Cross-cultural adaptation and reliability of the Italian version of the Foot Function Index (FFI-I) for patients with plantar fasciitis.

Aim: The aim of this paper was to translate and cross-culturally adapt the FFI to the Italian language, and to assess the reliability of the Italian version of the FFI (FFI-I) for plantar fasciitis.

Methods: Fifty symptomatic patients affected by plantar fasciitis completed the FFI-I scale twice, at interval of one week. The translation of the FFI was performed according to international standards for translation of questionnaires. Test-retest reliability was evaluated using intraclass correlation coefficient (ICC). Internal consistency was measured by Cronbach α coefficient. Ceiling and floor effects were assessed.

Results: The process resulted in an intelligible version of the questionnaire. The reliability of the FFI-I was adequate, with an ICC ranging from 0.86 to 0.98 for test-retest reliability. The FFI-I showed an excellent internal consistency, ranging from 0.93 to 0.99 for all subscales. Three items involving disability and four items involving activities restrictions had highest proportion of floor score.

Conclusion: The FFI-I is a reliable and valid instrument to assess clinical severity in patients with plantar fasciitis and it is suitable for daily practice. We suggest evaluating the total FFI-I score along with the distinct scores of the three subscales of the FFI-I in order to interpret more correctly minor changes in patient status during repetitive outcome assessments.