Risk is inherent in any activity you choose. I have seen alot of broken bones, blown out knees, etc. over the years...and have even experienced a few myself, but....it seems to me that there may be a certain lack of control when someone breaks a forearm blocking a kick in a sparring class. Most injuries tend to occur during regular classes when people are learning and practicing new techniqes, not during a sparring match where skill level is matched with skill level. Lower belt levels should not be sparring full contact, black belts should have the control to deal with a less skilled student. JMO