This paper addresses the working principal of a sitting/lying type passive lower limb rehabilitation robot (LLRR) where patients legs are connected with a passive serial manipulator(orthoses) which consists of three rotary joints serially connected in a plane (RRR), with an active feedback, driven by a three degrees of freedom (DOF) parallel manipulator looks like a symbol The Lambda. The kinematics of the proposed rehabilitation robot has been presented and discussed. Performance analysis of the proposed robot for basic therapeutic exercises has been analyzed on a virtual prototype with the help of multibody dynamic package (namely MSC ADAMS™) and discussed. © 2015, Indian Institute of Technology, IIT. All rights reserved.