Ground Truth: Grass Versus Turf Misses the Point
Just before the 2026 World Cup, eleven NFL stadiums tore out their artificial turf and laid natural grass, because FIFA requires it. Seven of them are now tearing the grass back out and reinstalling turf for the football season (at a cost that often runs upwards of seven figures per stadium).
NFL players noticed. Within days of the final, dozens of them flooded social media with a single hashtag, #WorthTheCost, arguing that if grass is good enough for the World Cup, it's good enough for them.¹
From where we’re watching: whichever way that argument resolves, athletes will still plant, cut, and land on whatever surface is under them that day. That's the part we're interested in.
The debate over grass versus turf treats the surface as the problem, when the surface is only one input into something more fundamental: the forces that perturb the joint when a foot plants, twists, or lands. A few weeks earlier, players at Wimbledon were slipping on grass and rolling ankles on it. Grass. The surface all the NFL players are asking for. That should tell you that the answer isn't on the surface.
What a surface actually is
A playing surface isn't one thing. It's a bundle of characteristics — how much it grips, how much it gives, how much energy it returns, and how all of that shifts with heat, moisture, and wear. When a controlled study put five cleat patterns across two artificial surfaces and two natural grass systems, both artificial surfaces produced significantly higher peak torque and rotational stiffness than the grass.² When other researchers measured the release properties of a shoe on a surface across changing ambient temperature, the numbers moved with the weather.³ A surface is not a static object an athlete steps onto. It's a variable that changes by the hour.
This is where the grass-versus-turf framing tends to oversimplify. "Grass" in cool, wet conditions and "grass" baking under a closed stadium roof are not the same surface, mechanically. Neither are two turf fields of different make, infill, and age.
Shifting focus: the interface
The risk to a joint doesn't come from the surface alone, or the shoe alone. It comes from the interface between them — the specific combination of cleat, surface, and conditions at the moment of contact.
The mechanism has been understood in outline for a long time: when the foot grips the ground harder than the situation calls for, it can "fix" in place while the body keeps rotating over it, sending torque up into the ankle and knee.⁴ The more rotational grip at that interface, the more of that load the joint absorbs. One study followed 555 high school football players for three years, measuring each athlete's actual footwear traction on the actual field, then tracking their injuries. As rotational traction climbed from low to high, the noncontact lower-extremity injury rate rose steadily, from 4.2 to 19.2 injuries per 1,000 game exposures.⁵
That study also found something less tidy. Translational traction didn't follow the same clean upward line — injury rate peaked in the middle of the range and then fell off at the high end.⁵ Grip and injury don't relate as simply as "more is worse." The interface is a system, and it doesn't reduce to a single dial you can turn down.
So does turf hurt people more than grass?
The honest answer is that the best available evidence doesn't agree with itself.
A 2022 systematic review of 53 studies concluded that overall and knee injury rates were broadly similar across the two surfaces, but that foot and ankle injuries occurred at a higher rate on turf.⁶ A 2023 systematic review and meta-analysis — the first to statistically pool the football-specific data — reached a different conclusion: overall injury incidence roughly 14% lower on turf, with no injury category showing elevated risk on turf, including the foot and ankle.⁷ The 2023 authors addressed the earlier review directly, noting that its foot-and-ankle conclusion came from counting studies rather than pooling their data, which they argued weakened it.⁷
Two rigorous reviews, opposite headlines. And notably, even the one that favored turf graded its own certainty as low, because only 5 of its 22 included studies controlled for confounding variables at all.⁷ The confounders those authors flagged as usually missing? Weather, pitch wetness, and the type of stud the athlete was wearing.⁷
So where does this leave us? The single biggest weakness in the surface-injury literature is that it mostly fails to account for the interface — the grip, the conditions, the footwear — which is the thing that actually loads the joint. The studies argue about the surface while the variable that matters slips through the gaps between them. (The picture gets no cleaner in subgroups: one 2022 meta-analysis found elevated ACL risk for female soccer players on turf, which the 2023 pooled analysis did not reproduce.⁸)
Why players and data disagree
None of this means the players are wrong to want grass. Athletes overwhelmingly prefer grass and report that it feels better on their bodies, even where aggregate injury data can't cleanly confirm a difference.⁷ Perceived load, fatigue, and confidence are real and they matter, and they're not always visible in an injury-rate table. However, this brings to light a genuine gap: either the players are registering something the studies haven't captured, or they aren't — and the current evidence can't tell us which.
The question we'd rather ask
Step back from the debate and a different question comes into focus. Which surface is safer may never be settled, and on any given day, in any given stadium, it's largely outside the athlete's control anyway. The surface is what it is when they walk out onto it.
What isn't fixed is what happens when the athlete gets moving. The interface sets the loading environment; the joint is where the bill comes due, whatever the athlete is standing on. That's the variable worth working on — not litigating the ground, but understanding what the forces at the point of contact actually look like, and responding to them where they arrive.
LigaSys is developing Smart Ligament™ systems — reactive wearable hardware designed to sense dangerous joint motion and respond mechanically in real time. If you're working on athlete availability and performance outcomes, we'd like to hear from you.
References
Front Office Sports. NFLPA uses World Cup final to renew push for grass fields in stadiums. July 2026. https://frontofficesports.com/nflpa-uses-world-cup-final-to-renew-push-for-grass-fields-in-stadiums/
Villwock MR, Meyer EG, Powell JW, Fouty AJ, Haut RC. Football playing surface and shoe design affect rotational traction. American Journal of Sports Medicine. 2009;37(3):518–525. https://pubmed.ncbi.nlm.nih.gov/19168808/
Torg JS, Stilwell G, Rogers K. The effect of ambient temperature on the shoe-surface interface release coefficient. American Journal of Sports Medicine. 1996;24(1):79–82. https://pubmed.ncbi.nlm.nih.gov/8638757/
Torg JS, Quedenfeld TC, Landau S. The shoe-surface interface and its relationship to football knee injuries. Journal of Sports Medicine. 1974;2(5):261–269. https://pubmed.ncbi.nlm.nih.gov/4468345/
Wannop JW, Luo G, Stefanyshyn DJ. Footwear traction and lower extremity noncontact injury. Medicine & Science in Sports & Exercise. 2013;45(11):2137–2143. https://pubmed.ncbi.nlm.nih.gov/23657169/
Gould HP, Lostetter SJ, Samuelson ER, Guyton GP. Lower extremity injury rates on artificial turf versus natural grass playing surfaces: a systematic review. American Journal of Sports Medicine. 2022;50(6):1615–1621. https://pubmed.ncbi.nlm.nih.gov/35593739/
Kuitunen I, Immonen V, Pakarinen O, Mattila VM, Ponkilainen VT. Incidence of football injuries sustained on artificial turf compared to grass and other playing surfaces: a systematic review and meta-analysis. eClinicalMedicine. 2023;59:101956. https://pubmed.ncbi.nlm.nih.gov/37125402/
Xiao M, Lemos JL, Hwang CE, Sherman SL, Safran MR, Abrams GD. Increased risk of ACL injury for female but not male soccer players on artificial turf versus natural grass: a systematic review and meta-analysis. Orthopaedic Journal of Sports Medicine. 2022;10(8). https://pubmed.ncbi.nlm.nih.gov/35990873/
