The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in Persian Speaking Patients with Knee Osteoarthritis

Osteoarthritis of the knee is the most common chronic joint disease that involves middle aged and elderly persons. There are different clinical instruments to quantify the health status of patients with knee osteoarthritis and one example is the WOMAC score that has been translated and adapted into different languages. The purpose of this study was cultural adaptation, validation and reliability testing of the Persian version of the WOMAC index in Iranians with knee osteoarthritis. We translated the original WOMAC questionnaire into Persian by the forward and backward technique, and then its psychometric study was done on 169 native Persian speaking patients with knee degenerative joint disease. Mean age of patients was 53.9 years. The SF-36 and KOOS were used to assess construct validity. Reliability testing resulted in a Cronbach’s alpha of 0.917, showing the internal consistency of the questionnaire to be a reliable tool. Inter-correlation matrix among different scales of the Persian WOMAC index yielded a highly significant correlation between all subscales including stiffness, pain, and physical function. In terms of validity, Pearson`s correlation coefficient was significant between three domains of the WOMAC with PF, RP, BP, GH, VT, and PCS dimensions of the SF-36 health survey (P<0.005) and KOOS (P <0.0001). The Persian WOMAC index is a valid and reliable patient- reported clinical instrument for knee osteoarthritis.