A powered prosthesis with serial and/or parallel compliance, comprises a lower member (12) and an upper member (13), connected via a rotary joint (30), further comprising an actuator (20) connected with the lower member (12) and the upper member (13) to impart rotary motion to said lower member (12) and upper member (13) and a spring (25) connected with the actuator (20). The spring (25) is connected with actuator (20) in parallel and is attached between the lower member (12) and the upper member (13) at predetermined attachment points (23, 24) adapted that the force exerted by the parallel spring (25) supports the actuator in extension for a flexion angle between the lower member (12) and the upper member (13) between 20 and 90 degrees.
