A model of the human knee, derived from kinematic principles and its relevance for endoprosthesis design.

A mainly deductive kinematic model of the human knee is described. The modelling procedure is based upon the application of a four-bar mechanism. Emphasis has been laid upon elucidating the functional anatomical relationship between several morphological characteristics concerning the shape of the articular surfaces and the constellation of the cruciate ligaments. Starting from a simple planar model, which simulates motions in a sagittal plane only, a spatial model was developed, which allowed an additional longitudinal rotation of the tibia also. The conclusions drawn from this modelling procedure have been used to evaluate from an functional anatomical point of view the current designs of presently available endoprostheses for the knee.