i wanted to start some leg workouts to build some mass on my stick legs, but my knees have been really bothering me. i started squats last week and noticed when i lift the weights back up, my knees lock up and makes cracking noises. there's also a sharp pain. anyone know some alternative workouts or maybe a way to get stronger knees so i won't run into this problem? btw, i'm not a body builder or anything. i am 25 yrs old, and just started working out. i just got a membership to a gym and i've been working to get some lean muscle on my upper body but my legs need some SERIOUS work. any input will be appreciated.