The myth of the fabled runner's knee has haunted pavement pounders of all ages. However, a recent article in The New York Times has sought to defeat the specter of worn-out, arthritic knees on avid joggers. Apparently, not only will running not wear out your knees, it could even help protect them against arthritis.

A 2008 Stanford University study followed 500 longtime distance runners over 50 for nearly 20 years. At the study's onset, the runners ran approximately four hours per week, which declined to an average of 76 minutes per week after 21 years. Additionally, 6.7 percent of runners had mildly arthritic knees compared to none in an age-matched control group, reported The New York Times. Now, the old school of thought would lead you to believe that after 20 years, runners experienced a higher incidence of arthritic knees. In reality, the reverse happened. Only 20 percent of runners experienced arthritic knees compared to 32 percent in the control group.

http://www.thatsfit.com/2009/08/25/the-myth-of-runners-knee/