The "Gender Knee" total knee replacement.
Women are different!
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Knee replacement has improved markedly since first introduced. All manufacturers fo knee replacement prostheses now have multiple models taking into acount the size of the leg bones, right or left etc. Recently a knee replacement has been promoted for women only. Why? Because women are different from men!
If you compare men and women of the same height and leg length there are definite if subtle differences in the anatomy of the knee joints.
The woman's pelvis is wider to allow easier childbirth. The man's pelvis is narrower allowing faster running.
Because the woman's pelvis is wider, the leg bones are angled differently from the man's. The man has a straighter line from anterior superior iliac crest* through the knee cap (patella) to the big toe. *The point you can feel at the top of your pelvis, almost directly across from you umbilicus. The same line in the woman bends inwards to the kneecap and out again to the great toe. The alignment of the woman's knee is more "knock-kneed" than the man's knee alignment.
The kneecap sits differently in the jnee joint. The kneecap is wedge-shaped underneath, the part that meets the knee joint. This wedge-shaped kneecap rides in a V shaped groove in the lower thigh bone (femur) at the knee. In women the groove is shallower and more a "U" than a "V". In men the opposite is true.
Another effect of the different alignment of the leg bones and shape of the patella: The shallower kneecap groove and the different angle of the leg bones make women more likely to suffer from PFPS (Patello Femoral pain Syndrome,) an inflammation of the cartilage under the kneecap. When you squat your patella is pulled to the outside and may rub against the edge of the groove in the femur. In athletes the pull is forceful because of the strength of the thigh muscles. If you watch a University women's volleyball team, you will see that almost all of the women have a brace for this PFPS, but only about one in three of the men in the men's team.
It makes sense to take the differences in alignment and in shape into account when designing a knee replacement.
Studies have not yet been done to compare the gender specific knee replacement to a carefully chosen non-gender specific replacement to see which gives the better result. If no other result has come from the introduction of the gender specific knee replacement, it has made orthopedic surgeons take more care to make sure the optimal fit is achieved.
