I designed and built a novel powered two degree-of-freedom transtibial prosthesis as a test platform for experimentally testing simulation findings of optimal gait with a generic prosthesis model. This design features a non-anthropomorphic anterior-posterior translation axis, allowing the foot to translate forward and backward during walking. This allows the device to control the AP center of pressure location relative to the residual limb, thereby controlling the ground reaction force moment arm against the socket-residuum interface. We found that in simulation, this design reduces peak socket loads while also reducing muscle effort required for walking gait.