| abstract |
A mobile bearing knee prosthesis in which the tibial component includes an upstanding post and a cap provided at an upper end thereof. The cap includes a lip extending laterally outward from the post to give the cap a generally oval shape with a major axis in the A/P direction and a minor axis in the M/L direction. The meniscal insert includes an undercut cavity elongated in the A/P direction in which the post is received. The undercut cavity has a length allowing substantial movement of the post therealong in the A/P direction, and a width allowing only a minor movement of the post in the M/L direction. The insert also includes an upper cutout extending around an upper portion of the cavity which receives therein an adjacent portion of the lip. With this construction, the insert and the baseplate are free to slide relative to one another along a plane of contact therebetween, except when constrained by (i) a contact of the post with the undercut cavity as movement occurs in the A/P and M/L directions, whereby substantial relative movement of the insert and baseplate in the A/P direction is allowed and only a minor relative movement in the M/L direction is allowed, and (ii) an engagement of the lip located between the minor axis and the major axis with the upper cutout as rotation occurs about an axis perpendicular to the plane of contact, whereby only some predetermined rotational relative movement is allowed. |