Disposable modular spacer device (1) of the articulation of a knee comprising a tibial element (2, 2', 2' ' ), constrainable to an end of the tibial bone in proximity of the articulation of the knee and comprising a lower surface (7) and an upper surface (16, 16', 16'') provided with a radius of curvature R2, and a femoral element (4, 4', 4''), comprising an inner surface (14), constrainable to an end of the femoral bone at the articulation of the knee and an outer convex surface (15, 15', 15''), provided with a radius of curvature R1 and in contact with the upper surface (16, 16', 16'') of the tibial element (2, 2', 2''), the tibial element (2, 2', 2") and the femoral element (4, 4', 4'') having various dimensions or sizes, the tibial element (2, 2', 2'') being configured so as to be coupled with any size of the femoral element (4, 4', 4'') to adapt the dimensions of the modular spacer device (1) with the dimensions of the bone ends to which it should be connected.