A new skeletal model for the ankle joint complex

The talocrural and the talocalcaneal articulations collectively form the ankle joint complex of the human foot and are the focus of investigation of this work. The talocrural articulation enables plantarflexion and dorsiflexion, while the talocalcaneal articulation allows inversion and eversion of the foot. A comprehensive analysis of the literature suggests that the ankle joint complex is modeled in different manners considering approaches with varying complexity levels, which more or less accurately mimic its intrinsic anatomical features. Several studies assume that the foot articulates with the leg via the talocrural articulation only, which is modeled as a revolute joint. Other studies consider the movements allowed by both articulations and model the ankle joint complex as spherical, revolute, or classical universal joints. Most existing approaches do not consider sufficiently accurate anatomical modeling of this joint complex. Thus, this work presents a new skeletal model for the ankle joint complex of the human foot that considers the actual anatomy and movements of the talocrural and the talocalcaneal articulations. The proposed approach uses a modified universal joint, which incorporates a massless link to mimic the actual function of the talus bone. The developed formulation is compared with a model available in the literature, which uses a classical universal joint. The outcomes show that modeling the ankle joint complex as a modified universal joint allows a more realistic representation of the anatomy of the human foot. The main differences between the two joint models are observed in the mediolateral direction.