The first time I sat on a square foot stool and somehow sat right on the corner where two boards came together and there was little to no padding. It got pushed in and over to one side and caused the muscles in my lower back to spasm really bad. I had to have injections in the area to reduce swelling and after a few days I was bending over and it popped back into place violently. After that, it didn't take a whole lot for it to happen again. The second time I was laying on the floor on my stomach and my wife came and sat down on my behind just being silly. Well, this time was worse than the first time. I couldn't move, couldn't roll over, nothing. I had to sleep on the floor that night. Started with the ibuprofen and ice packs and the next afternoon it popped back into place but I was so sore I could hardly move for about a week. Several times after that it has happened but not as severe as the first couple. I've gone to Physical Therapy and they have shown me exercises to do while laying on my back with my knees up and feet on the floor that use your muscles to pull it back into position. When I feel pressure and pain in my tailbone I can do these and it relieves it before it gets full blown out of kilter. But it pretty much hurts all the time. I can't get comfortable for very long so I have to keep moving and shifting positions whether I'm sitting, standing, or laying.