Disclosed are powered gait assistance systems that include a controller, sensors, and a torque applicator (motor, spring, etc.) coupled to a patient's hips, thighs, knee, lower leg, ankle, and/or foot and operable to apply assistive torque to the patient's leg joint(s) to assist the patient's volitional joint actuating muscle output during selected stages of the patient's gait cycle, such that the applied torque improves the patient's leg posture, muscle output, range of motion, and/or other parameters over the gait cycle. The sensors can include a torque sensor that measures torque applied, one or more joint angle sensors, a ground contact sensor that measures ground contact of the patient's foot, and/or other sensors. The controller can determine what stage of the patient's gait cycle the patient's leg is in based on sensor signals and cause the torque applicator to apply corresponding torque to the joint(s) based on the gait cycle stage, sensor inputs, and known patient characteristics.