This work entitled "design of a semi-automatic mechanical system to perform physiotherapy exercises for the knee", it was developed using the genetic algorithms method, for the design of the four-bar mechanism. First the dimensions of the lower extremities were found for a person of 1.60 m, for which the book of anthropometric dimensions of the Latin American population and the model of the segments of the human body as a function of height were taken as a reference, based on This information was graphed in the GeoGebra software, and then simulated to obtain the 6 knee positions in flexion and extension in the four-bar mechanism. With the method of optimization of synthesis by genetic algorithm, applied to the generation of movement for six positions of a mechanism of four bars, it was achieved thanks to the Matlab program for it was generated a population of 1000 individuals randomly an...