hi I injured my back 4 years ago. I hit it very hard around the SI joint off the corner of a table. It was very painful. It took a little while to get better. I had a twinge in my back whenever I sat down. a few weeks later I resumed my fitness regime. I went to aerobics and I felt three pops in my lower back which I presume were discs popping, my back seized up for a few days but then I was left with a dull ache across my back and a tugging sensation in my left leg whenever I lift it.also some pain in the left hip. It continued to get better and I was left with a little pain. I had an mri which showed nothing. I recently found out that the place which conducted my mri actually scanned my upper back. I only found out that this year when I also developed really bad groin pain both sides which stopped me walking. I had my left hip done I consequently had the lumbar area done however they did not mri the sacrum or the part which I hit initally. I now have developed a similar problem on the other side. The groin pain gets worse when I walk up hill or if I tighten my stomach muscles. I would like to see a sprecialist. what kind of one should I see, should I check that no nerves were damaged by the inital impact.