SATURDAY, Aug. 7 (HealthDay News) -- Protecting your knees when you're younger may help prevent serious problems such as arthritis and the need for knee replacement when you're older, an expert advises.

Research indicates that nearly half of adults develop arthritis in at least one knee by age 85, and the risk is even greater for obese people. Extra pounds increase the strain on knee joints, noted Dr. William J. Bryan, an orthopedic surgeon at the Methodist Center for Sports Medicine in Houston.

"Every time you take a step you apply three times your body weight to the knee. When you run it's five times, when you jump it's seven times. If you are experiencing frequent knee pain, lifestyle changes might be in order," Bryan said in a news release from the Methodist Center for Sports Medicine.

Weight loss is 70 percent diet and 30 percent exercise, he explained. "If you think you can eat the same and exercise the pounds away, you are mistaken. You have to change your attitude about the refrigerator for weight loss to happen," he said.

In terms of exercise, low-impact activities such as swimming and cycling are better for your knees than high-impact workouts such as running or aerobics. Having good core strength (abs, back and pelvis) also helps protect your knees, Bryan noted.

"If you have a strong core, you can better position your foot or knee on the ground to prevent damage. This is true whether you are exercising or performing mundane tasks such as getting out of the car and walking down the stairs," Bryan said in the news release.

Orthotics may also help protect your knees. Your knees can be subjected to abnormal stress if your shoes don't give you a stable base as you walk. Many patients experience dramatic reductions in knee pain after getting orthotics or shoes specifically made to fit their feet, according to Bryan.

"If you have knee pain that has lasted more than two weeks, you need to see a doctor because there might be something mechanically wrong with the knee," he said. "Making a few lifestyle changes might give you a better chance at staving off arthritis and/or eventual knee replacement," he added.

More information

The U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases has more about knee problems.