Higher body mass index is associated with lower foot health in patients with rheumatoid arthritis: baseline results of the Amsterdam-Foot cohort

Objective: Obesity is highly prevalent in patients with rheumatoid arthritis (RA), with likely impact on weight-bearing foot joints. We explored the associations between body mass index (BMI) and measures of foot health in patients with RA and foot complaints. Method: We examined patients with RA presenting for their first custom-made therapeutic footwear or foot orthoses. Domains of foot health comprised: foot pain, foot-related activity limitations, forefoot plantar pressure, foot synovitis, and foot deformity. In regression analyses, BMI was the independent variable and foot health domains were the dependent variables. Results: The cohort at baseline comprised 230 patients [mean ± sd age 58 ± 13 years, 80% female, mean ± sd disease duration 10 ± 9 years, and median (interquartile range) BMI 26.7 (23.5–30.1) kg/m²]. Small to modest statistically significant associations were found in the majority of the measures studied between a higher BMI and more foot pain, more foot-related activity limitations, higher in-shoe measured forefoot plantar pressure, and the presence of foot synovitis. No relationships were found between BMI and barefoot measured forefoot plantar pressure or foot deformity. Conclusion: BMI is negatively associated with foot health in patients with RA. Although the clinical relevance of our findings for an individual patient is not immediately obvious, future research should consider BMI as a potential therapeutic target to improve foot health.