Partially torn ACL or fully torn after kneecap dislocation??? Please advise!?

i was in a terrible car accident in 1989 and my knee actually went through the dash board. I remember waking up at the crash site, and in the ambulance and in the er and seeing that my knee cap was on the side of my knee. I was in a brace 5 months, had to learn to walk and run again. That happen when I was 14. I am now 32 and i still to this day have that pain. It is really previlant when the weather changes. Especially right before it gets really really cold or rains. I love sports and played in HS and college and I have always fought through the pain. My dr told me that he would do a knee replacment if I continued to injur it. I had just sign to college to play volleyball and was not chancing losing that scholarship. I never went back. I am sure that I will eventually have surgery.