A three-dimensional multivariate model of passive human joint torques and articular boundaries

Objective. The development of a novel three-dimensional mathematical model of passive human joint torques that is of practical use, takes into account the complex non-linear interactions that exist between the moments generated by the various passive structures spanning the joint in question, and is applicable to all types of articular joints. Design. Mathematical model validated by practical implementation, Background. Previous models of passive human joint torques were predominantly one-dimensional and did not take into account the interactions of the various structural components, Methods. Mathematical modelling is used in conjunction with repeated passive torque experiments on the right elbow joint of a healthy 29-year-old male, On the basis of the experimentally observed torque-angle data, the full set of articular model parameters characterizing the two-dimensional passive elastic torque function of the subject's right elbow joint could be determined. Results. In addition to the passive elastic torque functions, the two-dimensional contour of the elbow joint's articular boundaries was also obtained. Conclusions. The present model is especially useful for assessing certain pathological conditions in any body joint investigated, and in addition is best suited for the inclusion in large-scale dynamic simulation models of the human neuromusculoskeletal system. Relevance Both the contour of a joint's articular boundaries and the diagrams of its passive elastic moment functions as computed by the present model can be used as clinical indicators for possibly abnormal and impaired joint mobility. (C) Elsevier Science Ltd.