I knew a chap when I was a kid who had to have this surgery performed on one
leg due to an illness that caused
leg-length discrepancy. It worked
well and his legs are almost the same length now, but he was in agony for a good couple of years, and he can't do any real exercise now - and of course, his stretched leg is very skinny and a mass of scar tissue.
As you might guess, I know all this because I've considered the surgery myself.