(Describer) Streams of light collide to create a globe filled with water. Title: Science Nation. A man walks on a sidewalk.

[explosion]

(male narrator) Aches and pains got you down?

(Describer) Lloyd Hanson:

Suddenly, I developed pain in my knee and it just progressively got worse. I didn't want to walk anymore.

(narrator) The way you walk could be wearing out parts of your body.

(Describer) Suzanne Dancer:

I've had knee pain off and on for a couple years.

(Describer) Mark Cutkosky:

Roughly 50% of people, as they age, start to show some evidence of osteoarthritis of the knee.

(narrator) What if you could alleviate pain by changing your stride? With support from the National Science Foundation, mechanical engineer Mark Cutkosky and his team at Stanford University want to help people live healthier lives.

(Cutkosky) Let's get started.

(narrator) They're outfitting test subjects with sensors and then have them hit the treadmill. When Lloyd takes a step, custom software precisely calculates the forces on his joints. And that data helps determine if a gait change might alleviate pain.

(Cutkosky) We use a biomechanics model and say, "Aha! "If you turn your toes, or your knees out, you could reduce adverse loads on the knee joint."

(narrator) One major cause of knee pain is uneven wear and tear on the cartilage, which leads to arthritis.

(Describer) Cutkosky and a colleague review a knee x-ray.

You're comparing this gap to that gap.

(narrator) The idea is to shift weight from the worn-out area to a cushioned area of the knee. Instead of Suzanne walking with one foot pointed out--

(Suzanne) They suggested that I turn it in, which feels strange.

(Describer) A woman behind her points a camera at Suzanne on a treadmill.

Straighten out your right foot and point it straight ahead.

(narrator) They recommend a similar fix for Lloyd.

(Lloyd) The pain is almost nonexistent. It's amazing. It's--It's truly amazing.

(narrator) To help test subjects learn their new gaits, the team developed a biofeedback device, and they're working on a portable version to reinforce the modified gait outside the lab.

(Describer) Pete Shull:

Instead of a lab computer, you use your cell phone.

(narrator) Stride therapy isn't just for people in pain. Athletes could improve their moves with this biofeedback technique. For Science Nation, I'm Miles O'Brien.

(Describer) A man dunks a basketball. Funding to purchase and make this educational program accessible was provided by the U.S. Department of Education. Contact the Department of Education by telephone at 1-800-USA-LEARN, or online at www.ed.gov.