Abstract: Anchoring device for a knee prosthesis of the unicompartmental or bicompartmental type, the said prosthesis comprising a tibial plateau provided on its tibial bearing face with anchoring grooves of dovetailed profile forming a grid pattern, characterized in that the anchoring is achieved by an anchoring crosspiece (7) inserted in the tibia and provided on its upper face with a stud (6) complementary to the groove forming a notch and engaging in the latter.