PURPOSE: The Western Ontario and McMasterUniversities Arthritis (WOMAC) index has been used to measure the outcome of total knee replacement (TKR), but studies on its reliability and validity are limited. The present study examined the reliability and validity of this index for patients with knee osteoarthritis who underwent TKR.METHODS: Seventy-one inpatients and outpatients who underwent bilateral TKR for knee osteoarthritis were included in this study. The pain assessment scale and WOMAC index were used to evaluate the participants every two weeks to examine the test-retest reliability, internal consistency, and construct validity.