In knee prostheses, the curve of the instantaneous center of rotation (ICR) and, therefore, stability of the prothesis are the most important parameters to be considered. The ICR curve depends on many parameters. One of them and the most effective one is the dimensions of four bar mechanism. In polycentric knee mechanisms, it has become inevitable to use optimization techniques while determining the dimensions of the mechanism for the stability of the prosthesis in the stance position. In this study, definitions of knee prostheses and polycentric knee mechanisms are given, optimization studies written in this field are mentioned thorough literature research. The study aims to find mechanism dimensions that gives ICR curve close to the reference curve by optimizing the mechanism dimensions of four-bar knee mechanisms. The Bees Algorithm and Genetic Algorithm (GA) were used for this purpose. The limits and objective function for the optimization were determined, and after many trials, separate mechanism dimensions with The Bees Algorithm and the Genetic Algorithm are obtained. By comparing the results, it has been observed that the dimensions obtained by The Bees Algorithm produced a better approximation to the reference instantaneous center of rotation curve.