Large　displacement　elastic　joints　have　been　widely　used　in　rehabilitation　exoskeleton,　in　this　paper,　a　brief　reminder　of　the　application　of　large　displacement　elastic　joints　in　exoskeleton　robotic　structures　has　been　given.　A　new　concept　of　rigid-compliant　exoskeleton　joint　has　been　presented　using　four-bar　compliant　linkage　for　exoskeleton　robot　applications.　The　paper　describes　the　method　of　designing　the　rigid-compliant　exoskeleton　joint　according　to　the　motion　of　human　knee.