Just tripping a bit messed up my SI joint pretty bad a few years back. It didn't even seem serious at the time, just a bit of a stumble off of the curb, but the next day I could barely get out of bed and was in pretty serious pain for several days. Couldn't go up stairs and had a tough time getting my pants on. Still acts up sometimes.
This can definitely happen, I had a like crooked hip for a few days after I bumped into a table while lifting something. I dont think this could ever result in something good though like chiropractors claim.
