The use of nanoparticles for nano-magnetorheological fluids (NMRFs)  preparation has become attractive in various potential applications because of its magneto-mechanical properties. From this point of view, the NiFe2O4 nanoparticles synthesized using the gel burning technique was used for NMRF preparation and characterization. The oscillatory strain sweep testing at an applied magnetic field range of 0–1.191 T under steady state flow conditions with an optimal particle concentration the maximum shear stress was achieved. It was apparent that the shear stress increased according to the applied field. The design and performance of the damper application devices are significantly influenced by the fluid properties of the MR damper. First, the design features of the MR damper are presented and the detailed finite element analysis is studied. This magneto smart material has created its claims in biomedical field, especially in prosthetics. This chapter presents the performance of NMRF damper, design and analysis for prototype leg prosthetics with an active damping for people who undergo amputations in their limbs especially when used in legs. The fluid change is directly relative to the magnetic field applied, which is the main aspect of anatomy and biomechanics of the foot-leg system. The force applied while walking in the progression of the cyclic form movement is absorbed by the prosthetics, thereby decreasing the impact on amputee’s support under different load conditions.