Abstract
Today's most basic and important total knee replacement design concepts arose out of an earlier era in which 2 distinct approaches emerged, functional and anatomic. Functional approaches simplified knee kinetics, were easier to implant, and gained widespread popularity, in part, from their inventory control. Anatomic approaches were an attempt to recreate normal knee motion with low prosthetic contact stress. Historically, however, they became impractical to produce because of the cost of maintaining a wide variety of anatomic knee implants. New customized designs may return the anatomic design to favor due to several key features that borrow anatomic principles developed in the past, and improved with new ideas.