Purpose: This study aimed to determine the differences in foot muscle morphology and 3D multisegmental foot kinematics during walking between symptomatic and asymptomatic individuals with pronated feet (pronators) in a physically active population. Methods: A total of 30 young physically active adults with pronated feet participated in this study, with 15 of them having recurring overuse injuries in the lower extremity in the 6 months prior to the test. A pronated foot was identified as having a foot posture index score between 6 and 12. An ultrasound system was used to measure the cross-sectional area and thickness of foot muscles of interest, including peroneus muscles, flexor digitorum longus and brevis, and abductor hallucis. Foot kinematic data during walking was collected using a 3D motion capture system incorporating the Oxford Foot Model. Results: The symptomatic pronators demonstrated smaller cross-sectional area of flexor digitorum longus and abductor hallucis, and thinner peroneus muscles and abductor hallucis than their asymptomatic counterparts. The symptomatic pronators also displayed higher forefoot peak abduction during the stance phase of walking. Conclusion: There are differences in both extrinsic and intrinsic foot muscle morphology between symptomatic and asymptomatic pronators in a physically active adult population. Strengthening foot muscles may contribute to injury prevention in pronators. Large forefoot abduction instead of large rearfoot eversion during walking might be the indicator of pain in physically active pronators. Findings of this study may have implications on the underlying mechanisms of overuse injuries in individuals with pronated feet. K E Y W O R D S foot posture, forefoot abduction, intrinsic foot muscle, multisegment foot model, recreational runners | 1767 ZHANG et Al.