title: Development of the Identification of Functional Ankle Instability (IdFAI).
abstract: BACKGROUND
  Self-reported questionnaires are a common method used in identifying individuals with ankle instability. Recently a study illustrated the singular use of any of the most frequently utilized questionnaires failed to significantly predict ankle stability status. Therefore, the purpose of this article was to present information related to the development of the Identification of Functional Ankle Instability (IdFAI).
  
  
  METHODS
  Volunteers (n = 278; 125 males, 153 females, 19.8 ± 1.4 years) completed the IdFAI on one occasion. An exploratory factor analysis was conducted with principal axis factoring as the extraction method with varimax rotation. Additionally, a discriminant function analysis was conducted to identify a discrimination score and to evaluate the accuracy of the questionnaire.
  
  
  RESULTS
  The factor analysis revealed: factor 1 (four questions) explained 53.7% of the variance, factor 2 (four questions) with an additional 17.4%, and factor 3 (two questions) an additional 6.3%. Overall, these factors accounted for 77.4% of the variance. There was a distinct discrimination score of 10.3 to identify people who have the minimally accepted criteria for FAI. Overall, the IdFAI has an accuracy of 89.6%.
  
  
  CONCLUSIONS
  This investigation showed that the IdFAI was a feasible and appropriate way to identify individuals with FAI.
  
  
  CONCLUSIONS
  We suggest clinicians and researchers utilize the IdFAI to identify individuals with functional ankle instability since it is a short, simple, easy questionnaire to administer and take, and has been shown to have excellent accuracy.
authors.affiliation: Indiana University, Bloomington, IN 47408, USA. jesimon@indiana.edu
authors.forename: Janet
authors.initials: J
authors.lastname: Simon
authors.forename: Matthew
authors.initials: M
authors.lastname: Donahue
authors.forename: Carrie
authors.initials: C
authors.lastname: Docherty
mesh_terms: D000293:Adolescent; D000328:Adult; D000843:Ankle Joint; D005163:Factor Analysis, Statistical; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis*; D008297:Male; D057566:Self Report; D013180:Sprains and Strains / Q000175:diagnosis; D011795:Surveys and Questionnaires; D055815:Young Adult