Cross-cultural adaptation and validation of the Portuguese version of the Oxford Knee Score (OKS)

The purpose of this study was to translate and culturally adapt the Oxford Knee Score (OKS) to the Portuguese language and to test its reliability and validity. This new version was obtained with forward/backward translations, consensus panels and a pre-test. The Portuguese OKS and Medical Outcomes Study - 36 item Short Form (SF-36) questionnaires, visual analog scales (VAS) of pain and disability, and a form for the characteristics of the patients were administered to 80 subjects who underwent total knee replacement (TKR) for severe knee osteoarthritis (OA). Reliability was acceptable with a Cronbach's alpha coefficient of 0.87, and an intraclass correlation coefficient (ICC) of 0.97. Construct validity was supported by the confirmation of three predefined hypotheses involving expected significant correlations between OKS scale, SF-36 subscales and VAS that represent similar constructs. The Portuguese OKS exhibited suitable psychometric properties, in terms of internal consistency, reproducibility and construct validity.