A comparison of two wind-up methodologies in patients with osteoarthritis vs normal controls

This study explored the effectiveness of producing the thermal wind-up phenomenon comparing two methodologies. Participants included 37 subjects with osteoarthritis of the knee and 35 controls matched as to age, sex, and race. The study was conducted during a single session which included psychometric testing, history and physical, and psychophysical testing (quantitative sensory testing [QST] and wind-up). All testing was conducted at three sites; the medial and lateral joint lines of the most painful knee, and the elbow contralateral to the most painful knee. Participants received one of two wind-up procedures: windup temperatures determined by averages of heat pain threshold temperatures obtained during QST (range = 44.0° – 49.7° Celsius) or at a single super-threshold temperature of 49°. All participants received three trains of 5 heat ‘taps' at each location. The three trains were averaged and slopes were subsequently calculated for each location. Slopes were used to represent the magnitude of the windup effect. A 2x2x3 (participants x windup methodology x location) mixed-model repeated measures ANOVA was used to analyze the data. Location served as the within subjects factor and participants and methodology were the between subjects factors. Windup did not differ significantly by location (F = 2.850, p =.075). OA participants produced significantly greater mean windup slopes than did the control participants (F = 10.340, p =.002) and the super-threshold windup procedure yielded significantly greater mean slopes compared to the pain threshold windup procedure (F = 9.189, p = .004). There was a significant participant by windup methodology effect (F = 6.202, p = .015). There was a greater magnitude of windup in the OA participants, especially when using the super-threshold temperature. The implications of these finding to pain research will be discussed. This study was supported by a grant from GlaxoSmithKline.