Cross-Cultural Adaptation and Validation of the Kazakh Version of the WOMAC Index in Patients with Knee Osteoarthritis

Knee osteoarthritis (KOA) is a prevalent condition associated with pain and reduced physical function worldwide, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is one of the most commonly used disease-specific patient-reported outcome measures. Its use in non-English-speaking populations requires appropriate translation and validation, and no validated Kazakh version has previously been available. This study aimed to translate, culturally adapt, and evaluate the psychometric properties of the Kazakh version of the WOMAC in patients with KOA. A cross-sectional validation study was conducted among 452 patients with clinically diagnosed KOA and 126 healthy individuals, following established international guidelines. The study assessed internal consistency, test–retest reliability, construct validity, content validity, convergent validity, known-groups validity, and floor and ceiling effects. The Kazakh WOMAC demonstrated acceptable to high internal consistency (Cronbach’s α = 0.77–0.88) and good test–retest reliability (ICC = 0.78–0.83). Content validity was excellent (S-CVI/Ave = 0.96), and confirmatory factor analysis supported the original three-factor structure. Expected correlations with SF-36 domains confirmed convergent validity, and WOMAC scores differentiated patients with KOA from healthy individuals, with no relevant floor or ceiling effects observed. The Kazakh version of the WOMAC is a reliable and valid instrument for assessing pain, stiffness, and physical function in Kazakh-speaking patients with KOA.