Abstract: A hydraulic apparatus has a cam body rotatable about an axis and with at least two mirror image involute cam surfaces on opposing sides of the axis. Hydraulic actuators on opposing sides of the axis have a linearly extendable ram and a hydraulic cylinder. A fluid supply line is provided for delivering a pressurized fluid equally to each of the cylinders. A pressure relief or flow control valve is associated with each of the hydraulic cylinders and is operable to selectively assume a closed position to retain fluid or assume an open position to release fluid from the hydraulic cylinders. A control can operate the pressure relief valves between at least the closed and open positions, to move the rams out of and in to the cylinders to rotate the cam body about the axis with controlled torque. A robotic, prosthetic or orthotic and a method for applying torque to a body are also disclosed.