Combined knee valgus and tibial internal rotation (VL + IR) moments have been shown to stress the anterior cruciate ligament (ACL) in several cadaveric studies. To utilize this knowledge for non-contact ACL injury prevention in sports, it is necessary to elucidate how the ground reaction force (GRF) acting point (center of pressure (CoP)) in the stance foot produces combined knee VL + IR moments in risky maneuvers, such as cuttings. However, the effects of the GRF acting point on the development of the combined knee VL + IR moment in cutting are still unknown. We first established the deterministic mechanical condition that the CoP position relative to the tibial rotational axis differentiates the GRF vector's directional probability for developing the combined knee VL + IR moment, and theoretically predicted that when the CoP is posterior to the tibial rotational axis, the GRF vector is more likely to produce the combined knee VL + IR moment than when the CoP is anterior to the tibial rotational axis. Then, we tested a stochastic aspect of our theory in a lab-controlled experiment. Fourteen females performed 60° cutting under forefoot/rearfoot strike conditions (10 trials each). The positions of lower limb markers and GRF data were measured, and the knee moment due to GRF vector was calculated. The trials were divided into anterior- and posterior-CoP groups depending on the CoP position relative to the tibial rotational axis at each 10 ms interval from 0 to 100 ms after foot strike, and the occurrence rate of the combined knee VL + IR moment was compared between trial groups. The posterior-CoP group showed significantly higher occurrence rates of the combined knee VL + IR moment (maximum of 82.8%) at every time point than those of the anterior-CoP trials, as theoretically predicted by the deterministic mechanical condition. The rearfoot strikes inducing the posterior CoP should be avoided to reduce the risk of non-contact ACL injury associated with the combined knee VL + IR stress.

中文翻译：

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女运动员切入动作早期地面反作用力作用点对膝外翻和胫骨内旋力矩的确定性条件

多项尸体研究表明，膝关节外翻和胫骨内旋 (VL + IR) 力矩的组合会对前十字韧带 (ACL) 造成压力。为了利用这些知识来预防运动中的非接触式 ACL 损伤，有必要阐明站立脚中的地面反作用力 (GRF) 作用点（压力中心 (CoP)）如何在危险情况下产生组合膝关节 VL + IR 力矩。动作，例如切割。然而，GRF 作用点对切削时膝关节 VL + IR 力矩发展的影响仍不清楚。我们首先建立了确定性力学条件，即 CoP 相对于胫骨旋转轴的位置区分了 GRF 矢量的方向概率，以产生组合膝关节 VL + IR 力矩，并从理论上预测，当 CoP 位于胫骨旋转轴后方时，GRF与 CoP 位于胫骨旋转轴前方时相比，矢量更有可能产生组合膝关节 VL + IR 力矩。然后，我们在实验室控制的实验中测试了我们理论的随机方面。 14 名女性在前脚/后脚着地条件下进行了 60° 切割（各 10 次试验）。测量下肢标记的位置和GRF数据，并计算GRF矢量引起的膝力矩。根据足部着地后 0 至 100 ms 之间每 10 ms 间隔的 CoP 相对于胫骨旋转轴的位置，将试验分为前 CoP 组和后 CoP 组，合并膝关节 VL + IR 力矩的发生率为试验组之间进行比较。正如确定性力学条件理论上预测的那样，后 CoP 组在每个时间点的膝关节 VL + IR 力矩组合的发生率（最大值为 82.8%）均显着高于前 CoP 试验。应避免后足撞击引起后 CoP，以降低与膝关节 VL + IR 联合应力相关的非接触性 ACL 损伤的风险。