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Exercise helps to build knee cartilage: Seven's On Call

Good news for people worried that exercise will lead to painful knees.

WABC—September 28, 2007

Exercise is great for the heart, but are you wearing out your knees in the process? A recent study in the journal Arthritis and Rheumatism says that if you do it right, exercise builds up the cartilage in the knee and makes it stronger.

Michael Will is using physical therapy to strengthen his right knee after surgery to repair cartilage that was damaged in an accident five years ago. Before that, he was an athlete.

"I played tennis division," said Michael Will. "I played tennis all my life since I was 11 years old."

Maybe it was his healthy knee cartilage that prevented a worse knee injury. That's what this new report says; that the more you exercise, the stronger and healthier your knee cartilage becomes.

"Cartilage is a cushion," said Riley Williams, M.D. at Hospital for Special Surgery. "Having more of it will allow you to do more with it throughout your lifetime."

Here on this knee model is the cartilage in blue on the end of the thighbone. You can see it on an MRI - the leg bones above and below. The thin grey layer of cartilage acts like human Teflon to cushion knee movement.

The study did MRIs on healthy men from 50 to 80 years of age. It found the more they exercised, the thicker the knee cartilage became.

You don't have to do much exercise to strengthen the cartilage, just about 20 minutes, once a week of exercise that increases the heart rate and makes you sweat.

It's not known whether thicker cartilage will protect against arthritis, but perhaps more of a good thing is better.

The type of exercise? Low impact work on the elliptical machine is good. Running is okay as long as you don't overdo it and stop if it's painful. And walking may be all you need.

"All patients, whether doing low energy exercise like walking or doing a little more high energy exercise, had a beneficial effect from that exercise over the 10 year period," said Dr. Williams.

Dr. Williams says if you're in the 50s, 60s and 70s age group, as were the people in this study, and not running now, starting exercise with that high impact, high energy may be hard on your knees. It's best to begin with walking.


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