A Sequential Approach for Modelling the Knee Joint Stiffness

Mathematical models of the knee joint are important tools which have both theoretical and practical applications. Many models have been presented in the literature as a confirmation of their scientific and practical relevance (Hefzy and Cooke, 1996). Some of them are purely kinematic and a few of these (Wilson and O’Connor, 1997; Parenti-Castelli and Di Gregorio, 2000; Sancisi and Parenti-Castelli, 2007) simulate the knee passive motion, i.e. the tibia-femur relative motion under virtually unloaded conditions. Others are kinetostatic (Blankevoort et al., 1991) or dynamic (Pandy et al., 1997). In some cases these models are defined from average data taken from the literature, otherwise they are based on experimental data and try to fit a particular required task. In this paper a novel approach is proposed to define more and more sophisticated models of a human articulation. In particular, a stiffness model of the knee is developed starting from a simple although efficient kinematic model of the passive motion recently presented in (Parenti- Castelli and Di Gregorio, 2000). The results obtained from the stiffness model are presented and then compared with published experimental data.