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.