The impact of rheumatoid arthritis on foot function in the early stages of disease: a clinical case series

Abstract

Background: Foot involvement occurs early in rheumatoid arthritis but the extent to which this impacts on the structure and function leading to impairment and foot related disability is unknown. The purpose of this study was to compare clinical disease activity, impairment, disability, and foot function in normal and early rheumatoid arthritis (RA) feet using standardised clinical measures and 3D gait analysis.

Methods: Twelve RA patients with disease duration < or =2 years and 12 able-bodied adults matched for age and sex underwent 3D gait analysis to measure foot function. Disease impact was measured using the Leeds Foot impact Scale (LFIS) along with standard clinical measures of disease activity, pain and foot deformity. For this small sample, the mean differences between the groups and associated confidence intervals were calculated using the t distribution

Results: Moderate-to-high foot impairment and related disability were detected amongst the RA patients. In comparison with age- and sex-matched controls, the patients with early RA walked slower (1.05 m/s Vs 1.30 m/s) and had a longer double-support phase (19.3% Vs 15.8%). In terminal stance, the heel rise angle was reduced in the patients in comparison with normal (-78.9 degrees Vs -85.7 degrees). Medial arch height was lower and peak eversion in stance greater in the RA patients. The peak ankle plantarflexion power profile was lower in the patients in comparison with the controls (3.4 W/kg Vs 4.6 W/kg). Pressure analysis indicated that the RA patients had a reduced lesser toe contact area (7.6 cm2 Vs 8.1 cm2), elevated peak forefoot pressure (672 kPa Vs 553 kPa) and a larger mid-foot contact area (24.6 cm2 Vs 19.4 cm2).

Conclusion: Analysis detected small but clinically important changes in foot function in a small cohort of RA patients with disease duration <2 years. These were accompanied by active joint disease and impairment and disability.

Figure 1

Selected gait parameters normalised for 100% stance (each graph is individually scaled and the gray band represents the mean ± 1 SD for the able-bodied adults and the solid line is the mean ± 1 SD error bars for the RA patients. A – Initial foot-to-floor and terminal stance heel rise angles during stance, measured as the angle of the plantar surface of the foot to the horizontal. Positive angles decreasing to zero indicate increasing foot-to-floor contact, zero indicates foot flat, and increasing negative angles indicate progressive heel rise; B – frontal plane motion of the rearfoot in the shank coordinate system during stance phase (+ inversion/- eversion); C – ground reaction forces normalised to body mass acting perpendicular to the plantar aspect of the foot; D – sagittal plane ankle joint power during stance).