This paper proposes a kinematically redundant planar manipulator for lower limb rehabilitation application, having configuration 4PRP. The challenges in the existing mechanisms has been analyzed and a new configuration is proposed. This configuration helps to improve the effective workspace of the lower limb rehabilitation robot. The lower limb rehabilitation systems are used to treat the post stroke patients and limb injured patients by providing rigorous exercises through the motor nerves recovery. This paper shows the advantages of the proposed 4-PRP kinematically redundant planar manipulator over existing 2PRP-2PPR in providing higher effective workspace with same capability in performing lower limb rehabilitation tasks. © Springer Nature Singapore Pte Ltd. 2016.