Knee prosthesis tibial componentry having interchangeable components

Knee prosthesis tibial componentry comprising:

• a bearing insert defining a superior condyle articular surface and a planar inferior bearing surface;
• and
• a tray having a platform defining a superior bearing surface and an inferior stem,
• wherein the tray comprises a quadrant of retention buttresses having anterior and posterior buttresses, each extending superiorly with respect to the superior bearing surface and extending in from a peripheral edge of the superior bearing surface,
• wherein the insert comprises a quadrant of spaced apart retention recesses having anterior and posterior recesses, each recessed superiorly with respect to the inferior bearing surface and extending in from a peripheral edge of the inferior bearing surface,
• wherein the buttresses and recesses define bearing faces that tightly bear against each other in a transverse plane both mediolaterally and anteroposteriorly to retain the insert to the tray,
• wherein the buttresses are spaced apart mediolaterally to allow an anteroposterior channel therebetween across the platform to accommodate a continuous anteroposterior portion of the insert and to allow a posterior bearing surface between the posterior buttresses;
• and
• wherein the buttresses are spaced apart anteroposteriorly to allow a mediolateral channel across the platform to accommodate a continuous mediolateral portion of the insert.