Caring for Hips and Knees to Avoid Artificial Joints

That’s the message of today’s column, which could be headlined Joint Economics.

If you are one of the more than 400,000 people a year who have already had one or more hips or knees replaced — or someone who already has no choice but to consider joining their ranks — we offer our sympathies or encouragement or even congratulations, depending on how you are faring. But this column is for people who are not yet destined to necessarily become part of those statistics.

Although the human body has an amazing capacity to repair itself, our joints are surprisingly fragile.

When the cartilage that cushions bones wears away, it does not grow back. Thinning cartilage contributes to osteoarthritis, also known as degenerative arthritis, a painful and often debilitating condition.

Over time, arthritic joints can become so sore and inflamed that they need to be replaced with mechanical substitutes. A result: more pain, at least in the short term, and big medical bills.

Fortunately, you can act to protect your joints now, to reduce your chances of needing to replace them later.

And protect you should. The cost for a new hip or knee — the joints most commonly replaced — is $30,000 to $40,000. If you have insurance, your total out-of-pocket costs will be much less, but may still be $3,000 to $4,000. And don’t forget to factor in all those days of work you will miss before you get your new prosthetic.

Creaky joints are a growing national problem. The population is getting older, more people are overweight, and an increasing number of children and young adults are playing serious sports and getting seriously injured — all factors that contribute to osteoarthritis.

“Arthritis used to show up in people during their late 40s and 50s, now we’re seeing it earlier, like in the 30s and 40s,” said Dr. Patience White, a rheumatologist and the chief public health officer at the Arthritis Foundation.

The total national bill for hip replacements in 2007 was $19 billion, and $26 billion for knees, according to the federal Agency for Healthcare Research and Quality. Those figures are expected to rise significantly in the coming decade, Dr. White said. So protecting your joints will do more than save wear and tear on you and your budget. You could also be doing your part to curtail the national health care bill.

If your joints are still intact, or just beginning to creak, here are some ways to keep osteoarthritis at bay.

CONTROL YOUR WEIGHT The more you weigh, the more pressure on your joints, which can lead to joint damage. When you walk, each knee bears a force equivalent to three to six times the body’s weight. If you weigh a mere 120 pounds, your knees are taking a 360-pound, or more, beating with every step.

Studies have found a connection between being overweight and developing osteoarthritis of the knees, and to a lesser extent the hips. One recent review found that 27 percent of hip replacements and 69 percent of knee replacements might be attributed to obesity.

For reasons not well understood, weight is more of risk factor for women than men.

“A woman’s risk for developing O.A. is linearly related to her weight,” Dr. David Felson, a rheumatologist and arthritis prevention specialist at Boston University School of Medicine, said, referring to osteoarthritis.

“Men who are moderately overweight are not as at high a risk as a woman of the same weight,” Dr. Felson said.

But a woman can substantially lower her risk by shedding pounds. One study in which Dr. Felson was a co-author found that when a woman lost 10 pounds, her risk of osteoarthritis of the knee dropped by half.

GO LOW-IMPACT Although no definitive link has been found between osteoarthritis of the knee and running (or any other sport), sports medicine doctors discourage their patients from running on hard pavement, playing tennis on concrete or activities like skiing over lots of moguls.

“Impact sports put too much stress on the joints, particularly the knees,” said Dr. Donald M. Kastenbaum vice chairman of orthopedic surgery at Beth Israel Medical Center in Manhattan. “These activities may lead to O.A. and they definitely can escalate the progression of the condition.”

If you run regularly, try to do so on a track or treadmill and consider swapping one run a week for something low-impact like swimming, biking, lifting weights or tai chi.

AVOID INJURY Easier said than done, of course. But major injuries, typically the type that require surgery, greatly increase your risk for osteoarthritis.

According to one big study, 10 to 20 years after a person injures the anterior cruciate ligament or menisci of the knee, that person has a 50 percent chance of having arthritis of the knee.

Those rates are even higher when the injury happens in your 30s or 40s, Dr. Felson said. “As you move into middle age, it’s crucial to avoid sports that predispose you to injury,” he said.

Weekend warriors, who sit at a desk Monday through Friday, and then run or play basketball for five hours straight on the weekend, are at a high risk for injury, and thus for osteoarthritis.

GET FIT It makes sense. The better toned your muscles are, the less likely you are to injure yourself (unless you are also playing football every Saturday morning).

And “building muscles up around joints acts like a shock absorber, spreading stress across the joint,” said Dr. Laith M. Jazrawi, chief of the sports medicine division at NYU Hospital for Joint Diseases. Pilates, moderate weight lifting, vinyasa yoga and swimming are all nonimpact forms of exercise that firm up your muscles without jeopardizing your cartilage.

No definitive link exists between increased flexibility and lower, or higher, rates of osteoarthritis. But some doctors interviewed said they believed that by regularly stretching your muscles you are less likely to injure your joints. It can’t hurt to judiciously stretch your muscles after a workout. And even if it won’t protect your joints from deterioration, it will certainly make your muscles feel better.

BE SKEPTICAL Don’t waste your money on specialized nutrients. Shark cartilage, glucosamine and chondroitin — popular supplements marketed for healthy joints — can be expensive and probably are of limited benefit, many specialists say.

“There’s some evidence to suggest glucosamine and chondroitin sulfate may be helpful in O.A. once it has started, but overall the results are inconclusive,” Dr. Jazrawi said. As for shark cartilage, there is no evidence to suggest that it has any benefit for treating the symptoms or the disease, he said. Joints are like car parts. With proper care and maintenance, they last longer.