Many transfemoral amputees in low-income nations were unable to obtain a much-needed prosthesis. As a result, in recent years, cheap semi-active artificial knees have been developed. Because the swing portion of the gait cycle is more unstable than the stance phase, those designs couldn't fully match a healthy human's swing phase. The design of a magnetorheological (MR) damper is based on the swing-phase trajectory of an above-knee prosthesis where damping affecting is predominant in this study. A swing phase model of the intended single axis knee with MR damper is created first. The dynamic properties of the damper are represented using a parametric model. According to testing data, the damper settings that determine damping force of the damper are found and tuned to allow the artificial knee to create a near-normal swing phase trajectory for level-ground walking. The design of an MR damper valve that is physically confined in a desired cylindrical volume is designed based on the ideal damper parameters, and its performance is tested for the intended application. The damper's ideal construction is also proposed. The results reveal that the developed MR damper outperforms off-the-shelf MR dampers for the application, with a weight reduction of up to 70.4 percent.