HELP!?!??! HORRIBLE KNEE PAIN!?!!?

I am a 13 year old girl. I have had two arthroscopy knee surgeries in the last 10 months and now my knee is hurting servearly. I was told that I shouldn't have knee pain? When ever I try to sit criss cross apple sauce, (legs are crossed) I get horrible,sharp,pulling,type pains in the inner part of my knees...I had a slight case of knock knees, if that could help with your explanation...Could the pain be from the medial mensicus causing me problems and should I get it checked out? Please help!!