I'm a walking train wreck, but I've had two really bad ones.
I herniated a disk in my back when I was 20 in a sledding accident and had nerve damage down the right side of my body for over a year and a half after the fact. I could stand and walk (barely), or I could lay down, but if I sat down it felt like someone stuck an ice pick into my hip. Luckily I managed to fix it by walking as much as I was physically able, dropping 80lbs of fat and working my lower back muscles. Hasn't really bothered me in years.
The other one was when I worked at a circuit board components factory when I was 22. The factory was extremely old and the roof had collapsed ages ago and was rebuilt when the new owners bought the place. In that time, lots of rain and snow got in and the cement floor of the factory was more or less covered in pot holes. So, I was working as a temp working at the time, carrying a stack of boards and I stepped right on the edge of one of these pot holes and rolled my ankle horribly. I was actually momentarily standing on my leg bones and managed to hop and fall onto a pile of cardboard. Being as I was a temp worker, I had no coverage for injury or anything like that, and really needed the money, so I tied my boot up as tight as I could get it and kept working. My ankle hurts to this day, and actually ended up almost fusing at a 45 degree angle away from my body, so I have a slight limp and my ankle barely moves, especially when I've been standing all day. On the plus side, because of the way it fused, you can't get a heel hook on that foot, so when I go for leglocks, I always cross it over the top of the opponents leg and they go for it every time.