This paper addresses a 2PRP-2PPR planar parallel manipulator and, its implementation in the design and development of a new lower limb rehabilitation robot (LLRR). The difficulty and limitation of the existing mechanisms has been analysed and a new mechanism is proposed. Some limitation of the proposed manipulator, namely limited effective workspace, has also been overcome by gear arrangement to make it suitable for the application. The proposed mechanism is able to perform like a serial LLRR with the same clinical space with advantages of parallel manipulators like better accuracy, speed and stiffness. The proposed manipulator consist of a vertical planar parallel manipulator (2PRP-2PPR)which is driver mechanism and a lower limb orthosis which is driven and actuator-free mechanism has a RRR serial planar configuration, is designed to treat the patient in sitting/lying postures. Validation of the functional design and working of the proposed system has been done analytically by using the clinical gait pattern data. © Springer International Publishing Switzerland 2017.