A facet joint prosthesis for replacing a facet joint comprising superior and inferior facets, the prosthesis comprising:a) a superior facet joint component forming a superior endplate having a superior outer surface adapted to attach to the superior facet and an inner surface,b) an inferior facet joint component forming an inferior endplate having an inferior outer surface adapted to attach to the inferior facet and an inner surface, andc) a ligament adapted to constrain relative movement between the facets,wherein the ligament comprises an elastic core having a superior surface adapted to attach to the inner surface of the superior facet joint component and an inferior surface adapted to attach to the inner surface of the inferior facet joint component.
