I Hyperextended My Knee Doing Hurdles A Year Ago But

I hyperextended my knee doing hurdles a year ago but when I went to my Dr he had an xray and mri done and besides a little fluid build up there was nothing wrong, but I am still constantly in pain. I can't stand for more than a couple hours without excruciating pain and it gives way too often. my Dr said he won't refer me to an orthopedic because there was no proof that something was wrong. Why am I still in pain then? It hurts on the inside of my knee and in the back. I just want to find the reason for my pain. Because of the giving way I have twisted my ankle as well. Thank you for taking the time to review my question.