American football has long encouraged a tough, take-no-prisoners attitude as a central ethic of the sport. While there are significant rules in place to govern the protection of the participants and the general safety of the game, these regulations deal with the minimization, not the prevention, of serious potential harm.
The typical team in the National Football League (NFL) will experience an injury for almost every player on its roster in the course of a year, some of the season-ending variety. The size of the athletes at every position in the NFL has increased substantially in recent years. As an example, in 1980 there were only 20 men who weighed in excess of 300 lb (135 kg) in the then 28-team league; as of 2006, the average NFL offensive lineman exceeds that weight. It is a simple proposition of physics that the faster and heavier the players are who come into collision, the greater the likelihood of an injury. When lower percentage body fat of the modern player and greater muscular power and refined tackling techniques are added to the equation, American football becomes a potentially dangerous sport.
Greater athletic size has translated into a correspondingly greater number of non-contact injuries sustained by these athletes. The most common of these injuries include:
- Hamstring strains and tears are caused by explosive running movements.
- Groin pulls and tears are usually caused by quick lateral movements or stretches that overburden the groin. The serious injury sometimes referred to as a "sports hernia" is in fact a tear of inguinal ligament in the groin.
- Ankle sprain is an injury more common in football than in other sports, representing the damage caused by a twisting motion in the upper aspect of the lower leg, and pressure from the ankle bone (talus) applied between the bones of the lower leg, the tibia and fibula.
- Achilles tendonitis and ruptures happen frequently.
- Heat-related injuries occur especially in preseason training camps held in the summer months, or in games that are played indoors. Heat cramps, resulting from dehydration and low mineral levels are common, particularly among the larger athletes.
- Repetitive strain injuries to the shoulder structure and the ulnar collateral ligament of the throwing elbow are sometimes sustained by the quarterback.
The possible range of injuries caused by contact in football is almost as infinite as the ranges of motion through which the body may move during competition. It is an irony of the game that the protective equipment is a key instrument in injury causation. The helmet is the primary example of such a device. When contrasted with rugby, the protective equipment-free sport from which American football is chiefly derived, the difference in the injury rate is startling, even when the different physics of the permitted tackling and types of contact are taken into account.
The head and the neck of the football player are prime injury areas. A greater emphasis on proper tackling technique in recent years has reduced the incidence of serious neck injuries to an intended tackler; when the tackler leads with the helmeted head, there is a significant risk of serious concussion, neck fracture, and cervical spine and spinal cord injury. Helmet-to-helmet contact, especially when both players are moving together at full speed, is a frequent cause of concussion.
The large size of the linemen blocking one another and the development of blocking techniques whereby the blockers seek to jam their hands on the shoulders of the oncoming opponent places significant strain on the entire shoulder and elbow mechanism, leading to potential dislocations of either joint, and repetitive strain injuries.
The fingers of the hands of every football player are exposed to dislocation from the manner in which the ball may strike the hands, or if they are otherwise stepped on or twisted. Most players now wear protective gloves to provide additional support for the delicate joints of the fingers.
Knee injuries are the leading cause of disability among football players. Some serious tears of the anterior cruciate ligament (ACL) do occur in non-contact situations, when players have their feet get caught in the playing surface; the majority of football ACL injuries occur when the player is moving in a particular direction, and is struck on the knee causing the joint to move in an opposite and forceful way. The large men who play the line positions may be injured in this fashion when a player behind them is rolled onto the back of their legs while they are upright and endeavoring to block another player; their extreme weight accelerates the movement of the knee, causing the injury. For this reason, many linemen wear knee braces even if they have never sustained an ACL injury.