This paper proposes a planar hybrid manipulator system integrated with a passive serial orthosis for a foot-plate based sitting-type lower limb rehabilitation robot. The proposed robotic system has a modularity which can be easily upgraded to a standing-type body weight support (BWS) mechanism. The detailed design and development of the robot are discussed in this paper along with its kinematic and dynamic analyses. The rehabilitation strategy is described for the field of application. The effectiveness and performance of the proposed mechanism are demonstrated with a clinical gait pattern using a proportional-integral-derivative (PID) control scheme on an in-house fabricated real-time prototype. The prototype experiments are conducted in view of validating the prototype for the therapeutic and gait training motions. © 2017 Elsevier Ltd