Impact of midfoot and Hindfoot involvement on functional disability in Korean patients with rheumatoid arthritis

BACKGROUND Foot involvement in rheumatoid arthritis (RA) patients has been reported to severely affect functional capacity and quality of life. We aimed to determine the impact of midfoot and hindfoot involvement on functional disability in Korean patients with RA. METHODS We evaluated the RA involvement and deformity of three regions of the foot (forefoot, midfoot and hindfoot) and ankle using conventional radiography in Korean patients with RA. We compared the clinical features between RA patients with and without foot or ankle involvement. Using multivariable logistic regression analyses, the impact of midfoot or hindfoot involvement on functional disability in RA patients was evaluated. RESULTS Overall, 120 patients with a median age of 48.0 [interquartile range (IQR), 37-56] years and median disease duration of 58.0 (IQR, 10-89) months were included. The prevalence of foot or ankle RA involvement was 74 (61.7%). The number of patients with forefoot, midfoot, hindfoot and ankle involvement was 32 (43.2%), 24 (32.4%), 46 (62.2%) and 4 (5.4%), respectively. Compared to patients without foot or ankle involvement those with such involvement had greater disease activity and functional disability, more of them were treated with biologic agents, and they had a lower health-related quality of life. After adjusting for potential confounders, hindfoot involvement was associated with a higher degree of functional disability. However, walking difficulty was more associated with midfoot involvement rather than with involvement in other regions. CONCLUSIONS In Korean patients with RA, hindfoot involvement is associated with functional disability and midfoot involvement affects walking.