The back of my knee began hurting about 9 months ago but was only a 1/10 pain. Over last 3 months it has gotten worse. I thought it was flexibility so tried working it out but that has had no results and pain has increased. I cannot put my leg straight on ground while sitting but can while laying down but certain angles hurt about 5/10. Can only describe it as deep in the back of the knee location. Walking from class to class on campus hurts but if walking far hurts less. Pain normally is about4