Patent ID: 7470289

Claim:
A knee joint endoprosthesis, comprising: a tibial component having an anchor portion ( 5 ) and a tray ( 4 ) on an upper end of the anchor portion adapted to be fixed to bone; a femoral component adapted to be fixed to bone; a polyethylene plate ( 1 ) having an attachment ( 2 ) formed as a unit with the plate ( 1 ); the polyethylene plate ( 1 ) and attachment ( 2 ) made to consist of a polyethylene of ultrahigh molecular weight and/or a cross-linked polyethylene; wherein the plate ( 1 ) is located between the femoral component and tibial component so that the femoral component rests and articulates on the polyethylene plate ( 1 ) by curved surfaces; wherein the anchor portion ( 5 ) has a recess ( 7 ) having a non-circular cross-sectional shape spaced apart below the tray ( 4 ); wherein said attachment ( 2 ) extends down inside the anchor portion ( 5 ) of the tibial component; wherein a free end portion ( 3 ) of the attachment ( 2 ) is non-rotatably fixed by an outer contour on the free end portion ( 3 ) of the attachment ( 2 ) that corresponds to and engages in the non-circular recess ( 7 ) of the anchor portion ( 5 ) to provide a positive fit that precludes rotation of the free end portion ( 3 ) in the recess ( 7 ); and wherein the positive fit results in avoidance of local peak loads and high polyethylene wear.