Pes planovalgus in RA: a descriptive and analytical study of foot function determined by gait analysis.

OBJECTIVE: To compare gait and foot function between rheumatoid arthritis (RA) patients with painful pes planovalgus deformity and healthy age- and sex-matched adults.

METHODS: Gait analysis was undertaken in 23 RA patients (14 female and 9 male, mean age 52.3 years, mean disease duration 6.6 years) and 23 healthy adults (14 female and 9 male, mean age 49.5 years). Gait measurements included temporal and spatial parameters, plantar pressures and three-dimensional (3D) kinematics at the ankle joint complex (AJC). The mean differences between the groups and associated confidence intervals were calculated using the t distribution.

RESULTS: RA patients showed longer gait cycle (mean difference 0.15 sec and 0.14 sec for right and left limbs, respectively) and double-limb support times (mean difference 8.3% and 7.9% for right and left limbs, respectively), shorter stride length (mean difference -0.31 m for right and left limbs), slower walking speed (mean difference -0.39 m/sec) and lower cadence (mean difference -16.6 steps/min). In comparison with the normal group, RA patients had greater AJC dorsi/plantarflexion range of motion (ROM) (mean difference 5.7 ( degrees )) and inversion/eversion ROM (mean difference 2.9 ( degrees )). The frontal plane position of the AJC was more everted at specific stance periods (mean difference at heel strike -2.4 ( degrees ) and at midstance -4.0( degrees )). Furthermore, both the peak eversion (mean difference -4.1 ( degrees )) and summated eversion motion as a function of time (mean difference -313.9 ( degrees )) were greater in the RA group. The pes planovalgus foot in RA was characterized by increases in peak pressure (mean difference 34.3 kPa), pressure-time integral (mean difference 18.2 kPa.sec), peak force (mean difference 1.7 N), force-time integral (mean difference 0.7 N.sec), contact time (mean difference 9.8% roll over process) and contact area (mean group difference 3.4 cm(-2)) in the medial midfoot. Further changes in the load pattern in the forefoot were observed in the RA patients, namely increases in the peak pressure (mean difference 96.4 kPa), pressure-time integral (mean difference 58.4 kPa.sec), and contact area (mean difference 1.7 cm(-2)) in the medial forefoot region and reduction in contact area (mean difference -3.9 cm(-2)), peak force (mean difference -7.2 N) and force-time integral (mean difference -1.6 N.sec) in the lateral forefoot.

CONCLUSIONS: Painful pes planovalgus deformity in RA is associated with global changes in gait, and localized structural and functional changes in the foot which can be accurately measured using clinical gait analysis.