Neuropathic pain in patients with primary knee osteoarthritis: A cross-sectional study.

Introduction: Neuropathic pain (NP) is believed to be a distinct subtype of pain associated with knee osteoarthritis (KO). This study aimed to determine the prevalence of NP in patients with primary KO and examine its correlation with various factors.

Methods: A cross-sectional study was conducted on 195 patients with primary KO who did not have the following conditions: knee surgery, infection, rheumatic diseases, peripheral and central neurological diseases, patients who received treatment for neuropathic pain in the past 6 months, diabetes, renal failure, and alcoholism. NP was evaluated using two standardized questionnaires, the Douleur Neuropathique 4 questions (DN4) and the painDETECT questionnaire.

Results: The majority of patients were female (87.5%), with a mean age of 59.15 ± 7.62 years. NP was detected in 55.9% of patients according to the DN4 questionnaire and in 50.7% of patients according to the painDETECT questionnaire. The DN4 score was positively correlated with age (p=0.041; r_s=0.145), visual analogue scale (VAS)-pain at rest (p=0.009; r_s=0.188), VAS-pain at movement (p=0.017; r_s=0.173), Western Ontario and McMaster Osteoarthritis Index (WOMAC) pain score (p=0.030; r_s=0.157), WOMAC stiffness score (p=0.000; r_s=0.253), physical function WOMAC score (p=0.000; r_s=0.271), total WOMAC score (p=0.000; r_s=0.305), Lequesne score (p=0.002; r_s=0.221), and negatively correlated with quadriceps circumference (p=0.008; r_s=-0.210). Whereas, the painDETECT score was positively correlated with VAS-pain at movement (p=0.002; r_s=0.220), WOMAC stiffness score (p=0.043; r_s=0.147), physical function WOMAC score (p=0.017; r_s=0.172), and total WOMAC score (p=0.012; r_s=0.182). NP according to the DN4 was associated with quadriceps circumference (p=0.01), while the painDETECT score was associated with VAS- pain at movement scores (p=0.022) and total WOMAC score (P=0.001).

Conclusion: This study found that NP is common among patients with primary KO and is associated with more painful pathology and functional impairment. These findings highlight the importance of recognizing and managing NP in this population to improve patient outcomes.