Biomedical Engineering, Northwestern University, Evanston, IL, USA; Shirley Ryan AbilityLab, Chicago, IL, USA.
Biomedical Engineering, Northwestern University, Evanston, IL, USA; Shirley Ryan AbilityLab, Chicago, IL, USA; Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, USA.
J Biomech. 2022 Oct;143:111282. doi: 10.1016/j.jbiomech.2022.111282. Epub 2022 Sep 5.
Ankle sprains are the most common musculoskeletal injury, typically resulting from excessive inversion of the ankle. One way to prevent excessive inversion and maintain ankle stability is to generate a stiffness that is sufficient to resist externally imposed rotations. Frontal-plane ankle stiffness increases as participants place more weight on their ankle, but whether this effect is due to muscle activation or axial loading of the ankle is unknown. Identifying whether and to what extent axial loading affects ankle stiffness is important in understanding what role the passive mechanics of the ankle joint play in maintaining its stability. The objective of this study was to determine the effect of passive axial load on frontal-plane ankle stiffness. We had subjects seated in a chair as an axial load was applied to the ankle ranging from 10% to 50% body weight. Small rotational perturbations were applied to the ankle in the frontal plane to estimate stiffness. We found a significant, linear, 3-fold increase in ankle stiffness with axial load from the range of 0% body weight to 50% body weight. This increase could not be due to muscle activity as we observed no significant axial-load-dependent change in any of the recorded muscle activations. These results demonstrate that axial loading is a significant contributor to maintaining frontal-plane ankle stability, and that disruptions to the mechanism mediating this sensitivity of stiffness to axial loading may result in pathological cases of ankle instability.
踝关节扭伤是最常见的肌肉骨骼损伤，通常是由于踝关节过度内翻引起的。一种预防过度内翻和维持踝关节稳定性的方法是产生足够的刚度以抵抗外部施加的旋转。随着参与者将更多的重量放在踝关节上，额状面踝关节刚度增加，但这种效应是由于肌肉激活还是踝关节的轴向加载尚不清楚。确定轴向加载是否以及在何种程度上影响踝关节刚度对于理解踝关节关节的被动力学在维持其稳定性中所起的作用非常重要。本研究的目的是确定被动轴向载荷对额状面踝关节刚度的影响。我们让受试者坐在椅子上，踝关节承受从体重的 10%到 50%的轴向载荷。在额状面施加小的旋转扰动以估计刚度。我们发现，从 0%体重到 50%体重的轴向载荷范围内，踝关节刚度呈显著的线性增加了 3 倍。这种增加不可能是由于肌肉活动引起的，因为我们没有观察到任何记录的肌肉激活有与轴向载荷相关的显著变化。这些结果表明，轴向加载是维持额状面踝关节稳定性的重要因素，而介导这种刚度对轴向加载敏感性的机制的中断可能导致病理性踝关节不稳定。
