SAN FRANCISCO — Players in the National Football League (NFL) have long complained that they sustain more injuries on artificial turf than on natural grass, and now an independent study reported here backs them up.
Analysis of all injuries listed in an NFL database from 2016 to 2021 showed that every type of common injury was more common on artificial versus natural grass, noted Ryan Whalen, BS, of the Steadman Philippon Research Institute in Vail, Colorado.
But not all forms of artificial turf are created equal, it appears, at least for their contribution to player injuries. So-called slit-film turf, which has a softer feel and is designed to break down with use, was associated with higher injury rates than either stiffer monofilament products or natural grass, according to a poster presented at the American Academy of Orthopaedic Surgeons annual meeting.
Until the 1960s, all football was played on natural grass. In professional sports, that changed with the debut of Houston’s Astrodome, the first fully enclosed major league baseball stadium, where the game was played on (naturally) AstroTurf. The 1960s also featured the replacement of many cities’ baseball and football stadiums built in the first half of the 20th century with cavernous multipurpose structures. Artificial turf’s easier upkeep made it a popular choice for these facilities.
But practically from the start, players complained that these surfaces were much harder than natural dirt and grass, and more importantly, tended to grip their shoes more strongly, causing their feet to “get stuck” and strain or tear cartilage, ligaments, and tendons. Teams, however, downplayed these concerns, suggesting that the rising injury rates were simply fallout from players becoming bigger, stronger, and faster (which indeed they were). And in truth, it’s impossible to say that any particular player’s ligament tear incurred on artificial turf would not have happened on natural grass.
The new study makes it more difficult to argue against a contribution from the surface itself.
During 2016-2021, a total of nearly 1,700 games were played, divided almost equally between artificial and natural surfaces; about three-quarters of the artificial surfaces were slit-film. The overall injury rate per game in this period was 1.92.
Whalen’s group found that each of the following types of injury — ankle, hamstring, groin, calf, quadriceps, anterior cruciate ligament (ACL), medial cruciate ligament (MCL), leg/ankle/foot fractures, and Achilles tendon — were more frequent on artificial surfaces (both slit-film and monofilament) than on natural grass, by 2% to as much as 62%.
For example, rates of ankle injuries were 0.561 per game on artificial turf versus 0.498 on natural grass. The 62% higher rate was seen for MCL injuries, for which per-game rates were 0.089 on artificial surfaces versus 0.055 on grass.
But for many (but not all) of these injury types, rates were similar for natural grass and monofilament plastic surfaces. Whalen and colleagues also compared injury rates for slit-film surfaces to the combination of natural grass and non-slit artificials. Most showed higher rates for slit-film surfaces: by 30% for ankle injuries, 33% for hamstring pulls, 45% for quadriceps injuries, and 38% for Achilles tendon strains and tears.
On the other hand, ACL tears, groin pulls, and lower extremity fractures were less frequent on slit-film turf versus grass and monofilament. Ankle injuries on slit-film appeared to be a special concern: the data showed a rate of 0.671 per game on this surface, versus 0.515 on other types.
“This work can help the NFL and the NFLPA [players’ association] put forth guidelines for playing surfaces in the NFL to limit the number of injuries players are at risk for,” the researchers concluded.