The study aimed to compare the reliability, responsiveness and construct convergent validity of four questionnaires (Western Ontario and McMaster Universities Osteoarthritis Index, Activities of Daily Living of the Knee Outcome Survey, Oxford Knee Score, and the 12-item Short Form Health Survey) in total knee arthroplasty patients. Seventy-nine patients completed the questionnaires before surgery and 6 months later. The reliability was high for all instruments with intraclass correlation coefficients from 0.81 to 0.96 and SEMs from 6.6% to 28.3% of mean scores. The score changes after surgery were three- to five-fold the instruments' measurement error. The responsiveness was large for all instruments. In conclusion most of the selected instruments were reliable and responsive. It was not possible to clearly identify a "best" or "better" tool and hence all can be considered useful, with the reported psychometric properties serving to guide the choice of instrument for a given purpose.
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