Jørgensen Tanja Schjødt, Henriksen Marius, Rosager Sara, Klokker Louise, Ellegaard Karen, Danneskiold-Samsøe Bente, Bliddal Henning, Graven-Nielsen Thomas
Clinical Motor Function Laboratory, The Parker Institute, Department of Rheumatology, Copenhagen University Hospital, Bispebjerg and Frederiksberg, Denmark.
Laboratory for Musculoskeletal Pain and Motor Control, Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg Denmark.
Scand J Pain. 2015 Jan 1;6(1):43-49. doi: 10.1016/j.sjpain.2014.11.002.
Background and aims Despite the high prevalence of knee osteoarthritis (OA) it remains one of the most frequent knee disorders without a cure. Pain and disability are prominent clinical features of knee OA. Knee OA pain is typically localized but can also be referred to the thigh or lower leg. Widespread hyperalgesia has been found in knee OA patients. In addition, patients with hyperalgesia in the OA knee joint show increased pain summation scores upon repetitive stimulation of the OA knee suggesting the involvement of facilitated central mechanisms in knee OA. The dynamics of the pain system (i.e., the adaptive responses to pain) has been widely studied, but mainly from experiments on healthy subjects, whereas less is known about the dynamics of the pain system in chronic pain patients, where the pain system has been activated for a long time. The aim of this study was to assess the dynamics of the nociceptive system quantitatively in knee osteoarthritis (OA) patients before and after induction of experimental knee pain. Methods Ten knee osteoarthritis (OA) patients participated in this randomized crossover trial. Each subject was tested on two days separated by 1 week. The most affected knee was exposed to experimental pain or control, in a randomized sequence, by injection of hypertonic saline into the infrapatellar fat pad and a control injection of isotonic saline. Pain areas were assessed by drawings on anatomical maps. Pressure pain thresholds (PPT) at the knee, thigh, lower leg, and arm were assessed before, during, and after the experimental pain and control conditions. Likewise, temporal summation of pressure pain on the knee, thigh and lower leg muscles was assessed. Results Experimental knee pain decreased the PPTs at the knee (P <0.01) and facilitated the temporal summation on the knee and adjacent muscles (P < 0.05). No significant difference was found at the control site (the contralateral arm) (P =0.77). Further, the experimental knee pain revealed overall higher VAS scores (facilitated temporal summation of pain) at the knee (P < 0.003) and adjacent muscles (P < 0.0001) compared with the control condition. The experimental knee pain areas were larger compared with the OA knee pain areas before the injection. Conclusions Acute experimental knee pain induced in patients with knee OA caused hyperalgesia and facilitated temporal summation of pain at the knee and surrounding muscles, illustrating that the pain system in individuals with knee OA can be affected even after many years of nociceptive input. This study indicates that the adaptability in the pain system is intact in patients with knee OA, which opens for opportunities to prevent development of centralized pain syndromes.
背景与目的 尽管膝关节骨关节炎（OA）的患病率很高，但它仍是最常见的无法治愈的膝关节疾病之一。疼痛和功能障碍是膝关节OA的突出临床特征。膝关节OA疼痛通常局限于局部，但也可能放射至大腿或小腿。在膝关节OA患者中发现了广泛的痛觉过敏。此外，膝关节OA关节存在痛觉过敏的患者在对OA膝关节进行重复刺激时，疼痛总和评分增加，这表明中枢机制的易化参与了膝关节OA。疼痛系统的动态变化（即对疼痛的适应性反应）已得到广泛研究，但主要是基于对健康受试者的实验，而对于慢性疼痛患者疼痛系统的动态变化了解较少，因为在慢性疼痛患者中，疼痛系统已被激活很长时间。本研究的目的是在实验性膝关节疼痛诱发前后，对膝关节骨关节炎（OA）患者的伤害感受系统动态变化进行定量评估。方法 10名膝关节骨关节炎（OA）患者参与了这项随机交叉试验。每个受试者在相隔1周的两天进行测试。通过向髌下脂肪垫注射高渗盐水和对照注射等渗盐水，以随机顺序使受影响最严重的膝关节接受实验性疼痛或对照处理。通过在解剖图上绘图来评估疼痛区域。在实验性疼痛和对照处理之前、期间和之后，评估膝关节、大腿、小腿和手臂的压痛阈值（PPT）。同样，评估膝关节、大腿和小腿肌肉上压力疼痛的时间总和。结果 实验性膝关节疼痛降低了膝关节的PPT（P<0.01），并促进了膝关节及相邻肌肉的时间总和（P<0.05）。在对照部位（对侧手臂）未发现显著差异（P = 0.77）。此外，与对照处理相比，实验性膝关节疼痛在膝关节（P<0.003）和相邻肌肉（P<0.0001）处显示出总体更高的视觉模拟评分（疼痛时间总和易化）。与注射前的OA膝关节疼痛区域相比，实验性膝关节疼痛区域更大。结论 在膝关节OA患者中诱发的急性实验性膝关节疼痛导致痛觉过敏，并促进了膝关节及周围肌肉的疼痛时间总和，说明即使经过多年的伤害性输入，膝关节OA患者的疼痛系统仍会受到影响。本研究表明膝关节OA患者疼痛系统的适应性是完整的，这为预防中枢性疼痛综合征的发展提供了机会。
