This paper deals with increasing of the quality of knee prosthesis friction surfaces, in order to reduce wear debris production. Before manufacturing, data file format exchange often generates geometrical discontinuities which lead to imperfections on machined surfaces. A new five degree polynomial interpolation method has therefore been developed to limit such defect. A Design of Experiment has then been carried out to optimize the discretisation intervals of the CAD/CAM model and to test the capacity of this new strategy to smooth undesired typical geometrical discontinuities. The method is also compared to standard techniques. The results show a significant improvement of the surface quality provided by the new polynomial interpolation.