I have been working out off and on for a few years now, and have just started to become dedicated to working out for the past 2 months. I have a good routine (a push/pull plan) and work out 4 days a week for about an hour a day. I don't really pay to much attention to my legs however. I find when ever i do exersises like leg presses, my knees get really sore the next day. In fact, I think my knees in general are not very good because whenever I move in/out off school, I feel them getting really sore the next day from all the lifting. Is this common? Should I not do leg exersises, or should I do leg exersises to build up my knees so they won't get sore?