The NFL is known as an aggressive and brutal sport, with injuries happening every game as a result. Unfortunately, some injuries have forced players to end their careers. Here is a list of career-ending injuries. Running back Terrell Davis won two Super Bowls and a Super Bowl MVP with the Denver Broncos in his first four seasons in the league However, Davis would tear his ACL and MCL in 1999 and was unable to return to his previous form before retiring after the 2001 season. San Francisco 49ers quarterback Steve Young notched seven Pro Bowl and three All-Pro nods, as well as a Super Bowl win in his first seven campaigns as a starter. However, the repeated hits in games, as well as a concussion, forced Young to retire in 2000. Bo Jackson is considered one of the greatest athletes ever due to his exploits in the MLB and the NFL, where he became the first athlete to be named an All-Star in two major sports. However, Jackson suffered a severe dislocated hip in an NFL playoff game in 1991, which forced him to retire from football before he quit baseball just a few years later. In a game against the Denver Broncos in 2007, former Buffalo Bills player Kevin Everett attempted to make a tackle but would immediately dislocate and fracture his spine, forcing him to retire. After being named to the Pro Bowl as a rookie in 2009, wide receiver Johnny Knox looked destined to become an important player for the Chicago Bears. However, during a 2011 game against the Seattle Seahawks, Knox collided with Anthony Hargrove and underwent immediate surgery in order to avoid paralysis. He later retired from the NFL.
