A 1-Dof parallel spherical wrist for the modelling of the knee passive motion

The passive motion of the knee, i.e. the motion in virtually unloaded condition, is efficiently modelled by means of a parallel spherical wrist. Compared to previously presented models, it results in a much simpler solution, with a lower number of members and kinematic pairs. The model is used to replicate the passive motion of an experimentally analysed knee. Finally, the accuracy of this new model is compared to that of a more complex one, previously presented in the literature, which already proved to be effective.