According to an emergency room study, over 30,000 people suffered hockey related injuries in the United States between 2001 and 2002. Over 18,000 children under the age of 18 suffered injuries according to this study. Hockey is a breeding ground for injury due to the type of surface (ice), equipment used (sticks and blades on skates), the velocity of plays, checks, and collisions, and finally the frequency of fist fights. It is important for coaches, referees, and league officials to keep control of the games and practices to limit the amount of injuries that take place. You can read more about the study at Characteristics of Ice Hockey Injuries in U.S. Emergency Rooms.