Around 1982 I was knocked off of my motorcycle and bounced on my lower back @45mph. It prutrudes visibly but doesn't bother me too much most of the time. If I don't do any climbing for a while then climb, it comes alive. The last 3 weeks I've been sick again so very little saddle time until Saturday, when I did some steep climbing. FML, it was like someone was sticking a knife in my spine until I got home and got on the floor for a half hour.
Oh yeah, in 2007 I fell off a 40 foot cliff while mtb'ing and did compression fractures to 2 vertebrae around shoulder blade level. Those babies keep me awake sometimes until I can find a way to lie without pissing them off, or one of my shoulders.