Knee valgus during landing has been identified as a strong correlate of ACL injury. Inappropriate trunk control during landing contributes to high knee valgus, with neuromuscular factors related to core stability postulated as the mechanism. This investigation probed the influence of trunk and hip mechanics, including joint stiffness, on knee mechanics, particularly high knee valgus. Specifically, this study quantified lumbar spine and hip joint rotational stiffness (a proxy for mechanical joint stability) during single-leg landing tasks known to be associated with injury risk, particularly in females. Kinematics, kinetics, and 24 channels of electromyography spanning the trunk and hip musculature were measured in 18 healthy female participants. Anatomically detailed EMG-driven musculoskeletal models quantified lumbar spine and hip joint rotational stiffness. The links between peak knee abduction angle and moment with lumbar spine and hip joint rotational stiffness were measured. Hip joint rotational stiffness influenced knee abduction across tasks (correlation coefficient ranging from -0.48 to -0.70, p<0.05) to reduce valgus deviation. Similarly, transverse plane hip joint rotational stiffness during landings reduced knee abduction moment (R = -0.50, P=0.03; R = -0.49, P=0.04), and lumbar spine joint rotational stiffness reduced knee abduction angle and moment but did not consistently reach statistical significance. The control system uses stiffness to control motion. This study demonstrates the importance of proximal (lumbar spine and hip) joint rotational stiffness (i.e. core control stability) during single-leg landing to prevent knee abduction motion. Instantaneous core stability is achieved with the coordinated activation and stiffness of both trunk and hip muscles.

着陆过程中的膝外翻被认为与ACL损伤密切相关。着陆时躯干控制不当会导致高膝外翻，其机制可能与与核心稳定性有关的神经肌肉因素有关。这项研究探讨了躯干和髋部力学（包括关节僵硬）对膝关节力学的影响，尤其是高膝外翻。具体而言，这项研究量化了单腿着陆任务期间腰椎和髋关节的旋转僵硬度（代表机械关节稳定性），已知与受伤风险有关，尤其是女性。在18名健康女性参与者中测量了运动，动力学和横跨躯干和髋部肌肉组织的24个肌电图通道。解剖学详细的肌电图驱动的肌肉骨骼模型量化了腰椎和髋关节的旋转刚度。测量了峰值膝关节外展角和腰椎弯矩与髋关节旋转刚度之间的联系。髋关节旋转刚度影响跨任务的膝关节外展（相关系数范围从-0.48到-0.70，p <0.05），以减少外翻偏差。同样，着陆时髋关节横向平面的旋转刚度降低了膝盖的外展力矩（R = -0.50，P = 0.03; R = -0.49，P = 0.04），并且腰椎关节旋转刚度降低了膝关节外展角度和力矩，但未始终达到统计学意义。控制系统使用刚度来控制运动。这项研究证明了单腿着陆期间近端（腰椎和臀部）关节旋转刚度（即核心控制稳定性）的重要性，以防止膝盖外展运动。躯干和髋部肌肉的协调激活和刚度可实现瞬时核心稳定性。