I'm an 18 yr old female and have had hip and knee pain for over 2 years. my knee locks up and i have to rotate it to make it pop. what could this be?

Hard to say: There is a condition known as tensor facia lat a syndrome that causes hip and knee pain and sometimes causes the knee or hip to pop. It is caused by a tightness of the tensor fascia lat a which runs down the side of the thigh and inserts just lateral to the knee. A meniscal tear in the knee can cause popping as well. Thank you for your question.

Meniscus.: It could be a meniscus tear or a loose body floating in the knee. See an orthopedic surgeon for evaluation.