Sounds like everybody gets there eventually. For reading as much as I did before getting a bike you'd think I would've run across that. Maybe I did and my 1980s mentality blocked out anything that looked like safely gear.
Like 30 seconds after I did it there was a half ping pong ball size welt on my knee. Was a little hard to walk for a few, but I figured I'd hop back on. Shortly thereafter the SECOND one in that spot made me lay down and contemplate life and the choices I made for a minute.