6 total. 4 in class, 2 in tournaments, and quite a few near misses where muscles were pulled. This isn't including choke outs which is quite a bit higher.
Actually both tournament breaks was from spazzing. I had the lock, and my opponents tried to get out of it, dislocating their own joints in the process. In class it tended to happen while rolling. When I was less experienced, I wouldn't release an arm bar or shoulder lock until I felt or heard a tap. A few guys were trying to tough it out and not submit, and they got hurt in the process. It's personally ever happened to me because I'm smart enough to tap when I know someone has a lock and is applying pressure. There's no reason to try to fight through a perfect lock, especially if we're just practicing in class.
Of course now that I'm more experienced, if I feel that someone isn't going to tap I release and simply transition to something else.
Both occurred years ago when I was a white belt competing in local Bjj tournaments. I don't know how the rules in your sporting events work, but a ref isn't going to stop a match because they "think" someone has a lock on someone if the other guy is still fighting through the lock. Could you imagine the carp storm if a guy lost because the ref "thought" he was caught in an unescapable arm bar or leg lock?
BTW, Thanks for giving me yet another reason to not compete in Judo tournaments.
Check out the web, there's plenty of vids of people getting their limbs broken at Bjj/Grappling tournaments. No one does it on purpose, it's simply the nature of the sport.