What Causes Knee Pain?

I have had three hip arthroscopic surgeries for labral tears,bone reconstruction of the ball and socket, and releasing my IT band. I am 20 years old and am now in pain again but now my knee is killing me too. I had xrays and an MRI that were both clear showing no injuries of the knee...Could it be my hip again? or could it still be my knee....i am so frustrated my leg is falling apart and the surgeon probably wont touch my hip again since its already been operated on three times...any ideas?