The knee prosthesis with rotary plate comprises a metal base (2) and a tibia plate (3) which are equipped with guide means (22, 22', 22'', 26, 29, 5, 6, 5', 9, 50, 51, 52, 13, 15, 18; 34, 34', 34'', 35, 37, 7, 8, 10, 12, 53, 54, 55, 10', 17) defining a center of rotation (C, C') which may be offset from that of the tibia bone axis (YY'), so as to allow the tibia plate (3) to slide in rotation over the said base, the said guide means being positioned a certain distance away from the center of rotation (C, C').