Translation and validation of the 12-item Oxford knee score for use in Finland

BACKGROUND The focus in the reporting of results after total knee replacement (TKR) has changed from surgeon/radiologist-based scores to patient-reported outcome measures (PROMs). The questionnaires used in subjective outcome are often originally published in English and need to be validated in different languages. The aim of our study was to investigate the feasibility, validity, reliability, and responsiveness of the Finnish language version of the Oxford Knee Score (OKS-S) questionnaire. METHODS The original OKS questionnaire was translated using a forward/backward protocol. The OKS-S questionnaire was sent to 225 patients who were scheduled to undergo TKR surgery. The assessment was repeated 1 year after the index operation. Half of the patients also received the RAND-36 questionnaire with the OKS-S questionnaire and the other half the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire. 30 patients twice received the OKS-S questionnaire preoperatively for the test-retest assessment. RESULTS Feasibility was acceptable with a response rate of 96% in both pre- and postoperative assessments. Correlation between OKS-S questionnaire and all domains of the KOOS questionnaire and the physical domains in the RAND-36 questionnaire was high, and confirmed both good criterion and convergent validity. Content validity was good since no ceiling or floor effect was observed. In the test-retest assessment, all but 2 patients were within the 95% limits of agreement. Responsiveness was large according to effect sizes. CONCLUSIONS Our data suggests that the OKS-S questionnaire is suitable for the assessment of both the preoperative status and the outcome of TKR in Finnish speaking patients.