Abstract: An orthotic or prosthetic actuator is provided which includes a parallel eccentric gear train which terminates on a first end in a first plate, and which terminates on a second end in a second, rotatable plate which is adjacent to the first plate. The actuator further includes a spring which is disposed between these adjacent plates. The actuator preferably utilizes Oldham coupling, by way of a pair of crosslinks disposed on each side of the motor, to restrain rotation of the dual parallel eccentric gears in the actuator, while permitting their linear oscillation. The crosslinks are preferably equipped with a tongue/spline lubrication system to provide continuous lubrication to the mated and loaded crosslink tongue and groove surfaces.