Exploratory evaluation of a treadmill walking model to assess treatment-related analgesia in subjects with osteoarthritis knee pain

Abstract

8pm). To characterize the statistical properties of the time series of pain ratings, the means of the pain ratings in three blocks were calculated and compared by one way analysis of covariance. As well, fractal dimension, D, was calculated using rescaled range analysis to characterize the OA participants' pain fluctuations. Results: Thirty-two individuals participated in the study (18 females, age (mean, standard deviation) 59.7 AE6.5 yr; 10 males, 55.3AE6.7 yr). As shown in Figure A, there is no significant difference among the three blocks of time for the mean rating of pain. Figure B displays the distribution of fractal dimension, D. calculated for each individual's mean daily pain intensity. The mean fractal dimension, D, for the population is 1.65AE0.04, which signifies an anti-persistent pain time series. Conclusions: This is the first analysis to characterize the fractal dimension of OA pain. The finding of anti-persistent time series means that on average more intense pain is followed by lesser pain, a finding very similar to that reported for chronic low back pain and in contrast to both purely neuropathic pain and acute pain. Whereas these previous studies were over short time periods, this study suggests that power law scaling can be preserved for much longer periods of time (weeks or months), which is significant for clinical application. The anti-persistent pattern of pain is consistent with the concept of central pain processes activated to modulate peripheral pain input in OA.