A single-compartment knee prosthesis provides different femoral implants for the medial and lateral compartments. Both femoral implants feature distinct bends and slight twists following the anatomical shape of the corresponding compartment, of about 22.degree. for the medial implant (11) and 14.degree. for the lateral femoral implant (31). The complementary tibial plates also differ according to whether they are adapted to the medial or to the lateral compartment. In the latter case, the shape of the tibial plate (39) is substantially semicircular whereas the medial tibial plate (19) is more elongated.