This paper describes a wearable powered leg orthosis that includes a high-torque actuator, electronics, sensors, and embedded firmware. The device provides multiple modes of operation including automatic assistance, manual assistance, continuous passive motion and robotic therapy. Patients affected by neurological conditions including stroke, MS, and Parkinson's disease may benefit from robotic therapy and from the improved mobility provided by this portable, lightweight device. A preliminary study of chronic stroke patients has shown retained improvement in walking speed for patients undergoing rehabilitation with the device.