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Don't do it for yourself -- but for your knees

September 3, 2008 |  5:59 pm

NewkneesIf your knees are pain-free, enjoy it while you can. Almost half of Americans will develop knee osteoarthritis by the time they're 85, new research suggests.

If the nation keeps packing on the pounds, that number could rise. Extra weight is hard on the knees, which stands to reason considering where those pounds of pressure become focused, substantially increasing the risk that the cartilage protecting the bone will begin to erode. Of course, the aging process takes its own toll. If you're not planning to live to age 85,  presumably you have less to worry about, although you might want to consider the quality of the life you do intend to have.

In the study, researchers at the University of North Carolina, Chapel Hill, and elsewhere collected 13 years of data from more than 3,000 people age 45 and older in Johnston County, N.C., parsing the information and examining participants' knees to assess ultimate risk factors. Gender? Race? Education level? None of those seemed to matter much. Past knee injuries did, though. Folks with those had a 56.8% lifetime risk of developing knee osteoarthritis, compared to 42.3% of those without a former knee injury.

The big factor, however, was weight. Obese people had a 64.5% lifetime risk of the condition, compared to 44.1% for those who were simply overweight and 34.9% of those at normal weight.

The conclusions of the study, the researchers wisely surmise, would hold up far beyond Johnston County as well.

The senior author, Dr. Joanne Jordan, an orthopedics professor at the university, said in a news release that physicians should take special note of the results. "They need to include the risk of knee osteoarthritis in the discussion when counseling patients about weight management and they need to factor that risk into their treatment plans."

Sure, they should. But physicians shouldn't get their hopes up that it will make much difference. If the threat of heart disease and the prospect of extremely uncomfortable flights (I don't care what anyone says, those seats are getting narrower) don't make people change their lifestyle, it seems unlikely that a stern warning about possible knee pain will do it. Perhaps the key would be to emphasize how knee pain can interfere with ... pretty much everything. Everything. 

Then there's the threat of knee replacement surgery. Knee osteoarthritis leads to 418,000 knee replacement procedures annually, according to the Arthritis Foundation's take on the new study.

The American Academy of Orthopaedic Surgeons offers a nifty primer on what's involved, including this nice touch: "Total knee replacement will not make you a super-athlete or allow you to do more than you could before you developed arthritis."

Still think the surgery is no big deal? Check in with someone who's had the operation. The blog Booktoots offers first-person details of total knee replacement surgery along with, among other things, a mystifying love of professional hockey. After the surgery, booktoots teaches us, go-karting is indeed possible. Ultimately, this account, like those of most others who've had the surgery, comes down squarely in the "replacement was worth it in the end" camp.

If you're now at least mildly concerned about developing knee pain and having your life hijacked by it, or of having existing knee pain grow worse, the National Institute of Arthritis and Musculoskeletal and Skin Diseases offers advice for preventing knee problems (specific types of exercises, good shoes) -- as well as what types of exercises are best for people who already have knee pain (range of motion and strengthening activities).

And here's more from the Arthritis Foundation on protecting your joints.

The new study, funded by the Centers for Disease Control and Prevention, was published in the Sept. 15 issue of Arthritis Care & Research.

-- Tami Dennis

Photo: To keep your knees useful, exercise them. And shed the excess weight.

Credit: Stefano Paltera / For The Times