The Importance of Foot Function Assessment Using the Foot Function Index-Revised Short Form (FFI-RS) Questionnaire in the Comprehensive Treatment of Patients with Rheumatoid Arthritis

Background. Foot problems may have a substantial negative impact on rheumatoid arthritis (RA) patients' mobility. They affect walking and the functional capacity to perform daily tasks. Methods. This study included 61 patients with RA and foot pain or swelling. The study group comprised 37 patients (aged 54.3 +/- 9.5 years) with foot lesions, as demonstrated in an ultrasound, and the control group comprised 24 patients (aged 57.3 +/- 11.5 years) without foot lesions. The patients' health statuses were evaluated with the Foot Function Index-Revised Short Form (FFI-RS), the Polish version of the Health Assessment Questionnaire-Disability Index (HAQ-DI), and the Disease Activity Score 28 (DAS 28). Results. The FFI-RS showed significant differences between the study and control groups in total results, as well as in the pain and stiffness subscales. Subsequent analyses showed numerous significant correlations. The FFI-RS total results correlated with the HAQ's standing up, walking, and total results. The FFI-RS pain results correlated with the social issues and HAQ's total results. The FFI-RS difficulty results correlated with the disease's duration. In the study group, there were significant correlations of the FFI-RS stiffness, difficulty, and social issues results with the HAQ's standing up, walking, and total results, and also of the FFI-RS activity limitation results with the HAQ's standing up results. In the control group, there were correlations of the FFI-RS stiffness, difficulty, and activity limitation results with the HAQ's walking and total results. Finally, in the study group, we also found correlations of the FFI-RS total, pain, stiffness, difficulty, and social issues results with the Visual Analog Scale (VAS) results, as well as of the FFI-RS total results with the DAS 28 results. Conclusions. The FFI-RS is an effective tool for assessing RA patients' functional status and can be used to evaluate treatment effects. The FFI-RS detected RA-related changes in the foot joint function in patients without foot lesions, as assessed by ultrasound.