Abstract
The frictional factor of new hip endoprosthesis was measured using one hip testing device designed in Biomechanics Laboratory of Medical Bioengineering Faculty. Hip simulator respect physiological condition (variable load, variable motion). The friction factor value for fluid film regime through the gait cycle was founded variable like a consequence of UHMWPE visco-elasto-plastic behaviour. Keywords: friction factor, gait cycle, visco-elasto-plastic behaviour