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Subjects with Knee Osteoarthritis Exhibit Widespread Hyperalgesia to Pressure and Cold

Penny Moss*, Emma Knight and Anthony Wright

Hyperalgesia to mechanical and thermal stimuli are characteristics of a range of disorders such as tennis elbow, whiplash and fibromyalgia. This study evaluated the presence of mechanical and thermal hyperalgesia in individuals with knee osteoarthritis (OA), compared to healthy control subjects. Twenty-three subjects with knee OA and 23 healthy controls, matched for age, gender and BMI, were recruited for the study. Volunteers with any additional chronic pain conditions were excluded. Pain thresholds to pressure (PPT), cold (CPT) and heat (HPT) were tested at the knee, ipsilateral heel and elbow, in randomized order, using standardised methodology. Significant between-groups differences for PPT and CPT were found: OA subjects demonstrated significantly increased sensitivity to both pressure (p=0.018) and cold (p=0.003), but not to heat (p=0.167) stimuli, compared with controls. A similar pattern of results extended to the pain-free ipsilateral ankle and elbow indicating widespread pressure and cold hyperalgesia. This study found widespread elevated pain thresholds in subjects with painful knee OA, suggesting that altered nociceptive system processing may play a role in ongoing arthritic pain for some patients.