Foot function in rheumatoid arthritis: Correlation between the Rheumatoid and Arthritis Outcome Score and...

Foot function is usually assessed using self-reported outcome measures which remain subjective in patients with rheumatoid arthritis (RA). Physical performance tests were recommended for functional assessment in lower limb osteoarthritis. However, foot function assessment's guidelines in RA are lacking. We aimed to investigate the correlation between a self-reported outcome measure and two performance-based physical tests for assessing foot function in RA patients.

A cross-sectional study was performed over 7 months' period including RA patients. We used Rheumatoid and Arthritis Outcome score (RAOS) as a self-reported functional tool. Physical performance tests were 4-min walk test (4-MWT) and Timed up and go test (TUGT).

Fifty RA patients were included with 96% females and a mean age of 54.7 ± 10.4 years. Foot involvement occurred since the diagnosis of RA in 36% of patients. Foot pain was reported by 68% of patients (48% forefoot), and foot stiffness in 46% of patients. Skin lesions of the feet were found in 78% of patients, 90% had foot deformities and 56% had inflammatory disorders of feet. Radiographic lesions were found in 94% of patients. The most impaired RAOS subscales were Sports and Recreation and Quality of life. Poor physical-based performance was found in 34% of RA patients according to 4-MWT, in 42% of RA patients according TUGT, and in 46% of patients based on at least one performance test. RAOS was negatively correlated to the 4-MWT and positively correlated in the subscales pain, other symptoms, activities of daily living, and Sport/Rec of the RAOS. Poor performance-based physical tests were significantly associated with advanced age, sedentary lifestyle, higher disease activity score and impaired functional status. Foot-related parameters significantly associated with poor performance-based physical tests were: foot pain, foot deformity and inflammatory disorders. Multivariate analysis identified foot deformities and higher functional impairment as predictive factors for lower gait speed (4-MWT) and older age and higher functional impairment for higher duration of TUGT.

RAOS was significantly associated with performance-based physical function. In the era of connected technologies, these results encourage the regular assessment of rheumatoid foot function by the RAOS score through a connected programme using wearable trackers.