The LabInjuries by playing surface, since 2009
Turf vs Grass
Players have argued about artificial turf for decades. We went to the injury reports. Since 2009, 36,873 new injuries showed up on a report the week after a game, and we matched each one to the surface of that game. Knee, ankle, foot and toe injuries were reported +8% more often after turf games than after grass games (19.1 against 17.7 every 10 team-games), and the serious ones +12% more. Turf came out worse in 15 of 18 seasons. That is a link, not proof that turf caused them: read the three limits below first.
The body map
Where the reports pile up
New injuries per team-game on turf against grass, since 2009. ● = outside the 95% noise band.
↳Bottom lineLower-body injuries are reported +8% more often after turf games (19.1 against 17.7 every 10 team-games), with a clear gap for knee, ankle, foot and heel.
?How to read this chart
- The figure
- colors each body part by how its injury rate on artificial turf compares with natural grass. Green-yellow (lime) = more injuries on turf, blue = more on grass, grey = about even. The stronger the color, the bigger the gap.
- The percentages
- read like this: +20% means that body part gets hurt 20% more often per game on turf than on grass. A ● means the gap is too big to be chance (it stays outside the 95% noise band).
- The bars on the right
- show the raw rates, new injuries every 10 team-games: green striped bar = grass, lime dotted bar = turf. The word "clear" = the same as ●; "within noise" = could be chance.
turf worseevengrass worse
Knee, ankle, foot, toe, Achilles, calf+8%after turf games · 95% range +5% to +12% · 15,635 injuries
The serious ones+12%lower-body injuries that put the player out, doubtful or off the practice field at the first report
Per 10 team-games · grass / turf
Knee+7%clear
Ankle+8%clear
Foot and heel+13%clear
Toe+15%within noise
Achilles−17%within noise
Calf and shin+10%within noise
The rest of the body
Muscles, arms and heads
Strains and upper-body injuries mostly come out even. The head and neck do not: concussions and neck injuries are reported clearly more often after turf games; a harder landing is the usual suspect, though the data cannot confirm it.
↳Bottom lineClear gaps outside the lower body: head and concussion (+11%), neck (+15%). The rest comes out close to even.
?How to read this chart
- One row = one body part
- outside the legs and feet. Green striped bar = injuries every 10 team-games on grass, lime dotted bar = on turf.
- The percentage
- on the right is turf against grass (+ = worse on turf). "Clear" means the gap is too big to be chance; "within noise" means it could be.
Hamstring+2%within noise
Quad and thigh−3%within noise
Groin and hip−2%within noise
Back+7%within noise
Shoulder−6%within noise
Head and concussion+11%clear
Hand and wrist+3%within noise
Elbow and arm+3%within noise
Chest and ribs−4%within noise
Neck+15%clear
Season by season
Turf worse in 15 of 18
Lower-body injuries, turf against grass, each season
↳Bottom lineTurf came out worse in 15 of 18 seasons: one season can swing, the pattern across years is what counts.
?How to read this chart
- One tile = one season.
- The percentage is lower-body injuries on turf against grass that year: +10% means 10% more on turf.
- The fill
- rises with the size of the gap: lime = turf worse, blue = grass worse, grey = about even. A glowing border means that season's gap is clear on its own, not chance.
+6%2009
+12%2010
+6%2011
+17%2012
+9%2013
−2%2014
+10%2015
+14%2016
+12%2017
+18%2018
+2%2019
+0%2020
+2%2021
+2%2022
+11%2023
−2%2024
+18%2025
+18%2026
Who pays
The positions with the biggest gap
Lower-body injuries by position group, turf against grass
↳Bottom lineDL show the biggest gap (+15%), QB least (−8%).
?How to read this chart
- One jersey = one position group,
- sorted from the group turf hurts most to the one it hurts least.
- The percentage
- is lower-body injuries on turf against grass. Underneath: injuries every 10 games on grass → on turf. "Clear" = too big to be chance.
+15%2.8 → 3.2 per 10 games · clear
+13%2.1 → 2.4 per 10 games · clear
+13%3.2 → 3.6 per 10 games · clear
+10%2.4 → 2.6 per 10 games · clear
+5%1.2 → 1.3 per 10 games
+2%1.8 → 1.8 per 10 games
+2%3.5 → 3.6 per 10 games
−8%0.5 → 0.4 per 10 games
The stadium wall
Every home field, on its own surface
Lower-body injuries per team-game for both teams, at each team's current home since 2009 or since it opened
↳Bottom lineMost lower-body injuries: Allegiant Stadium (23.1, grass). Fewest: GEHA Field at Arrowhead Stadium (15.2, grass). Single stadiums are small samples.
?How to read this chart
- One tile = one team's current home field,
- with its surface: striped green background = grass, dotted background = turf.
- The big number
- is lower-body injuries every 10 team-games there, counting both teams. Ranked from most (#1) to fewest. Faded tiles marked "new" have too few games to rank.
#1
Allegiant Stadiumgrass · 100 team-games23.1lower-body / 10#2
NRG Stadiumturf · 148 team-games22.7lower-body / 10#3
Paycor Stadiumturf · 231 team-games22.4lower-body / 10#4
SoFi Stadiumturf · 106 team-games20.4lower-body / 10#5
SoFi Stadiumturf · 100 team-games20.0lower-body / 10#6
Lumen Fieldturf · 268 team-games20.0lower-body / 10#7
Lucas Oil Stadiumturf · 262 team-games20.0lower-body / 10#8
MetLife Stadiumturf · 262 team-games19.5lower-body / 10#9
Hard Rock Stadiumgrass · 260 team-games19.3lower-body / 10#10
Nissan Stadiumgrass · 268 team-games19.3lower-body / 10#11
U.S. Bank Stadiumturf · 156 team-games19.2lower-body / 10#12
Gillette Stadiumturf · 230 team-games18.8lower-body / 10#13
Bank of America Stadiumgrass · 270 team-games18.8lower-body / 10#14
Levi's Stadiumgrass · 186 team-games18.6lower-body / 10#15
Ford Fieldturf · 264 team-games18.6lower-body / 10#16
Caesars Superdometurf · 264 team-games18.6lower-body / 10#17
Mercedes-Benz Stadiumturf · 144 team-games18.3lower-body / 10#18
Huntington Bank Fieldgrass · 270 team-games18.2lower-body / 10#19
State Farm Stadiumgrass · 266 team-games18.0lower-body / 10#20
Northwest Stadiumgrass · 268 team-games17.9lower-body / 10#21
Empower Field at Mile Highgrass · 256 team-games17.7lower-body / 10#22
Lambeau Fieldgrass · 266 team-games17.6lower-body / 10#23
MetLife Stadiumturf · 244 team-games17.5lower-body / 10#24
AT&T Stadiumturf · 272 team-games17.5lower-body / 10#25
M&T Bank Stadiumgrass · 160 team-games17.4lower-body / 10#26
Acrisure Stadiumgrass · 267 team-games17.2lower-body / 10#27
Raymond James Stadiumgrass · 258 team-games17.2lower-body / 10#28
Soldier Fieldgrass · 272 team-games16.7lower-body / 10#29
Lincoln Financial Fieldgrass · 264 team-games16.7lower-body / 10#30
EverBank Stadiumgrass · 254 team-games16.5lower-body / 10#31
GEHA Field at Arrowhead Stadiumgrass · 242 team-games15.2lower-body / 10new
Highmark Stadiumgrass · 8 team-games–too few games
Allegiant Stadiumgrass · 100 team-games23.1lower-body / 10#2NRG Stadiumturf · 148 team-games22.7lower-body / 10#3Paycor Stadiumturf · 231 team-games22.4lower-body / 10#4SoFi Stadiumturf · 106 team-games20.4lower-body / 10#5SoFi Stadiumturf · 100 team-games20.0lower-body / 10#6Lumen Fieldturf · 268 team-games20.0lower-body / 10#7Lucas Oil Stadiumturf · 262 team-games20.0lower-body / 10#8MetLife Stadiumturf · 262 team-games19.5lower-body / 10#9Hard Rock Stadiumgrass · 260 team-games19.3lower-body / 10#10Nissan Stadiumgrass · 268 team-games19.3lower-body / 10#11U.S. Bank Stadiumturf · 156 team-games19.2lower-body / 10#12Gillette Stadiumturf · 230 team-games18.8lower-body / 10#13Bank of America Stadiumgrass · 270 team-games18.8lower-body / 10#14Levi's Stadiumgrass · 186 team-games18.6lower-body / 10#15Ford Fieldturf · 264 team-games18.6lower-body / 10#16Caesars Superdometurf · 264 team-games18.6lower-body / 10#17Mercedes-Benz Stadiumturf · 144 team-games18.3lower-body / 10#18Huntington Bank Fieldgrass · 270 team-games18.2lower-body / 10#19State Farm Stadiumgrass · 266 team-games18.0lower-body / 10#20Northwest Stadiumgrass · 268 team-games17.9lower-body / 10#21Empower Field at Mile Highgrass · 256 team-games17.7lower-body / 10#22Lambeau Fieldgrass · 266 team-games17.6lower-body / 10#23MetLife Stadiumturf · 244 team-games17.5lower-body / 10#24AT&T Stadiumturf · 272 team-games17.5lower-body / 10#25M&T Bank Stadiumgrass · 160 team-games17.4lower-body / 10#26Acrisure Stadiumgrass · 267 team-games17.2lower-body / 10#27Raymond James Stadiumgrass · 258 team-games17.2lower-body / 10#28Soldier Fieldgrass · 272 team-games16.7lower-body / 10#29Lincoln Financial Fieldgrass · 264 team-games16.7lower-body / 10#30EverBank Stadiumgrass · 254 team-games16.5lower-body / 10#31GEHA Field at Arrowhead Stadiumgrass · 242 team-games15.2lower-body / 10newHighmark Stadiumgrass · 8 team-games–too few gamesThe carpet catalogue
Not all turf is the same turf
Lower-body injuries per team-game by surface, 60+ team-games
↳Bottom lineHighest: AstroTurf (20.9). Lowest: AstroPlay (17.0).
?How to read this chart
- One row = one playing surface
- (a grass type or a turf brand) with at least 60 team-games.
- The number
- is lower-body injuries every 10 team-games on that surface.
AstroTurf206 team-games20.9per 10
FieldTurf2,219 team-games19.3per 10
SportTurf518 team-games18.8per 10
Matrix turf434 team-games18.6per 10
A-Turf196 team-games18.2per 10
Natural grass4,839 team-games17.6per 10
AstroPlay122 team-games17.0per 10
Natural experiments
Same team, new surface
Stadiums that changed surface for good
?How to read this chart
- Each card
- is a stadium that changed surface for good: before on the left, after on the right, with the years.
- The numbers
- are lower-body injuries every 10 team-games, both teams, in each period. Same team, same building: the cleanest comparison we have, but still a small sample.
M&T Bank Stadiumturf · 2009-201518.1→grass · 2016-202617.4
Lower-body injuries every 10 team-games, both teams.MethodHow this is built
- What counts as an injury
- A player who appears on a team's official injury report with a body part that was not on the report before the previous game. That injury is credited to the previous game and to its surface. Illness, rest and personal reasons are left out. Source: nflverse injury reports, regular season, 2009 to today.
- What it cannot tell
- The report is a proxy, not a medical record: an injury picked up in practice lands on the game before it, contact and non-contact injuries are mixed, and minor knocks that never reach the report are missed. Practice injuries and missed knocks should hit both surfaces alike, but turf games also differ in roofs, cities, rosters and eras, so the result is an association, not proof that the surface caused the injuries.
- Rates and noise
- Every number is injuries per team-game, so the 4,855 grass team-games and 3,695 turf team-games are compared fairly. The ● mark and the word "clear" mean the 95% interval of the turf to grass ratio stays on one side of even.
- Surfaces
- Surface of each game from nflverse; hybrid grass counts as grass, every synthetic brand as turf. A stadium that changed surface is split into two periods.