Human in vivo midtarsal and subtalar joint kinematics during walking, running, and hopping

The interaction among joints of the midtarsal complex and subtalar joint is essential role for locomotor function; however, its complexity poses substantial challenges in quantifying their motions. We determine the mobility of these joints across locomotion tasks and investigate their alignment with individual talus morphology. Utilizing highly accurate biplanar videoradiography, three-dimensional bone kinematics were captured during walking, running, and hopping. We calculated the axis of rotation of each midtarsal and subtalar joint for the landing and push-off phases, respectively. A comparison was made between these rotation axes and the morphological subtalar axis. Measurement included total rotation about, the orientation of the rotation axes in the direction of the subtalar joint and its deviation via spatial angles for both phases. The rotation axes of all three bones relative to the talus closely align with the morphological subtalar axis. This suggests that the midtarsal and subtalar joints’ motions might be described by one commonly oriented axis. Despite having such axis, the location of axes and ranges of motion differed among the bones. Our results provide a novel perspective of healthy foot function across different sagittal plane-dominant locomotion tasks underscoring the importance of midtarsal and subtalar motion with respect to subject-specific talus morphology. ### Competing Interest Statement AVB, LW, MR, and LK declare that they have no conflict of interest. AVB is supported by the International Society of Biomechanics Matching Dissertation Grant. LW is funded by the Natural Sciences and Engineering Research Council Postdoctoral Fellowship (NSERC PDF: 558140-2021). MR is funded by the Natural Sciences and Engineering Research Council of Canada Discover Grant (RGPIN/04880-2022) and LK by the Australian Research Council Discover Early Career Research Award (DE200100585).