Little attention has been devoted to enabling Robot assisted gait rehabilitation of locomotion disorders from orthopedic origin. This paper proposes a weight support system for gait rehabilitation research in clinical environments that includes a novel pelvic support attached to a Cartesian assistive manipulator. Such an actuation configuration allows studying the patient's ambulation when wearing supporting devices. A basic dynamic model and control is done for testing system functionality. Preliminary experiments in weight-bearing walking are presented. The results showed the electrical and software architecture provided a stable platform for controlling the actuation mechanisms. Load relieve accompanied of full joint motion indicates the suitability of the proposed system for rehabilitation of locomotion disorders from orthopedic origin.