Hi I'm totally new to all this stuff and have a question. My knees have always bothered me to some degree, especially if I'm up and about all day, or doing a lot of getting up and down (I used to sell shoes and they would kill me after a day of that). The few times in the past when I have done some weight lifting, anything that involves my legs bending has ended up causing pain in my knees. Is there any excercises I can do to strengthen my legs that would avoid causing my knees to have to lift weight like that? I thought about using an elliptical machine or something like that, but my personalized workout says to avoid cardio since I want my calories for muscle mass. Any help would be greatly appreciated!