Conditioned pain modulation as a predictor of central sensitization in primary knee osteoarthritis patients

Abstract

Aim of the workCentral sensitization (CS) is a nervous system disorder associated with chronic pain. This study aimed to quantify pain and evaluate conditioned pain modulation (CPM) and CS in knee osteoarthritis (KOA) patients with chronic pain. Patients and methodsThe study included 50 patients with primary KOA having chronic pain and 50 matched controls. The following assessment tools were used: visual analog scale (VAS)-pain, Western Ontario and McMaster Universities (WOMAC), pain DETECT questionnaire (PD-Q), and central sensitization inventory (CSI). Also, pressure pain threshold (PPT), electrical sensory threshold (EST), and electrical pain threshold (EPT) were assessed at both knees and remote sites. CPM was assessed using the submaximal effort tourniquet method, and the CPM ratio was measured (pre-to-post PPT). ResultsThe patients' mean age was 49.6 ± 9.7 years, 32 females and 18 males (F:M 1.2:1), and disease duration of 7.4 ± 3.6 years. Patients had a significantly higher CPM ratio (1.1 ± 0.21), PD-Q score (20.1 ± 9.1), CSI score (48.8 ± 21.4) compared to the control (0.9 ± 0.07; 8.3 ± 3.9 and 25.5 ± 9.4 respectively; p < 0.0001) and had a lower EPT and PPT in both knees and remote sites (p < 0.0001). CPM was significantly correlated with VAS-pain, WOMAC, CSI, PD-Q and inversely with EPT and PPT at both knees and remote sites and with EST at the right knee (p < 0.0001 each). CPM, PD-Q, and left knee EPT were significant predictors of CS tested with CSI (p < 0.0001, p < 0.0001, and p = 0.004, respectively). ConclusionThere is evidence of CS in KOA patients having chronic pain, and CPM and PD-Q can predict CS.