Total knee arthroplasty (TKA) is a surgery that aims to restore function and relieve pain in advanced osteoarthritis. The Educational Workshop (EW) for TKA is given to patients in the pre-surgery period to inform them and facilitating their participation in their health process (empowerment). The aim of this study was developing and validating a self-administered questionnaire to evaluate the acquired knowledge after the EW by the patients who will undergo the TKA procedure.

It was a longitudinal and prospective observational study with a sample of TKA candidate patients. The phases for the construction and validation of this ad hoc questionnaire were: Phase 1: A panel of experts who agreed on a final questionnaire of 20 items; Phase 2: Pilot test administered to 47 patients; Phase 3: Final test of 11 items administered to 50 patients, before and after the EW; Phase 4: Re-test, after the EW and 2 weeks after, administered to 58 patients.

One hundred and fifty five patients were included. The Cronbach's alpha coefficient for the item's internal consistency of the final questionnaire, 11 items, was 0.78. To reach the criterion validity, in pre-EW the mean number of hits was: 4.92 (SD=1.78) and in post-EW 10.68 (SD=0.55), a difference that had a statistical significance p<.0001, with no overlap in the 95% CI of the mean: 4.46-5.38/10.54-10.82. The test for stability and reliability, re-test, obtained a mean of right answers 10.87 (SD=0.33) and for the re-test of 10.70 (SD=0.59). The correlation of the interclass coefficient for the re-test was 0.99, which corresponds almost to a maximum concordance.

The questionnaire developed in this study is a reliable and easy tool to evaluate the acquired knowledge in the EW for patients who will be TKA operated.