Tibia platform for a knee joint prosthesis and knee joint prosthesis with such a tibia platform

The tibia platform (1) contains a joint support (5) and an anchoring part (4) with passage openings (12) for fastening elements (14) for fastening the anchoring part (4) to the tibia bone (3). The passage openings (12) are each executed with a femur-side, upper countersink (25). At least one passage opening (12) not used for the fastening is provided with a closure plug (15) which can be inserted from above, which is executed with a supporting surface (16a) running around this sealing surface (16a) and can be braced in the countersink (25). The closure plug (15) contains a number of spring tongues (18) which can be introduced into the relevant passage opening (12) and which form a snap connection with the wall of the passage opening (12), and a central cylindrical protusion (17) which is provided with a blind bore (17a) open upwards for receiving a setting tool (20). In this manner a secure sealing of the passage opening (12) is attained and the movement into the tibia bone bed of abraded particles possibly originating between the anchoring part (4) and the joint support (5) is prevented.