Measurement properties of the Foot Function Index (FFI) questionnaire: A systematic review

Large numbers of people are subject to alterations and pathologies in the foot. To quantify how these problems of foot function affect the quality of life, clinicians and researchers have developed measures such as the Foot Function Index (FFI). Our aim is to determine the methodological quality of the FFI including adaptations to other languages.

The studies considered in this review were extracted from the PubMed, Embase and CINAHL databases. The inclusion criteria were followed: (1) studies of patients with no previous foot or ankle pathology and aged over 18 years; (2) based on English-language patient-reported outcome measures that assess foot function; (3) the patient-reported outcome measures should present measurement properties based on COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) criteria.

The systematic review was conducted following the COSMIN criteria to establish the methodological quality of the original FFI, together with its variants and adaptations. The last search was carried out in May 2024.

Of the 1994 studies obtained in the preliminary search, 20 were eligible for inclusion in the final analysis. These results are the validations and cross-cultural adaptations to the following languages: the original FFI has cross-cultural adaptation in 13 languages and the FFI-Revised Short Form has been adapted and validated for use in 2 languages.

In terms of methodological quality, the FFI-Revised Short Form questionnaire is a valuable instrument for evaluating ankle and foot function and could usefully be expanded to be available in more languages.