Easy strengthening exercisses for knees

This is from WebMD. I went through all the clear descriptive slides with pictures and they look like great exercises that you can do at home or at the office. I'm going to do them daily - thought it might be helpful for some folks:

http://www.webmd.com/osteoarthritis/joint-injections-13/slideshow-knee-exercises?ecd=wnl_art_100413&ctr=wnl-art-100413_promo_1&mb=XENxDayi8IkS16MH2JQtk%40HnVev1imbCPWNsqsL9r%2fA%3d

Frances