The combination of stick use, a high-speed projectile, and vigorous physical contact makes ice hockey a sport in which injuries occur with regularity. Most of these occurrences are within the natural flow of the game and they are unavoidable; some common hockey injuries are a result of play that goes beyond the framework of the rules, yet are accepted as a risk of the sport.
For position players, being all players except the goaltender (goalie), the most common unintentional injuries are those sustained as a result of a body check or other contact either with an opponent or created by the opponent driving the player into the boards surrounding the ice surface. The boards, and the Plexiglas material that is built above them, are designed to absorb a considerable degree of the force created by contact. The average National Hockey League (NHL) hockey player is approximately 6 ft 1 in tall (1.85 m), weighing 210 lb (95 kg); each player wears another 30 lb (12 kg) of protective equipment. Collisions can occur when one player is stationary
The most serious injury caused by the types of body checks permitted by the rules is that of concussion. Players in every league in the world must wear helmets, but this protection is not complete given the forces created by body checks. Due to the cumulative nature of the damage caused by repeated blows to the head, and the ever-present risk of such contact, concussions are a particular concern to ice hockey players.
A particularly dangerous contact that occurs in open ice situations is knee-to-knee contact between offensive and defensive players. This event is the most common cause of the serious knee injuries that arise in ice hockey; most other knee injuries are more minor twisting-type mechanisms, often arising when the player catches a skate in the ice when attempting to change directions.
A number of different injuries occur due to accidental contacts between players, the sticks used, and the puck. Sticks have caused many serious injuries through the history of ice hockey; significant facial scarring and the loss of an eye are the most serious. When a defensive player attempts to block a shot directed at his/her team's goal, broken bones, particularly to the ankle and lower leg, are common, in spite of the protective equipment worn.
Goaltender is the most dangerous position on a hockey team; to face the pucks that are shot at speeds in excess of 100 mph (160 km/h) requires courage, as well as the physical skills of agility and hand-eye coordination necessary to prevent goals from being scored. The goaltender absorbs significant physical punishment, both from the pucks stopped as well as through collisions with opposing players in the vicinity of the goal crease. Unlike the position players in front of him/her, the goaltender must move quickly and acrobatically with his/her arms and legs; injuries to the hamstrings, groin muscles, and lower abdominal muscles of the goal-tender are common.
As with many team sports, it is the illegal and unsanctioned types of physical contact that often result in serious injuries to the participants. Hard slashes with the stick to an opposing players' forearms or gloved hand while they are carrying the puck on their stick have been a frequent cause of broken wrists and fingers. Cross checks, an illegal delivery of a two-handed blow with the hockey stick to an opponent, often from behind, can cause injury to the torso or back of the player. Fighting, both the consensual variety and that precipitated by one player, is a further cause of injury. The worst incident of this type in the recent history of the NHL occurred in March 2004, when Todd Bertuzzi of the Vancouver Canucks delivered a vicious blindsided blow to the head of his Colorado opponent Steve Moore, and ultimately causing the fracture of one of Moore's cervical vertebrae. A significant number of injuries to NHL players are caused by the illegal actions of an opponent, through the administration of such blows, or through the use of the stick to strike or spear an opponent.