What Is the Best Questionnaire for Monitoring the Physical Characteristics of Patients with Knee Osteoarthritis in the Brazilian Population?

OBJECTIVE To measure the validity and reliability of the WOMAC, IKDC and Lysholm questionnaires among patients with knee osteoarthritis and determine the influence of age on their scores. METHOD Fifty-seven patients diagnosed with primary osteoarthritis of the knee answered the SF-36, WOMAC, IKDC and Lysholm questionnaires. Validity was tested by measuring the correlation (Pearson's correlation coefficient, "r") between the questionnaires. Internal consistency was measured using Cronbach's α and concordance was measured through the Altman-Bland graphical representations and survival concordance. To determine the influence of age on the results, we correlated this variable with the scores from the three knee questionnaires using Pearson's coefficient of determination ("r2"). RESULTS IKDC (0.62) and WOMAC (0642) showed moderate to strong correlations in relation to the summarized physical capacity score of the SF-36, while Lysholm showed moderate correlations (0.555). The Cronbach α values for IKDC, WOMAC and Lysholm were 0.811, 0.959 and 0.734, respectively. Despite the strong correlations between IKDC and WOMAC (0.843), Lysholm and WOMAC (0.759) and IKDC and Lysholm (0.858), the Bland-Altman graphical representations and survival concordance showed that the concordance between the three questionnaires was low. IKDC, Lysholm and WOMAC showed coefficients of determination (r2) with age of 0.004, 0.010 and 0.043, respectively. CONCLUSION Age was not found to be a limiting factor for the use of any of the questionnaires applied in this study. The concordance tests and correlations with the physical components of SF-36 suggest that WOMAC is more appropriate for assessing physical capacities and limitations relating to physical traits, while IKDC seems more appropriate for assessing the functional limitations relating to pain.