Abstract: A four leg, lower extremity, robotic exoskeleton system is provided for medically assistive motion in gait, sit to stand (STS) and step climbing activities. The system has four articulated robotic legs, including two exoskeleton legs and two auto-pole legs, which are connected to a torso frame, controlled by a motion controller and a user interfaces, and that interacts with an assistive stationary robotic chair, or a wheelchair, for storage, dressing, STS and rest. The STS motion, in the stationary chair and the wheelchair, may be done with a single axis linear actuator, which maintains a back seat tip parallel to the ground for safety and comfort. Links of the exoskeleton and auto-pole legs are actuated by a linear or rotary actuators with their synchronized motion controlled by the motion controller, for safety, comfort and cost performance optimization depending on the medical needs.