC). No significant differences were observed in ITRd during both tasks. A significant increase in knee flexion angle was observed during the fatigued condition for the SH ( p = 0.048; 0.11–0.15 s after IC), but not for the SLHD. Conclusion Muscle fatigue resulted in increased ATTd, offering new insights into intra‐articular knee kinematics in fatigued conditions. The observed changes were not multiplanar and did not match timing typically associated with ACL injury mechanisms, leaving the relevance to injury risk unclear. Level of Evidence Level II.