A knee designed just for a woman

Anne Tate's son has a theory about her knees: One will walk like a cowboy, the other like a go-go dancer.

In September, Tate became something of an experiment when she had her right knee replaced with a new implant designed specifically for women.

Last year, Tate, of Chesapeake said she had her left knee done with the traditional implant that seems to fit men better than women.

"It may be all in my head but it seems like this knee bends more readily," Tate, 77, said of her so-called "feminine knee."

The gender-specific implant, which was approved by the federal Food and Drug Administration in the spring, is one of the latest signs that the medical community is recognizing that men and women are different in more than just the obvious ways.

Traditionally, the assumption was that if it worked for a man, it would work for a woman. U ntil a bout a decade ago, many medical research trials focused exclusively on male subjects. The results were then extrapolated to women.

Women were receiving "inferior health care simply because there was no data on women," said Sherry Marts, vice president for scientific affairs for the Society for Women's Health Research, a nonprofit organization in Washington.

Not recognizing gender differences can have profound health consequences. For example, the "classic" symptom of a heart attack - crushing chest pain - is really only typical of men, Marts said. Women having heart attacks are more likely to feel nauseated, extremely fatigued and short of breath - and more likely to have their symptoms misdiagnosed.

While progress has been made, there's still a long way to go to raise awareness of sex differences, Marts said. That it's 2006 and a knee implant designed for women - who make up about two-thirds of knee-replacement surgeries - is "new" might be a sign of that.

"I'm enthusiastic that the industry is at least acknowledging that men's and women's joints are shaped differently," Marts said.

Nationwide, between 1995 and 2004, the rate of knee replacements in those 65 and older has gone up from 47.2 per 10,000 patients to 80.3 per 10,000, according to the Centers for Disease Control and Prevention. In 2004, the latest year for which figures are available, 311,000 women had total knee replacements, versus 167,000 men.

The greater number of women having the surgery may be due in part to their higher rates of osteoarthritis. That's what put Bessie Greenhouse of Chesapeake in a wheelchair a few years ago after years of suffering from severe pain and knee instability.

Last year, Greenhouse's right knee was replaced using the standard implant. That knee was in worse shape, but Greenhouse, 72, said she could tell that the left was not far behind.

"It was going to give out eventually," she said.

On Oct. 5, Dr. Michael Romash replaced Greenhouse's left knee, this time using the gender-specific implant.

Greenhouse and Romash said that the chance for a better fit and improved mobility led him to use the new implant. While the traditional implants come in many sizes, they tend to be a little too thick on top of a woman's knee and a little too wide on the side, and the kneecap tracks at a slightly different angle.

Romash said the surgical technique - he uses a small incision to spare the muscles and tendons - is the same as the standard implant.

While he was operating on Greenhouse, the sound of saws and drills filling the air, Romash explained that he was making sure the knee was fitting "side to side, front to back, and I have to line it up twisty-wise."

"The inherent fit of the thing was quite excellent," Romash said near the end of the surgery.

During physical therapy Friday, eight days after surgery, Greenhouse was bending her knee and going up and down a few stairs.

Greenhouse, who was happy with the first knee replacement - which freed her from the wheelchair and left her with no pain in that knee - said she was still glad to hear that her left knee had the gender-specific implant.

"I thought it was good," Greenhouse said. "We should have our own joints."

As for Tate, she's not walking like either a cowboy or a go-go dancer - but she is looking forward to getting back to the pool at the YMCA and walking without a cane at her granddaughter's wedding in August.

"And if some nice guy asks me to dance," she said, "I can take him up on it."