Dynamic Modeling of Human Articulating Joints

Abstract

Realistically developed theoretical models of human joints play a significant role in understanding both normal and abnormal joint functions, as well as improving biodynamic response of multi-segmented total-human-body models. A substantial difficulty in theoretical modeling of human joints arises from the fact that the number of unknowns are usually far greater than the number of available equilibrium or dynamic equations. Thus, the problem is an indeterminate one. To deal with this indeterminate situation, optimization techniques have been employed in the past (1,2). However, the selection of objective functions appears to be arbitrary, and justification for such minimization criteria is indeed debatable. Another technique dealing with the indeterminate nature of the joint modeling considers the anatomical and physiological constraint conditions together with the equilibrium or dynamic equations. These constraint conditions include the fact that soft tissues only transmit tensile loads while the articulating surfaces can only be subjected to compression. Electromyographic data from the muscles crossing the joint also provide additional information for the joint modeling effort. The different techniques used by various researchers mainly vary on the method of applying these conditions. At one extreme all unknowns are included in the equilibrium or dynamic equations.