I leaned on my knees to close a window and I heard something snap. I had teriible pain for about 15 minutes and then the pain went away. 2 weeks later as I was sitting I could feel a twist in some area near my knee and I could not put any pressure on the leg for about 2 hours. It was excruciating pain. after 3 hours I was able to walk and there wasn't any pain at all. I went to the doctor, had an ex-ray and I was told get an MRI. What could it be?