Validation of a Japanese patient-derived outcome scale for assessing total knee arthroplasty: comparison with Western Ontario and McMaster Universities osteoarthritis index (WOMAC).

We have developed a Japanese self-administered questionnaire based on an English version of the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) to measure subjective function and pain status of patients who undergo a total knee arthroplasty procedure. Using multiple international cohorts, the performance of the developed Japanese scale was compared to the results of the WOMAC in the United Kingdom, United States, Canada, and Australia. The developed scale showed a comparable level of internal consistency and construct/criterion validity. The responsiveness of the scale was superior to the concurrently measured MOS Short Form 36 Physical Function scale. These results suggest that the developed scale is reliable, valid, and responsive for assessing the effectiveness of total knee arthroplasty in the Japanese context despite the cultural life style differences from Western countries.