Differences in Quantitative Sensory Testing and Functional Testing Between Patients with Osteoarthritis and Matched Controls

Abstract

Background: Osteoarthritis (OA) is acknowledged as a complex, heterogeneous pathology. It has been suggested that new assessment approaches are needed to evaluate OA patients so that treatment can be targeted optimally. Objectives: This study aimed to investigate whether subjects with knee OA exhibit higher levels of sensory hyperalgesia and functional impairment, as measured using quantitative sensory test (QST) measures and standardised functional tests, than a cohort of healthy age and gender-matched controls. The relationship between quantitative tests and a self-report measure of quality of life was also investigated. Methods: 40 volunteers with painful knee OA were recruited in addition to 40 healthy volunteers, matched by gender and five-year age band (16 male: 24 female, mean age 64 years both groups). OA subjects were withdrawn from their usual analgesics / NSAIDs during testing. All subjects initially completed a SF36 Quality of Life questionnaire. Functional status was assessed using the aggregated locomotion function (ALF) score [1]: total time taken to complete three tasks – 3m chair transfer, 8m walk and a standardised flight of stairs. QST was applied at both knees and the unaffected right elbow with standard methods used and mean of 3 trials analysed. Cold and heat detection and pain thresholds (CDT, CPT, HDT, HPT) were tested using a peltier thermode (Medoc, Israel) and pressure pain thresholds (PPT) using a digital algometer (Somedic, AB).Results: There was a significant group difference in ALF score (p<.001 all tasks) with OA subjects performing the tasks on average 37% slower than controls. There was a significant group difference in CPT at all sites (p<.001) with OA subjects exhibiting a mean CPT of 11ºC (SD 7.8ºC) compared with controls (mean CPT 2.7ºC (SD 4.1ºC). PPT was reduced at all sites in OA patients, although only significantly at the OA knee (p=.003). There was no group difference in HPT or HDT at any site. In contrast, CDT was significantly less sensitive in the OA knee (p=.021) but not at other sites. SF36 scores showed no significant group difference in Mental Component (p=.961) although there was a significant difference in Physical Component (p=.048). Conclusions: When compared with age and gender-matched controls, subjects with knee OA demonstrated higher levels of cold and mechanical hyperalgesia which spread beyond the affected joint, associated with lower levels of physical function. QST and functional tests may therefore be useful tools with which to evaluate OA patients in the clinical setting and in clinical trials.