At The End On November Last Year (2016) I Was

at the end on November last year (2016) i was running cross country with my school and i felt something go out in my knee and then i collapsed on it and couldn't get back up or put any pressure on it was extremely painful, there was an ambulance at the cross counrty event and they told me that it was most likely dislocated so i went to the hospital and x rays were clear and i got told i torn ligaments and that it was dislocated i got put on medication (didn't realy help) and was in a brace , pain wasn't getting anyway better so i had an mri and the mri was clear (nothing was shown to be wrong) went back to the hospital and they said it look like it was never dislocated and that there was nothing wrong (but another doctor told me that it was) so they took the brace off and said i had to do Physio , the pain is just as bad now but apparently nothing is wrong , What could this be ?