Recently, two major orthopaedic implant manufacturers, (Stryker Corp. and Zimmer Holdings Inc.) announced the availability of total knee replacement implants specifically designed for women. We all know that men and women are different, but how does this relate to knee implants?

The key difference is the relative size of the end of the femur or thigh bone. For a given front-to-back or anterior-posterior (AP) width, the femurs of females tend to be narrower in the medial-lateral (ML) or side-to-side direction compared to males. An implant which is proportioned based on male anatomy would, therefore, be too wide on a similarly sized female. The result is that when a surgeon sizes the implant based on the AP width of the femur, the implant could