Foot Functional Disability in Rheumatoid Arthritis: The Involvement of Body Mass Index

Introduction: Overweight and obesity are common in patients with Rheumatoid Arthritis (RA), with a probable impact on bearing foot joints. Aim: Our study aimed to explore the impact of Body Mass Index (BMI) on foot health parameters in RA patients. Methods: It was a cross-sectional study. Domains of foot health explored were: foot pain (Numeric Rating Scale), foot-related activity limitations (Foot Function Index (FFI), and WOMAC scale), foot synovitis, foot deformity (Platto Score (PS)), radiological joint damage and footwear problems. Results: Fifty RA were included, 82% were female. The mean age was 45.68 ± 10.3 years. The mean DAS28-CRP was 3.25 ± 0.98. Sixty-six percent were overweight or obese, with a mean BMI of 29 Kg/m² ± 5.74. The average foot pain intensity while walking was 6 ± 1.75. The mean swollen foot joint was 2.2 ± 1.55. The average foot structural index was 7.8 ± 2.73. The mean FFI Disability score was 32 ± 14.2 and WOMAC score was 33.8 ± 13.98. Half of our patients had footwear problems predominantly because of claw toe (40%). High BMI was significantly correlated with foot pain and foot-related activity limitations. It was also correlated with foot deformities assessed with PS (B=4.78; CI(3.87-5.68); p = 0.02), foot synovitis (OR=4.66, CI(2.61-8.32); p < 0.001) and problems with footwear (OR= 0.32; CI(0.18-0.56); p = 0.05). However, it was significantly associated with less radiological joint damage (CI(-0.7-1.1); p = 0.01) and lower foot sharp score (B = -13.9; CI(-0.34-0.01); P = 0.06). Conclusion: Despite our findings of a possible protective effect of obesity on structural damage, obesity is still an important cause of increased pain, functional disability, and impaired QoL in RA patients.