RESUMO
OBJECTIVES: The aim of this research was to describe the translation and cultural adaptation, and to test the validity and reliability of the Brazilian version of the Identification of Functional Ankle Instability (IdFAI) questionnaire. DESIGN: This was a clinical measurement. SETTING: This research took place at the Federal University of Sao Paulo in Brazil. PARTICIPANTS: Fifty college students participated in the translation and cultural adaptation, while another 50 students participated in the measurements (validity and reliability). MAIN OUTCOME MEASURES: The cross-cultural adaptation of the Brazilian IdFAI was accomplished using standard guidelines. For the validity and reliability, the individuals were asked to complete the IdFAI tests on the same day, and after two weeks maximum. The validity was assessed by correlating the Brazilian IdFAI with the Visual Analog Scale for Instability (VAS-I), the Cumberland Ankle Instability Tool (CAIT), and the Lower Extremity Functional Scale (LEFS) using Spearman's correlation coefficient. The test-retest reliability and internal consistency were determined by using an intraclass correlation (ICC2,1) and Cronbach's α, respectively. The agreement [standard error of measurement (SEM) and minimal detectable change at 90% (MDC90)] and the floor and ceiling effects were also assessed. RESULTS: The Brazilian IdFAI had strong correlation with the CAIT and moderate correlations with the VAS-I and LEFS scale, with excellent reliability, internal consistency and agreement. No ceiling or floor effects were observed. CONCLUSION: The Brazilian IdFAI questionnaire is a valid and reliable instrument to identify functional ankle instability. It can be used in both clinical and research settings.