I'm Just Sayin'

Saturday I had a great walk along the river front, and made one circuit around Mast Park. One of the people running in the park was a young lady of around 30-35. She had the slim build of an avid runner. I noticed that she was wearing a brace on both knees. That got me thinking-if you need a brace on both knees, could that be your body telling you that maybe it's time to take up another activity besides running (on a concrete sidewalk no less)?