Validity and reliability of the French translation of the Identification of Functional Ankle Instability (IdFAI).

Purpose: To translate and validate the Identification of Functional Ankle Instability (IdFAI) into French.

Methods: The IdFAI was translated according to international recommendations. Discriminative power, floor and ceiling effects, construct validity (including confirmatory factorial analysis (CFA)), internal consistency and test-retest reliability were measured. Standard Error of Measurement (SEM) and Smallest Detectable Change (SDC) were also calculated.

Results: 160 participants were included. The IdFAI-F showed a very good test-retest reliability (ICC = 0.95). The SEM was 1.37 and the MDC was 3.79. The internal consistency was moderate (Cronbach's alpha coefficient = 0.68). The correlation between the IdFAI and the Cumberland Ankle Instability Tool (CAIT) was high (r = -0.75, p < 0.001). No floor, nor ceiling effects were observed. The CFA analyses did not confirm the factor structure proposed by the authors of the original English version.

Conclusions: The IdFAI-F is a valid and reliable tool to accurately identify and measure chronic ankle instability in research and clinical settings for French-speaking individuals.