I have had a few bouts with it. The Chiropractor I went to referred to the situation as a "subluxation of the sacro-illiac". A few treatments (adjustments) and I was good to go. Except for the time I was transferring a gas extractor from one shale shaker to another and slipped and landed on the flow line. That took three months to get back into shape, mainly because I continued working for a week after the injury. I couldn't sit, but I could stand or lie down, so I worked standing or lying down for that week. Finally, after I stood on a 4-inch pipe and reached overhead to splice some cables, I had to go to the house. No fun, and anyone who has Lumbar involvement has my sympathies. That pain was up there with serious dental pain, as far as I am concerned.