A recent study found that NFL games played on turf showed significantly higher rates of lower-leg injuries.
Across sports and competition levels, playing surfaces have been switching from natural grass to artificial turf. This has several health ramifications. Some researchers have speculated that the rubber polymers used in artificial turf cause cancer. Although turf's carcinogenic properties have not been proven, a recent study of NFL players showed that the incidence of knee and ankle injuries is significantly higher in games played on turf.
The first NFL stadium to use an artificial playing surface was the Houston Astrodome in 1966. The surface, called AstroTurf, was manufactured by Monsanto and consisted of a padded-carpet over asphalt. In the 1990's infill surfaces became popular and are widespread today. Infill surfaces consist of an interwoven mat of polyethylene fibers filled with rubber particles. The frequency of NFL games played on turf has been increasing over the years as more NFL stadiums adopt turf. The figure below demonstrates this trend over the previous decade.
Several studies have looked at injury rates in football players based on field surface. A study done in the early 2000s found that ACL injury rates of high school players are higher in games played on turf. However, the same study found college players were more likely to sustain an injury on grass than turf. A recent study looked at several different lower leg injuries in NFL players using extensive data collected by the injury surveillance system maintained by NFL trainers (An Analysis of Specific Lower Extremity Injury Rates on Grass and FieldTurf Playing Surfaces in National Football League Games : 2000-2009 Seasons; 2012. Elliot B. Hershman, et al.). The study used data from NFL seasons from 2000 to 2009.
The aforementioned study looked at several different lower leg injuries in NFL players: knee sprains, MCL and ACL injuries, ankle sprains, inversions and eversions. Although all injury categories demonstrated a higher frequency in turf than grass, MCL (median collateral ligament) injuries and inversions (an ankle sprain where the ankle is twisted inwards) both did not show significance. The injuries that did show significantly higher prevalence on turf were knee sprains, ACL injuries, ankle sprains and eversions. The figure below shows the injury rates in NFL players based on a density ratio of turf over grass injury rates.
ACL sprains occurred at a rate 67% higher on turf than grass. Eversion ankle sprains occurred at a rate 31% higher on turf than grass. Despite the significantly higher rates of injury on turf, this study was limited because it did not suggest any mechanisms by which turf causes higher lower-leg injury rates nor a means to make artificial surfaces safer.