they say that running up and down the stairs, and jogging will wear and tear your knees, I didn't believe but now i do. My knees are starting to ache after jogging and running up & dwn the stairs at least twice a week. This sucks coz my colleague's knees ached and now she cannot jog as it is excruciatingly painful. Maybe I should land more gently each time my feet touch the ground so as to lessen the impact on my knees but i would definitely look comical trying to run like that. Sigh...