Marlene Freed knows what's coming. For 10 relaxing minutes, she has been lying on her back, with ice chilling the swollen tissue around a seven-inch scar on her right leg -- the spot where doctors inserted her new titanium knee.
The 68-year-old Olney resident is laughing and chatting. But when physical therapist Chris Gnip climbs onto the table and starts to bend her knee, pushing it carefully but relentlessly toward her chest, Freed clams up.
She closes her eyes and starts to breathe deeply. Her hand clutches the plastic cushion on the office table. The more Gnip pushes that knee, the more the pain shows on Freed's face.
"OK," she mutters, and Gnip holds the knee in place.
"Five, four, three, two, one," he counts down. And finally lets go of the knee.
"So they know when the end is," he explains.
Freed has plenty of company in rehab these days. In 2003, the last year for which figures are available, doctors replaced more than 400,000 knees in the United States, two-thirds of them in women, according to the National Center for Health Statistics.
One reason for the continuing increase is that more active baby boomers are having knees replaced -- and doing it earlier than their predecessors. Women are also having more successful replacements than they used to -- and some credit a generation of new artificial knees designed just for them.
That happy knowledge does not necessarily make it easier for Freed, who had her left knee replaced in June and the right one replaced Jan. 9.
For an hour, Gnip puts her through her paces in the Clarksville offices of Physiotherapy Associates: leg raises, knee bends, quadriceps stretches.
"This is another fun one," Freed says, rolling her eyes and sliding her foot down the wall, bending the knee on her own while supporting it with her left foot. By this time she is breathing hard and is pink in the face.
"You're doing well," Gnip says.
Freed just chuckles. "You start out and you don't think it'll ever change," she says.
For Freed and others who wind up with replacement surgery, arthritis, injuries or the wear and tear of life have caused their knee cartilage to degenerate.
When the tissue that cushions the bones in the knee wears out, the upper and lower leg bones begin to grind together, causing pain and swelling.
When patients can no longer put up with the pain, and other treatments such as cortisone shots and arthroscopic surgery have failed, knee replacements are increasingly more popular options.
Freed decided to get the first one in May, when she traveled to Turkey and met two women her age who had already had double replacements. "Then," she said, "when I realized how much I could do with this new knee, I decided to get a matching one."
Among those 65 and older, the U.S. Centers for Disease Control and Prevention estimates that the rate of knee replacement increased eightfold between 1979 and 2002.
A 2006 study by the American Academy of Orthopaedic Surgeons predicts an astonishing 673 percent increase in the number of knee replacements during the next 23 years, with 3.5 million artificial knees implanted annually by the year 2030.
Obesity and a generation of baby boomers "wanting to stay more active" are the two main reasons for the most recent increase, explains Annie Hayashi, media relations manager for the surgeons' group.
Additionally, more people are getting their new knees earlier in life, says Dr. Kamala Littleton, the director of the Orthopedic Program for Women at Mercy Medical Center.
"We would wait, in effect putting Band-aids on the problem, until they were 65," Littleton said. "Surgeons were hesitant to perform surgery on younger people, trying to avoid more complicated revision surgery when the implants wore out.
"Now we're seeing 86 percent of knee implants still functioning well at 15 years. Essentially by waiting, we were making this person live a life of someone 20 years older. You don't want somebody who's 52 hobbling around, needing a cane, who can't play with their children or grandchildren, who can't enjoy activities such as golf or bowling or even just walking.
That's what happened to Marti Startt, 62, who tried arthroscopic surgery on her right knee to repair an old running injury that had developed into degenerative arthritis. It didn't help much.
"Stairs were hellacious," she said, forcing her to sell her third-floor walk-up and buy a condominium in a building with an elevator.
On Jan. 15, the Columbia resident had replacement surgery. Now she's working aggressively on rehab. "I just want to get back to normal life," she says.
The knee replacement operation, first performed in 1968, sounds as much like furniture repair as it does medicine.
The bits of bone and cartilage, damaged by injury or arthritis or both, are cut away. A shiny new metal saucer, shaped like the bottom of the femur, is spiked into the thighbone.
A shiny new saucer, shaped like the top of the tibia, is spiked into the tibia bone. A high-tech plastic insert is sandwiched between them, and a disc of plastic is glued on the back of the kneecap to make sure everything slides together easily. Viola -- a new knee.
The surgery typically takes two hours and cost about $30,000 in 2003, the last year for which figures were available. That includes three to five days in the hospital afterward, according to the AAOS.
The latest developments involve implants designed for and marketed to women. They're designed more like a woman's real knee, with angles and bone shapes that are somewhat different from men's.
There's even intense competition in the market -- backed by heavy advertising -- between models such as Stryker's 2004 Triathlon knee, Zimmer's Gender Solution for women and DePuy Orthopaedics' "rolling platform" knee.
DePuy, a Johnson & Johnson subsidiary whose ad campaign enlisted 82-year-old actress Angela Lansbury, says its design better allows for women's natural knee rotation.
Gender-specific knees are "a great idea," says Mercy's Littleton. "It allows us to customize more to each patient. Although data is not available to show it to be superior, it gives us the ability to better replicate a woman's anatomy."
When Littleton replaces a knee, she chooses the best fit from a variety of prosthetic joints -- regular or female.
Women's thigh bones are slimmer than men's, and if the new knee is cut slimmer, then "you'll have less over-stuffing of the joint, with more range of motion. ... When you're trying to replicate a person's anatomy, it gives you the option of replicating it better," she says.
This is still a controversial notion -- some surgeons reject gender-specific implants altogether. Others are intrigued by the idea but haven't tried it.
Dr. Kimberly Templeton, an associate professor at the University of Kansas Medical Center and chief of orthopedic surgery at the Kansas City VA Medical Center, is one of them.
"Some surgeons tend to be conservative," she said, and most like using devices they're used to. Still, Templeton says she performs 50 to 100 knee replacements a year and is becoming convinced that the new gender-specific models make sense.
"Bones and joints are different in men and women; the hormones cause different responses," she says.
Women are more likely to have knee problems than men, for a combination of reasons, she says. They tend to develop osteoarthritis more often because of sports injuries, obesity and living longer. Recent studies also show that as estrogen decreases in aging women, cartilage breaks down more easily.
Moreover, studies have long shown that women have fared worse than men after knee replacements, Templeton says.
"Maybe the implants weren't fitting as well -- maybe it's because the cut of the bones, the size and the orientation are different in men than in women. But the other factor is that women get knee replacements later, and if you're more debilitated to start with, your outcome won't be as good," she says,
Her solution: women need knee replacements earlier in life.
"We need to have a campaign to let women and their families know that knee replacement is OK," Templeton say. "It can keep [women] healthier and out more."
All sides agree that once the surgery is done, the key to recovery is physical therapy. Many patients are pulled to their feet to try a cane or walker on the day of the operation.
Two weeks after the operation, patients should be able to bend their new knee to a 90-degree angle, so they can go downstairs and sit down by themselves, said Megan Greco, clinic director at Physiotherapy Associates.
"By the end of the second week, we have them in outpatient, working on range of motion," Greco said.
How bad is the pain?
"It does hurt," Greco says. "They absolutely hate it when we say, 'OK, let's push it.' And you have to do the exercises at home. We can tell when you're not."
But with eight to 10 weeks of therapy, most patients do well -- and are in less pain than they were before the operation.
Jeannette Roman of Columbia remembers her surgery well. "Sept. 24, 1998," she recalls. It was at Kernan Hospital in Baltimore, when she was 80.
"It was wonderful," Roman says, "because I was in a lot of pain. I had a lot of swelling. I couldn't walk or anything. After the surgery, it felt great."
Although she's slowed down a bit now that she's nearly 90, she says she's still walking to the grocery store.
Freed is hoping for that kind of recovery. She wants to get back to camping and hiking and biking the roads around her beach house in Lewes, Del. Mostly, Freed wants to get back to traveling. She has trips planned for Alaska in June and Copper Canyon, Mexico, in the fall.
And in 2009? A trip out West with her grandchildren.
"Or maybe Costa Rica," Freed says, and pedals harder on her stationary bike.
Want to learn more about knee replacement? Go to these Web sites:
National Library of Medicine: medlineplus.gov
American Academy of Orthopaedic Surgeons: aaos.org
Arthritis Foundation: arthritis.org
DePuy Orthopaedics site: kneereplacement.com
Video of surgery from Zimmer: or-live.com/zimmer/1603/event/webcast.clm
Video of surgery from Stryker: stryker.com/ jointreplacement/sites/triathlon