American football has its roots in rugby and similar, somewhat “free-for-all,” European games based on moving a ball from one place to another through various means, some dating back as far as the 1100s. Immigrant settlers introduced various versions of the same concept. In the 1800s, students in Princeton and Harvard began playing similar ball games that were rather violent and unruly, but eventually evolved to the “Boston game”, which had rules for running and kicking the ball and reflected soccer rules. Walter Camp is acknowledged as the father of American football. He put forth proposals from 1873 and 1880 in various gatherings to establish a framework for American football. 

Among other things, Camp introduced the line of scrimmage, snap rules, and the principle of five yard advancement within three downs. He influenced the development of the game for the enjoyment of participants and spectators alike. Today, American football is a sport slowly gaining popularity worldwide. In the United States where it is the most popular sport, it is played by athletes at the youth, high school, collegiate, and professional levels. Rules of the sport are dependent upon the level at which the sport is being played.

American football injuries are myriad, owing to the high-velocity, collision nature of the sport. The lower extremities are most injured, usually the knee, for example, anterior collateral ligament (ACL) or medial collateral ligament (MCL) sprains or tears, or meniscal injuries. Most injuries are sprains or strains, such as ankle sprains. Football players also get a lot of contusions, fractures, concussions, and dislocations. Football neck injuries can be catastrophic, but have declined dramatically through the years due to improvements in coaching, equipment, and fitness. Rule changes in terms of tackling and blocking have also helped contribute to this decline.