Powered gait assistance systems

A powered gait assistance system, comprising:

• a first arm and a second arm coupled together to allow relative pivoting between the first and second arms, wherein the first arm is configured to be coupled to an upper leg portion of a patient and the second arm is configured to be coupled to a lower leg portion of the patient such that relative pivoting between the first and second arms is about an axis proximate the patient's native knee pivot axis;
• a motor coupled to the first and second arms and operable to apply torque between the first and second arms to urge relative pivoting between the first and second arms;
• a torque sensor that measures magnitude of torque applied to the first and second arms;
• an angle sensor that measures a relative angular position between the first and second arms;
• a foot sensor that measures contact of the patient's foot with a ground surface;
• at least one muscle output sensor configured to measure a volitional knee pivoting muscle output;
• and
• a controller programmed to:
• determine a stage of a gait cycle a leg of the patient is in based on signals from one or more of the foot sensor, the angle sensor, and the torque sensor;
• determine a volitional knee pivoting muscle output via one or more muscle output sensors over the course of the gait cycle;
• and
• based on the determined stage of the gait cycle, cause the motor to apply a level of torque between the first and second arms to assist or resist the volitional knee pivoting muscle output during selected stages of the gait cycle, such that the torque applied by the motor improves the patient's leg posture over the gait cycle, wherein the level of torque applied between the first and second arms is based on the volitional knee pivoting muscle output,
• wherein the level of torque between the first and second arms during at least one stage of the gait cycle assists the volitional knee pivoting muscle output to improve the patient's leg posture, and the level of torque applied to the knee joint during at least one other stage of the gait cycle resists the volitional knee pivoting muscle output to increase the strength of at least one targeted muscle over time.