Foot Function Assessment and Cross-Cultural Adaptation of the Foot Function Index to Polish in Rheumatoid Arthritis Patients

Aim To assess rheumatoid arthritis (RA) patients’ functional status and to perform a cross-cultural adaptation of the original Foot Function Index (FFI) questionnaire to develop the Polish version. Material and Methods Thirty-one female patients with RA participated in this observational study. The patient’s health statuses were evaluated with the culturally adopted FFI (FFI-PL), the Polish version of SF-36 (SF-36-PL), the Polish version of the Beck Depression Inventory (BDI-PL) and a Visual Analogue Scale of foot pain (VAS-pain). Construct validity, internal consistency and criterion validity were calculated for the FFI Polish version after the translation and cross-cultural adaptation process. Results Subsequent analyses showed numerous significant correlations. The FFI-PL total results were moderately correlated with VAS-pain, BDI-PL and SF-36-PL. The FFI-pain results were highly correlated with the FFI total results. The FFI-disability results were correlated with the BDI-PL and SF-36-PL. Surprisingly, no correlations were found in the study group between FFI-PL results and age, working time, or years since diagnosis. Internal consistency of the Polish FFI ranges from 0.996 to 0.998. Test-retest analysis ranged from 0.985 to 0.994. Conclusions The FFI-PL is an effective tool for assessing RA patients’ functional status. The Polish adaptation of the FFI presents good to excellent psychometric properties. Polish researchers and clinicians may use this tool for foot and ankle assessment and monitoring.