All I've ever had is a broken nose from doing 'light sparring' with a lower kyu grade. Only because the control wasn't there and there was no face contact allowed... Crap happens though. You don't have to be in a class for bumps and breaks. Other than the usual bumps, I've had a hip year from repetitive movements but again, I've got weak hips since childhood. A lot of older instructors get joint issues but training has moved away from The old brutal stuff, probably because people now understand the negative effects it has on the body. Safe to say, karate is safe if you're in a good, controlled environment.