Objectively-assessed Foot and Ankle Characteristics in People With Systemic Lupus Erythematosus: A Comparison With Age- and Sex-matched Controls

OBJECTIVE: To objectively identify foot and ankle characteristics in patients with systemic lupus erythematosus (SLE) compared to age- and sex-matched controls. METHODS: A total of 54 patients with 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, vibration perception threshold (VPT), ankle brachial index (ABI), plantar pressure, and spatiotemporal gait characteristics. Self-reported measure of foot pain and impairment were also assessed using a 100-mm foot pain visual analog scale. Data were analyzed 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 (odds ratio [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: Patients with SLE experience a wide range of foot symptoms. This study has provided objective evidence of foot and ankle disease in patients 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.