By Dr. Rallie McAllister

If you're a physically active baby boomer, you've probably come to realize that there's really no such thing as a completely risk-free form of exercise [1]. Minor aches and pains are to be expected, and no matter how careful you are, there's always a chance you might trip and fall on the treadmill or drop a dumbbell on your toe.

If you're worried about the toll that your exercise [1] program is taking on your knees, however, the results of a long-term study published in the February 2007 issue of Arthritis Care and Research may put your mind at ease. Researchers at Boston University reported that moderate exercise [1] doesn't increase the risk of developing arthritis [2] of the knee in older adults.

The study included more than 1,200 participants with an average age of 53. At the beginning of the study, the participants had knee X-rays performed and answered questions about their exercise [1] habits and symptoms of knee aches, pains, or stiffness.

The same individuals repeated the process approximately a decade later. After analyzing the participants' X-rays, exercise [1] patterns, and knee symptoms, researchers found no relationship between moderate physical activity -- including walking and jogging -- and the development of osteoarthritis of the knee.

Although osteoarthritis can strike virtually any joint in the body, the knee is the one most commonly affected. The risk of developing the condition increases with age: Approximately half of adults over the age of 65 have been diagnosed with osteoarthritis.

As a progressive, degenerative disease, osteoarthritis is caused by a breakdown of the cartilage within the joints [3]. While healthy cartilage is a firm, rubbery substance that serves as a cushion and shock absorber for joints [3], the cartilage in arthritic joints [3] is typically brittle and thin, and often becomes ragged or torn.

Next: Osteoarthritis > [4]