Translation, cross-cultural adaptation, and psychometric properties of the Thai version of the Identification of Functional Ankle Instability (IdFAI-THAI) questionnaire.

Background: This study developed a Thai version of the Identification of Functional Ankle Instability (IdFAI-THAI) questionnaire.

Methods: To determine construct validity, 200 participants with a history of lateral ankle sprain completed the IdFAI-THAI, the Modified Thai Lower Extremity Functional Scale (LEFS), the Visual Analog Scale of Instability (VAS-I), and the Thai Foot and Ankle Ability Measure (FAAM). Eight days later, 100 randomly selected participants refilled the IdFAI-THAI to assess test-retest reliability and internal consistency.

Results: The IdFAI-THAI moderate correlated with the LEFS (r = -0.62), the VAS-I (r = 0.62), and the FAAM (r = -0.63 and -0.69 for the activities of daily living and sports subscales, respectively). The IdFAI-THAI had good test-retest reliability (ICC = 0.89) and excellent internal consistency (Cronbach's alpha = 0.94). Ceiling and floor effects were absent.

Conclusion: The valid and reliable IdFAI-THAI can identify chronic ankle instability among Thai speakers in clinical and research settings.