Reliability and Validity of the Korean Version of the Foot Function Index

Although translated versions of the Foot Function Index (FFI) in several languages are available, the absence of a Korean version has precluded comparing the data from Korea with the data from other countries using the FFI. We, therefore, evaluated the reliability and validity of the adapted Korean version of the FFI. We translated the English version of the FFI into Korean and back into English. We mailed the Korean version of the visual analog scale, FFI, and the previously validated Medical Outcomes Study Short-Form 36-item questionnaire (SF-36) to 121 patients with treated foot complaints. To evaluate the test-retest reliability and internal consistency, we used the intraclass correlation coefficient and Cronbach's α, respectively. We also evaluated the concurrent and construct validity of Korean version of the FFI by comparing the visual analog scale and SF-36. Cronbach's α was 0.91 and 0.95 for the pain and disability subscales, respectively. The reproducibility was good, and a strong correlation between the FFI and the SF-36 and visual analog scale with related content was observed, indicating good construct validity.The Korean version of the FFI is a reliable and valid questionnaire for the self-assessment of pain and disability in Korean patients with foot complaints.