A four-segment kinematic model for clinical description of foot and ankle motion

In this study, a 4 segment rigid body model was developed to investigate isolated foot and ankle kinematics. To obtain clinical data, the foot and ankle were instrumented with 15 retroreflective markers. Once marker coordinates were determined by using a video motion analysis system, the model was employed to transform raw 3-D coordinate data into a more clinically meaningful set of angular and translational relationships between distal and proximal rigid body segments. Three 3-D reference methods were considered in this work, the helical axis, Euler angles, and a set of three independent angles.