Associated Press
In this photo taken Aug. 5, 2011, Dr. Kirt Kimball displays two models demonstrating two traditional knee replacement surgeries at his office at Timpanogos Regional Medical Center in Orem, Utah. Kimball recently performed an innovative total knee replacement surgery that removes less bone material than current total knee replacement surgeries, preserves existing tendons, and utilizes components specific to the patient. Kimball believes this new procedure is more efficient than previous methods. (AP Photo/Daily Herald, James Roh)

PROVO — Sonia Peterson has been afraid to pick up her grandchildren for months.

She's only 51, but her right knee was so weak and painful that she never knew when it was going to give and dump her on the ground.

The pain eventually led her to seek total knee replacement, even though a metal-and-plastic joint was never going to be as good as the real thing.

Peterson, however, was a good candidate for a new knee replacement technology — a knee made just for her. Instead of picking one of a handful of generic replacement joints that best fit her knee, Dr. Kirt Kimball put in an artificial knee made just for Peterson, using tools made for that specific surgery. On Aug. 4, she became the first recipient in Utah and one of the first in the nation for this new knee surgery.

"I didn't want to give up my high heels, and he said, 'You don't have to,' " Peterson said.

Kimball, an orthopedic surgeon with Central Utah Clinic, is one of 10 U.S. doctors who trained with this technology, which was produced by Conformis, a company that specializes in individual implants. The Food and Drug Administration approved it several months ago, and so far, so good.

Knee replacements traditionally have been done as one-size-fits-all, with the same dozens of tools and half-dozen possible replacements sitting on a table during surgery. The surgeon has to figure out which implant fits best and then fit the knee to it, which usually means sawing off bone and cutting usable ligaments.

With this technology, the patient gets a CT scan, which is sent to Conformis, which builds a knee specifically for that joint. Because it was made to fit the knee instead of the other way around, the surgeon doesn't have to scrap the patient's ligaments and saw off large chunks of bone. That should make healing more quick and complete. Kimball said he tested Peterson after the replacement was in, and her knee seemed tighter and more responsive, more like a healthy real knee than with previous implants on other patients.

"My feeling is that this will change the entire industry," he said.

That industry is a big one. About 500,000 people a year get knee replacements; Kimball said that number will jump into the millions as the baby boomers get older. There are a lot of causes for bad knees among people as young as Peterson to people in their 80s.

"At the end of the day, it's a painful, worn-out knee," Kimball said.

Many surgeons do a few knee replacements a year, but it's not their primary practice. New technology needs to be simple and defined enough that those surgeons who do knee replacements only once or twice a month can shift quickly.

Because this type of knee implant is so new, many questions have yet to be answered. It might last 20 years or more; it might not. The tools still are being refined. Recovery might not be any easier than a regular replacement.

But for now, for Sonia Peterson, she's thrilled. Within 24 hours of her surgery, she'd gotten up. She anticipated returning to gardening, playing on the floor and return to the life she knew before the knee pain started ruling her days.

"Now that I've had it replaced, I need to get all the mileage that I can out of it," she said.