BACKGROUND Individuals with knee osteoarthritis (OA) demonstrate impairments in muscle function (i.e. muscle weakness, high muscle co-activation believed to have detrimental effects on joint integrity). Women with knee OA exhibit poorer health outcomes than men. Sex and muscle function are known risk factors for knee OA. It is unclear how these risk factors are associated with muscle function in knee OA and the implications for disease aetiology. RESEARCH QUESTION How does sex and knee osteoarthritis disease status relate to muscle function, specifically strength and muscle co-activation, during walking, stair negotiation and sit-to-walk activities. METHODS A cross-sectional study assessed muscle co-activation in 77 individuals with knee OA (mean[SD], 62.5[8.1] years; 48/29 women/men) and 18 age-matched controls (62.5[10.4] years; 9/9 women/men), during a series of walking, stair ascent and descent and sit-to-walk activities. Muscle strength of the knee extensors and flexors was assessed using maximal voluntary isometric contractions (MVIC). Electromyography was recorded from the vastus lateralis/medalis, rectus femoris, biceps femoris, semitendinosus, medial/lateral gastrocnemius normalised to MVIC. Multiple regression assessed the relationship between sex, disease status, and muscle strength on muscle co-activation. RESULTS Individuals with knee OA were weaker than controls, had higher hamstrings-quadriceps and medial-lateral co-activation for specific phases of gait. Women were weaker than men with higher muscle co-activation across all activities. Sex and muscle weakness, but not age or disease status predicted high muscle co-activation. SIGNIFICANCE High muscle co-activation was associated with female sex and muscle weakness regardless of disease status and age. High muscle co-activation is believed to be a compensatory mechanism for muscle weakness to maintain a certain level of function. High muscle co-activation is also thought to have detrimental effects on cartilage and joint integrity this may explain high muscle co-activation in women with muscle weakness and contribute to increased risk of incidence and progression of knee OA in women.

中文翻译：

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负重任务期间肌肉共激活中与性别和骨关节炎相关的差异。

背景技术患有膝骨关节炎（OA）的个体表现出肌肉功能受损（即，肌肉无力，高肌肉共同激活被认为对关节完整性具有有害影响）。膝骨关节炎女性的健康状况较男性差。性别和肌肉功能是膝盖骨关节炎的已知危险因素。目前尚不清楚这些危险因素与膝骨关节炎的肌肉功能如何相关以及对疾病病因的影响。研究问题性，膝关节骨关节炎疾病状态与行走，楼梯谈判和坐坐活动期间的肌肉功能，特别是力量和肌肉共同激活有何关系。方法一项横断面研究评估了77例膝OA患者的肌肉共激活（平均[SD]，62.5 [8.1]岁； 48/29妇女/男人）和18个年龄匹配的对照组（62.5 [10.4]岁； 9）。 / 9位女性/男性），在一系列步行，楼梯上升和下降以及坐着步行活动中。使用最大自愿等距收缩（MVIC）评估膝伸肌和屈肌的肌力。从MVIC标准化后的肌外外侧/内脏，股直肌，股二头肌，半腱肌，内侧/外侧腓肠肌记录肌电图。多元回归评估了性别，疾病状态和肌肉共同激活时肌肉力量之间的关系。结果膝OA的个体比对照组弱，对于特定步态阶段具有较高的绳肌-股四头肌和内侧-外侧共激活。在所有活动中，女性均比具有较高肌肉共同激活能力的男性弱。性别和肌肉无力，但年龄或疾病状况却不能预测高肌肉共激活。重要性高肌共激活与女性和肌肉无力相关，与疾病状态和年龄无关。高肌肉共激活被认为是肌肉无力维持某种功能水平的一种补偿机制。人们还认为，高强度的肌肉共同激活会对软骨和关节的完整性产生不利影响，这可以解释患有肌肉无力的女性的较高肌肉的共同激活，并增加女性膝盖OA发生和发展的风险。