Reliability and Validity of a New Questionnaire Created to Establish the Presence of Functional Ankle Instability: The IdFAI

Functional ankle instability (FAI) has been widely investigated, yet there remains to be no benchmark measure or universally accepted definition of this pathology. Although numerous studies^1--7 have documented the lasting deficits that exist following an initial ankle sprain, it remains difficult to identify a homogeneous subset of the population who can be classified as having FAI. The current standard of practice by many researchers is to use a self-report questionnaire to determine an individual's incidents of instability. Several self-reported questionnaires have been published in the past decade.^8--15 These include the Ankle Instability Instrument (AII), Ankle Joint Functional Assessment Tool, Chronic Ankle Instability Scale, Cumberland Ankle Instability Tool (CAIT), Foot and Ankle Ability Measure (FAAM), Foot and Ankle Instability Questionnaire, and Foot and Ankle Outcome Score. An investigation of these widely used questionnaires found that no singular instrument could accurately predict whether an individual meets a minimally accepted criteria for FAI.¹⁶ In addition, although many of these questionnaires have established test--retest reliability and are frequently reported in the literature, only limited validity testing has been conducted.

The Identification of Functional Ankle Instability (IdFAI) is a newly published questionnaire that was specifically designed to detect whether individuals meet a minimum criteria necessary for inclusion in an FAI population.¹⁷ The IdFAI is intended to give both researchers and clinicians a simple and effective tool to determine an individual's ankle stability status. The IdFAI is based on 2 previous FAI instruments: the CAIT and the AII. The underlying concept of the IdFAI is to consolidate the elements of each instrument and combine them in a manner that results in a simple and concise means to identify individuals with FAI. One of the main elements included in the IdFAI, which is not in any other questionnaire, is a specific definition of giving way. This definition was provided to ensure that all individuals understood the term and answered questions based on the same definition. The definition included in the questionnaire is: "'Giving way' is described as a temporary uncontrollable sensation of instability or rolling over of one's ankle." This definition was based on the work originally conducted by Freeman,^18,19 as well as on current literature.²⁰

The IdFAI was tested, and the final items appearing on...