Patent ID: 8142510

Claim:
A mobile tibial assembly comprising: a tibial tray configured to be coupled to a surgically-prepared surface of the proximal end of a tibia, the tibial tray having (i) an upper surface, (ii) a bottom surface, the bottom surface being configured to contact a portion of the surgically-prepared surface of the tibia when coupled thereto, and (iii) a track defined in the upper surface having a bottom wall that is flat in the medial-lateral direction and convex in the anterior-posterior direction; and a tibial insert having an (i) upper bearing surface and (ii) a bottom bearing surface configured to contact the upper surface of the tibial tray when the tibial insert is coupled to the tibial tray, the bottom bearing surface having a surface area, and (iii) a stem including a circular neck connected to the bottom bearing surface and a circular flange extending from a distal end of the circular neck, the circular neck having a first diameter and a cross-sectional area that is less than the surface area of the bottom bearing surface, the circular flange having a second diameter greater than the first diameter of the circular neck, the stem being received by the track of the tibial tray, wherein (i) the tibial insert is movable along the track relative to the tibial tray, (ii) the upper surface of the tibial tray is convex and the bottom bearing surface of the tibial insert is concave such that the convex upper surface of the tibial tray contacts the concave bottom bearing surface of the tibial insert as the tibial insert is moved along the track relative to the tibial tray in a generally anterior-posterior direction, and (iii) the tibial insert is freely rotatable about a central axis defined by the stem as the tibial insert is moved along the track relative to the tibial tray in the generally anterior-posterior direction.