A new spatial kinematic model of the lower leg complex: a preliminary study

The importance of the human joint passive motion, i.e., the articulation motion in virtually unloaded conditions, for the study of human diarthrodial joints has been widely recognized. Recently, it has been shown that equivalent mechanisms make it possible to obtain physicalmathematical models that can replicate the articular passive motion well. These models also represent a useful tool for both pre-operation planning and prosthesis design. Although the human ankle joint has been extensively investigated, studies that examine the kinematic behaviour of the tibio-talar joint and also outline the motion of the fibula bone are still lacking. This paper focuses on the 3D kinematic model of the articulation that involves four bones: the tibia, fibula, talus and calcaneus. In particular, a new spatial equivalent mechanism with one degree of freedom is proposed for the passive motion simulation of this anatomical complex. The proposed mechanism is believed to play an important role for future developments of models of the entire human lower limb.