The relationship between neuropathic pain symptoms on the modified pain detect and signs of central sensitization in knee osteoarthritis

Abstract

Purpose: Central sensitization may contribute to pain in a subset of people with knee OA and present with a distinct clinical phenotype including neuropathic-like symptoms and sensory abnormalities. A neuropathic pain (NP) questionnaire modified for use in knee OA, the modified painDETECT (mPD-Q), may aid the identification of central sensitization in this population. The aim of this novel study was to assess the relationship between mPD-Q scores and signs of central sensitization, assessed using a quantitative sensory testing (QST) protocol, in adults with chronic knee OA. Methods: Eligible participants had chronic, symptomatic, knee OA, without other pain or neurological conditions. Age and gender matched reference data was obtained from controls, enabling identification of sensory abnormalities among individual participants. Prior to QST, data was collected on NP symptoms (mPD-Q) for each knee, sociodemographic factors, BMI, OA duration and severity (WOMAC), pain intensity (Von Korff Chronic Pain Grade, CPG, pain intensity subscale), depressive symptoms (Centre for Epidemiologic Studies Depression Scale, CES-D), and pain catastrophizing (pain catastrophizing scale, PCS). The standardized/ comprehensive QST protocol, developed by the German Research Network on Neuropathic Pain (DFNS), was conducted on the medial aspect of all eligible knees. QST signs of central sensitization were defined as: mechanical hyperalgesia and/or enhanced temporal summation and /or allodynia. Abnormal sensation was defined as QST findings >2 standard deviations above or below the mean of controls. Generalized estimating equation modeling was used to examine the relationship between the presence of central sensitization (yes/no) and mPD-Q scores (above or below the median) by knees. Results: The majority of the 36 participants were female (83.3%) and Caucasian (83.3%), aged (SD) 60.7 (6.8) years, with a high median (min, max) BMI of 28.2 (19.5, 62.3). Mean (SD) duration of knee symptoms and time since knee OA diagnosis were 13.6 (13.2) years and 7.4 (10.0) years, respectively. Mean (SD) severity of OA was moderate: WOMAC total was 38.7/96 (18.5), CPG score was 52.0/100 (19.8). Among the 36 study participants, 57 knees were painful and eligible for participation. Median mPD-Q score among all knees was 9 (range 0-33). 45.6% of assessed knees had ± 1 sign of central sensitization in order of frequency: mechanical hyperalgesia (36.8%), enhanced temporal summation (10.5%), and allodynia (5.3%). Controlling for age, individuals with higher mPD-Q scores (± the median of 9.0) had a significantly higher odds of meeting our criteria for central sensitization (adjusted OR = 3.85; 95% CI, 1.16-12.7, p =0.027). Additional adjustment for pain catastrophizing, pain intensity, or depressed mood did not attenuate this relationship. Conclusions: Among a sample of adults with chronic, painful knee OA, higher scores on the mPD-Q were associated with greater odds of having one or more sign of central sensitization on QST. Thus, the mPD-Q may aid the identification of central sensitization in adults with chronic knee OA.