Abstract— This study presents the results of an investigation of Magnetorheological fluids used in the implementation of a knee prosthesis prototype with active movement control and stability in posture, when replacing lost muscle function for people with transfemoral amputations. A magnetorheological torque limiter was used to implement a prosthetic knee device with adjustable torque applied to the join. This was achieved by using a magnetorheological fluid (MRF) brake lord MRF – 140 CG as actuator. This prosthesis includes rotation lock, an impact attenuator to simulate the natural action of normal knee flexion, and torque regulation to provide maximum safety and a normal walking movement. The prototype has a control for the adjustment of the magnetic field applied to the MRF, thus successfully emulating human march of the prosthesis in different positions. 