Translation, validity, and reliability of the Foot Posture Index (FPI-6) - Turkish version

The aim of this study was to translate the English version of the Foot Posture Index (FPI-6) into Turkish and to examine its psychometric properties.

After the forward-backward translation process, the internal consistency and intra - and inter-rater reliability were evaluated by using Cronbach's α and Intraclass Correlation Coefficient (ICC_2,k) (two-way random effects model with absolute agreement type), respectively. The agreement between reliability assessments was investigated by the standard error of measurement (SEM) and the minimal detectable change (MDC_95%). Criterion validity was assessed in relationship between the Turkish FPI-6 and Foot Function Index (FFI) and the American Orthopedic Foot and Ankle Society (AOFAS).

The study was completed with 45 patients with foot/ankle problems. The internal consistency (Cronbach's α = 0.85; 0.78, respectively), intra-reliability (ICC_2,k = 0.96; 0.94, respectively), and inter-reliability (ICC_2,k = 0.93; both of them) of the Turkish version of the FPI-6 were excellent for the dominant and non-dominant lower limb. The SEM was low, and the agreement was considered to have high absolute reliability, as demonstrated by the smallest change in measurement error. The Turkish FPI-6 also had moderate correlations with the FFI and AOFAS (p < .05).

It has been proven that the Turkish FPI-6 is valid and reliable and can be used by Turkish-speaking researchers and clinicians in patients with various foot-ankle problems.