Foot pain and disability in patients with ankylosing spondylitis is associated to disease activity

ABSTRACT BACKGROUND AND OBJECTIVES: The feet may be involved in patients with ankylosing spondylitis (AS), causing pain and walking difficulties. This research aimed to study the involvement of the foot in a sample of Brazilian patients with AS. METHODS: The Brazilian version of the Foot Function Index (FFI-BR) was applied to 103 individuals (57 AS patients and 46 controls). Clinical profiles were obtained in AS patients as well as the measurement of disease activity by the ASDAS (Ankylosing Spondylitis Disease Activity Score)-ESR (erythrocyte sedimentation rate), ASDAS-CRP (C reactive protein) and BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) and function by BASFI (Bath Ankylosing spondylitis functional score). RESULTS: Only 19.2% of AS patients did not have any foot complaints and the FFI-BR score presented worse results than the control group (p = 0.02). The "pain" domain of FFI-BR scored highest in AS patients, followed by "disability". There was no association between the results of the FFI-BR and the clinical profile of patients with AS, but there was an association between the score and the disease activity indexes (r = 0.50, p = 0.003 with ASDAS-ESR; r = 0.44, p = 0.005 with ASDAS-CRP; and r = 0.60, p < 0.0001 with BASDAI). The BASFI also showed a positive correlation (r = 0.72; p < 0.0001). CONCLUSION: Pain and disability are common in AS patients and these symptoms are associated with disease activity.