Implants do come in various sizes as well as different shapes and designs. All three are important factors for good knee motion and function.
But it wasn't always this way. In the beginning, there were only a few sizes. And there wasn't any difference between implants used for the right knee versus the left knee.
Over time, researchers helped the manufacturers come up with better designs to fit the anatomy. They found ways to improve how the patella (knee cap) moves up and down over the joint. The implants came with parts that could be sized individually for each patient.
Then in the 1990s, improved materials came out on the market. At the same time, surgeons found better ways to do the surgery. They could use a smaller incision and cut much less of the muscles and soft tissues around the knee.
In the last few years, implant designs have improved for women. Scientists have used CT scans and computer analysis to map out the size, shape, and dimensions of the female knee. This has made it possible to prevent some of the more common problems with implants that are too large or too small.
This same research has also led to improvements for men. We know that a man's knee is more of a rectangular shape than the woman's knee. Shaping the implant to fit the contour of the patient's bone has also helped improve the results.
Your surgeon will take all of these things into consideration when choosing and modifying the right implant for you. But don't hesitate to ask this question. It's always good to feel confident that you are getting exactly what you need.