Multibody simulations of human motion require representative models of the anatomical structures. A model that captures the complexity of the foot is still lacking. In the present work, two detailed 3D multibody foot-ankle models generated based on CT scans using a semi-automatic tool are described. The proposed models consists of five rigid segments (talus, calcaneus, midfoot, forefoot and toes), connected by five joints (ankle, subtalar, midtarsal, tarsometatarsal and metatarsophalangeal), one with 15DOF and the other with 8DOF. The calculated kinematics of both models were evaluated using gait trials and compared against literature, both presenting realistic results. An inverse dynamic analysis was performed for the 8DOF model, again presenting feasible dynamic results.

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In this work, a three-dimensional foot and leg model is proposed, which combines six rigid bodies and five kinematic pairs to produce an articulated system of four segments (toes, mid-forefoot, rearfoot and leg) with thirteen independent degrees-of-freedom. The model is described using a multibody dynamics formulation with natural coordinates and estimated anthropometric parameters. A massless link is used to model the anatomical offset between the talocrural and talocalcaneal joints, avoiding the inclusion of a specific rigid body to model the talus bone. The reliability of the model was tested through its application to the study of the kinematic and dynamic patterns of the human gait. A male subject was analyzed and his data compared with literature, enabling to attest the consistency and realism of the proposed model.

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