Objective. To objectively identify foot and ankle characteristics in people with SLE compared to age- and sex-matched controls.

Methods. 54 SLE and 56 control participants attended a study visit designed to comprehensively assess the foot and ankle. Objectively-assessed foot characteristics included muscle strength, joint motion, foot posture, foot problems, protective sensation, vibratory perception (VPT), ankle brachial index (ABI), plantar pressure and spatiotemporal gait characteristics. Self-reported measure of foot pain and impairment were also assessed including a 100mm foot pain visual analogue scale. Data were analysed using regression models. Plantar pressure and gait models were adjusted for walking velocity, body mass index and foot pain.

Results. Compared to controls, participants with SLE had lower muscle force for plantarflexion, dorsiflexion, inversion and eversion (all P<0.001), higher foot posture indices (P=0.007), higher foot problem scores (P=0.001), higher VPT (P=0.001) and more frequent abnormal ABI (OR=3.13, P=0.044). Participants with SLE also had lower peak pressure and higher pressure time integrals for all foot regions (all P<0.001), lower step and stride length, velocity and cadence and higher step, swing, stance and single and double support times compared to controls (all P<0.001). Compared to controls, participants with SLE also reported greater foot pain (P<0.001).

Conclusion. People with SLE experience a wide-range of foot complaints. This study has shown objective evidence of foot and ankle disease in people with SLE, including reduced muscle strength and altered gait patterns when compared to controls. This highlights the importance of foot health assessments as part of SLE management.