If you've been listening along, you know that there's one category that we haven't been talking about yet. And that is chronic back pain with leg pain. And that typically instead of being just in one leg, is usually in both, although not always, most often that's a function of bony overgrowth and that's called stenosis. And the demographic for that is people who were sometimes in their forties but most often you'll see it in late fifties, sixties, seventies, eighties and you'll actually see it in 90s. And what happens is, is the bone just gets thick and the center of the bone and the vertebrates, which is where the nerves run and higher up the spinal cord, that that just gets tight. People start having a very stereotyped presentation. And that is, Ooh, Gee, my back starts hurting when I'm walking or standing. And if I'm going through Walmart or Costco that I have to use a grocery cart. Or, Gee, I need to park really close to the front of the store because when I'm trying to get into the front of the store, I got to have the shortest distance possible. Or, Gee, I'm standing in the checkout line and you know what? My legs are starting to hurt. My back is starting to hurt and I got to find a place to sit down now. Not everybody actually hurts with spinal stenosis and I've seen a number of patients and it's been described where patients actually will have troubles, but it's not that it's painful, it's that their legs get woody. They sometimes feel like their legs are numb, the legs won't want to do what they want them to, and those symptoms will start in the back and extend down the legs. Although some patients will tell you, it seems like it starts in the legs and actually goes up into the back. There was a recent article published a couple of years ago. We used to think that stenosis in particular didn't cause nighttime pain, but if I remember right off the top of my head, about 56% of patients in that study that they looked at who had stenosis also had trouble sleeping at night because they had leg pain. And so that tells you that sometimes we can learn something over time and looking backward at patients and be a little smarter about symptoms. So those are the four major groups, and there are four major presentations.