Do I have a torn meniscus?

I have had knee pain for several years now but every time I go to the doctor they say it's patellofemoral pain syndrome and that I should just rest it. I've tried that many times and it hasn't worked. Now ever since December 2012 it's been a lot worse. I could barely walk and stairs were almost impossible. It's gotten better but I can't climb stairs or squat well. It also hurts when I run or when I put pressure above my knee while I'm sitting. I would greatly appreciate some insight. Thanks!