Rheumatology：肥胖相关的炎症可能对膝OA患者的肌力存在影响

骨关节炎（OA）患者的炎性标志物，如C反应蛋白（CRP）和红细胞沉降率（ESR）通常仅出现轻度或中度升高。前期研究亦发现，升高的炎性标志物与患者的疼痛程度、整体病情严重度、功能受限之间存在相关性。然而炎性标志物与患者的肌力之间是否存在相关性，尚未被广泛研究。为明确这一问题，来自阿姆斯特丹康复研究中心的Diana C. Sanchez-Ramirez等人进行了一项研究。研究结果发表于2013年5月的《风湿病学》（Rheumatology）杂志上。研究发现，升高的血清CRP和ESR水平与较低的肌力之间存在相关性，但加入BMI这一变量后，则该相关性不再具有统计学意义。

该研究的横断面数据来源于阿姆斯特丹骨关节炎（AMS-OA）队列研究中的285例膝OA患者。从患者的血液样本中提取血清评估CRP（mg/l）和ESR（mm/l），检测结果在二分法后进行统计分析。股四头肌和腘伸肌群的肌力通过等动力肌力计进行测定。使用单变量和多变量线性回归分析法评估CRP和ESR与肌力间的相关性，同时对不同混杂因素进行统计调整。

通过对年龄、性别、合并症及应用NSAID药物等因素的调整后，研究发现升高的血清CRP水平（β=-0.10；p=0.04）和ESR水平（β=-0.12；p=0.02）与较低的肌力之间存在相关性。而在加入BMI这一变量后，该相关性不再有统计学意义。

研究者认为炎症可能对膝OA患者的肌力存在影响。炎症与肥胖之间的联系可以用于解释BMI对炎性标志物（如CRP和ESR）与肌力之间相关性的影响作用。

Association of serum C-reactive protein and erythrocyte sedimentation rate with muscle strength in patients with knee osteoarthritis.
OBJECTIVE
To examine the association of serum CRP and ESR with muscle strength in patients with knee OA.
METHODS
Cross-sectional data from 285 patients with knee OA from the Amsterdam Osteoarthritis (AMS-OA) cohort were analysed. CRP (mg/l) and ESR (mm/l) were measured in serum from patients' blood samples and the values were dichotomized for the analyses. Strength of quadriceps and hamstring muscles was assessed using an isokinetic dynamometer. Univariable and multivariable linear regression analyses were used to assess the association of CRP and ESR with muscle strength, adjusting for relevant confounders.
RESULTS
Elevated levels of serum CRP (β = -0.10; P = 0.04) and ESR (β = -0.12; P = 0.02) were associated with lower muscle strength after adjustment for age, sex, comorbidities and NSAID use. The associations were no longer significant when BMI was incorporated in the adjusted model.
CONCLUSION
Inflammation might influence muscle strength in patients with knee OA. Moreover, the link between inflammation and obesity might explain the effect that BMI has in the associations between inflammatory markers (i.e. CRP and ESR) and muscle strength.