A prosthetic knee joint, comprising: (a) a femoral member comprising a rigid material and having a convex-curved, wear-resistant femoral contact surface, the femoral contact surface including two spaced-apart protruding ridges having a convex cross-sectional shape; and (b) a tibial assembly including: (i) two individual and independently spaced-apart cups, each cup having a body and a peripheral rim extending around an open periphery of the body, wherein the body and rim of each respective cup are formed from a rigid material, the rim having a substantially thicker dimension than the body and defining a wear-resistant cup contact surface, wherein the rim when seen in an elevational view has a saddle-like shape which is lowest in a middle portion from which it, relative to the body, is curved upwards to each of two opposite end portions; (ii) a rigid base; and (iii) two separate spaced-apart spring supports, each spring support independently interconnecting at least part of a respective cup to the base, wherein each spring support is elastically deflectable so as to permit controlled pivoting motion of the respective cup relative to the base; (c) wherein each of the cup contact surfaces receives and bears directly against one of the protruding ridges of the femoral contact surface, so as to transfer axial and lateral loads between the tibial assembly and the femoral member, while allowing pivoting motion between the tibial assembly and the femoral member. (a) a femoral member comprising a rigid material and having a convex-curved, wear-resistant femoral contact surface, the femoral contact surface including two spaced-apart protruding ridges having a convex cross-sectional shape; and (b) a tibial assembly including: (i) two individual and independently spaced-apart cups, each cup having a body and a peripheral rim extending around an open periphery of the body, wherein the body and rim of each respective cup are formed from a rigid material, the rim having a substantially thicker dimension than the body and defining a wear-resistant cup contact surface, wherein the rim when seen in an elevational view has a saddle-like shape which is lowest in a middle portion from which it, relative to the body, is curved upwards to each of two opposite end portions; (ii) a rigid base; and (iii) two separate spaced-apart spring supports, each spring support independently interconnecting at least part of a respective cup to the base, wherein each spring support is elastically deflectable so as to permit controlled pivoting motion of the respective cup relative to the base; (i) two individual and independently spaced-apart cups, each cup having a body and a peripheral rim extending around an open periphery of the body, wherein the body and rim of each respective cup are formed from a rigid material, the rim having a substantially thicker dimension than the body and defining a wear-resistant cup contact surface, wherein the rim when seen in an elevational view has a saddle-like shape which is lowest in a middle portion from which it, relative to the body, is curved upwards to each of two opposite end portions; (ii) a rigid base; and (iii) two separate spaced-apart spring supports, each spring support independently interconnecting at least part of a respective cup to the base, wherein each spring support is elastically deflectable so as to permit controlled pivoting motion of the respective cup relative to the base; (c) wherein each of the cup contact surfaces receives and bears directly against one of the protruding ridges of the femoral contact surface, so as to transfer axial and lateral loads between the tibial assembly and the femoral member, while allowing pivoting motion between the tibial assembly and the femoral member.