Skeletal kinematics of the midtarsal joint during walking: Midtarsal joint locking revisited.
The kinematics of the human foot complex have been investigated to understand the weight bearing mechanism of the foot. This study aims to investigate midtarsal joint locking during walking by noninvasively measuring the movements of foot bones using a high-speed bi-planar fluoroscopic system. Eighteen healthy subjects volunteered for the study; the subjects underwent computed tomography imaging and bi-planar radiographs of the foot in order to measure the three-dimensional (3D) midtarsal joint kinematics using a 2D-to-3D registration method and anatomical coordinate system in each bone. The relative movements on bone surfaces were also calculated in the talonavicular and calcaneocuboid joints and quantified as surface relative velocity vectors on articular surfaces to understand the kinematic interactions in the midtarsal joint. The midtarsal joint performed a coupled motion in the early stance to pronate the foot to extreme pose in the range of motion during walking and maintained this pose during the mid-stance. In the terminal stance, the talonavicular joint performed plantar-flexion, inversion, and internal rotation while the calcaneocuboid joint performed mainly inversion. The midtarsal joint moved towards an extreme supinated pose, rather than a minimum motion in the terminal stance. The study provides a new perspective to understand the kinematics and kinetics of the movement of foot bones and so-called midtarsal joint locking, during walking. The midtarsal joint continuously moved towards extreme poses together with the activation of muscle forces, which would support the foot for more effective force transfer during push-off in the terminal stance.