Does NFL Turf Actually Cause More Injuries? I Looked at 84,000 Player-Games to Find Out.

Online I hear a common argument: artificial turf is dangerous, players hate it, and the league should replace it with grass. The NFLPA has pushed this narrative for years and players always seem to talk about it after every high-profile injury. It is one of those arguments that just feels obviously true.

I wanted to know if the data supports this argument. So I pulled 16 seasons of NFL injury reports (from 2009 to 2024), covering 84,667 player-game observations across all 32 teams. The injury report is the weekly document teams are required to file before each game. The report lists every player dealing with an injury and their status: Questionable, Doubtful, or Out. I used Out designations as my injury indicator since those represent players who definitively did not play due to injury. That gave me just under 15,000 injured player-game observations to work with.

The First Result

I was very surprised by my first finding. Overall injury rate on artificial turf was 17.84% while on natural grass it was 17.82%. I ran a chi-squared test and it returned a p-value of 0.92, which means the difference is indistinguishable from random noise. This confused me since I expected the gap between the two to be larger and for this to at least somewhat lean towards the argument that turf surfaces are more dangerous to play on.

I decided to check injury type next, thinking that maybe the aggregate masked a real signal in specific body parts. My thinking was that artificial turf has less give than grass, which puts more rotational stress on joints when a player's cleats catch rather than release. Specifically I wanted to look at knee and ankle injuries since those are the major joints in the lower body that would absorb this stress.

When I split out the injuries I found that lower body injuries account for about 69% of all injuries on both turf and grass. Concussions were about 10-11% and upper body hovered around 20% on both. I ran another chi-square test across the different injury categories and got a p-value of 0.97, meaning that splitting out by injury mix still showed an indistinguishable difference across all the injury groups.

Finally I specifically looked at knee and ankle injuries across different surface types and got a p-value of 0.52 for knee (no difference) and a p-value of 0.12 for ankle, which was a weak directional signal but still was not statistically significant.

So at this point, the data was pretty clearly saying that artificial turf does not cause more injuries than natural grass.

The Next Finding

So since that first finding fell flat in supporting this argument I wanted to dig deeper. This is where it gets a bit more interesting. Initially I lumped all artificial turf as one category, when in reality it is not all the same product. The product has evolved dramatically since the 1970s and there are multiple suppliers that make turf in different ways.

I pulled in the raw surface type from my database which has records with the specific product installed in each stadium (grass, fieldturf, sportturf, etc). Using those turf types split out, I then ran a global chi-square test across all surface sub-types to see if there was anything worth investigating. That test came back with a p-value of 0.0089, which meant a signal existed. It just was not in the aggregate turf category I created early on.

Since there was a signal I wanted to dig a little deeper into this stratification. I ran a logistic regression with natural grass as the reference category to find where the signal lives.

AstroTurf: 17% higher overall injury odds versus grass. Modern FieldTurf: statistically indistinguishable from grass.

After doing some light research I found that modern FieldTurf is the dominant artificial surface in today's league, and it looks like it is not more dangerous than grass. The elevated injury risk that gave artificial turf its bad reputation actually traces back to old-generation AstroTurf.

One other surface worth noting is SportTurf, which came back with an odds ratio of 1.082 and p-value of 0.048, sitting right at the edge of statistical significance. I would treat this cautiously — the sample is about 4,500 player-games, which is large enough to detect small effects but not large enough to be confident they are real. It is a signal worth watching but not one I would draw a firm conclusion from.

Here Is the Part I Cannot Fully Explain

So since we figured out that AstroTurf was the issue when looking at overall injuries, I thought that looking at lower body injuries would make the gap between this surface and grass even larger. I was still thinking the biomechanical argument of extra stress on the lower body joints was correct.

I was shocked to see that for upper body and concussion the injuries on AstroTurf were statistically identical to grass, while lower body injuries were actually slightly lower (68.3% vs 69.5%). A chi-square test on the injury type breakdown returned p=0.85 — no meaningful difference.

The conclusion I can make is that AstroTurf produces more injuries overall, but that is it. The extra injuries are not concentrated in a specific category, or the AstroTurf sample (about 400 injured players) is too small to detect a category-level difference.

Severity Tells the Same Story

I started to think about what I could be missing so I turned to a new theory. I was currently comparing all injuries and treating them equally. A player who misses one game with a sprained ankle counts the same as a player who misses eight weeks with a torn ligament. If turf causes more severe injuries even at the same rate, the initial narrative could still be correct.

I built a severity score based on consecutive games missed per injury event. It uses a log curve that runs from 1.22 for one game missed to 1.90 for a full season. I ran a Mann-Whitney U test comparing severity distributions between artificial and natural surfaces and it returned a p-value of 0.41. No difference. The median injury on both surfaces is a single game.

Data Limitations

The weekly injury report records body part only, not diagnosis. "Knee" covers everything from a bruise to a torn ACL. A real difference in ACL rates between surfaces could exist and this dataset would not show it, because both would just appear as "Knee." Diagnosis-level data would require either medical records or a separate scraping project to pull historical ACL reports from news sources, neither of which I have here but I would love to add in the future.

Concussion underreporting is also a known problem. Research estimates public injury data understates concussions by 20 to 50% compared to electronic health records. Any concussion findings from this dataset should be treated with extra skepticism.

Another issue is that this data does not specifically tell us if the surface caused the injury. The weekly report is a status update filed before the upcoming game, so an injury that happened in practice or off the field that week still gets attached to whatever surface the next game is played on. I would need internal NFL data that tracks practice versus game injuries to address this properly, but that data is not public.

The Honest Summary

The data does not support the broad claim that artificial turf causes more injuries than natural grass. What it does support is the narrower claim that old-generation AstroTurf is more dangerous than grass. Those are different claims, and the public conversation tends to conflate them.

The league has been steadily replacing older surfaces with modern FieldTurf and grass for years. The risk profile of artificial surfaces has improved not because the product got safer but because the dangerous product got phased out. The narrative has not kept up with the product evolution.

Whether modern turf causes worse injuries at the diagnosis level, even if rates look the same, is a question this dataset is not equipped to answer. That would be the right next study.

Finally, I am missing a lot of factors that could go into injuries beyond what I stated in the data limitations above. Weather, previously existing injuries, age, and even position can all come into play when determining if a player will get injured. That said, I want to make sure you do not walk away with the wrong takeaway. Right now I do not have enough data to support the claim that turf is a driving cause of injury, and more specifically injuries like ACL and MCL tears. However, on the other side of the coin, we may also be overreacting to how dangerous modern turf surfaces actually are.

What Comes Next

I also wonder if players tend to play more carefully on turf than on grass. This would essentially be like the seatbelt theory in reverse: when seatbelts were introduced, fatalities dropped but accidents went up because drivers felt safer and took more risks. The opposite could be happening here. If a player knows they are playing on turf, they may play more cautiously, which would artificially (no pun intended) make turf look safer than it actually is. I do not have a way to test this with the current data, but it is worth keeping in mind.

On top of that I want to look at rookie and early-career players. My hypothesis going in is that players in their first one to two NFL seasons get injured at higher rates, both because they are physically underprepared for NFL-level contact and because they take on higher-risk roles like special teams. That one I expect to actually show something.

Data source: nflverse via nflreadpy, 2009-2024 regular season. 84,667 player-game observations, just under 15,000 Out designations used as injury proxy. Analysis notebook available on GitHub.