Reliability and validity of Persian version of Western Ontario and McMaster Universities Osteoarthritis index in knee osteoarthritis

Introduction: This study aimed to test the reliability and validity of translated and adapted version of Western Ontario and McMaster (WOMAC) questionnaire in Persian language speaking patients with symptomatic osteoarthritis (OA) of the knee. Methods: 100 consecutive patients, attended 3 major referral rehabilitation centers at the northwest of Iran, were asked to answer two disease-specific questionnaires WOMAC and knee injury and osteoarthritis outcome score (KOOS). The same patients were readmitted for refilling the same questionnaire 24-48 hours after the first visit. Internal consistency, reliability, and validity were assessed. Results: There were statistically significant correlations between WOMAC and KOOS in case of the pain (P < 0.001) and stiffness (P = 0.004) scores subclass, the sum of difficulty with performing daily activity (DPDA) score (P = 0.001) and also the total score (P < 0.001). Internal consistency with Cronbach’s alpha for the pain, stiffness, and physical function subscales were 0.96, 0.98, and 0.99, respectively. Internal consistency with Cronbach’s alpha for the total score of WOMAC was 0.99. Conclusion: We found that this Persian version of WOMAC questionnaire is a reliable and valid version for evaluating the knee OA.