Exploring the Associations of Playing Surface and Lower Extremity Injuries Among National Football League Players Restricted; Files Only

Bushnell, Juliana Y. (Spring 2023)

Permanent URL: https://etd.library.emory.edu/concern/etds/qn59q5437?locale=en


Introduction: Lower extremity injuries make up a large proportion of injuries experienced by football players. There is limited literature on the specific role playing surfaces have on injury rates.

Methods: We conducted analyses of the association between playing surfaces and visiting team missed-game lower extremity (LE) injury rates per team game of the 2018-2021 National Football League regular season. Our data included 2,593 LE injuries resulting in at least one missed game. We compared the IRs of playing surface as a binary, trinary, and an eight-level category (artificial turf models and natural grass types specified) variable. Finally, we used a Poisson mixed model with a log link function to estimate the association between playing surface and LE injury rates. This model was selected as our outcome is count data (# of injuries) and it allowed us to control for stadium and club-year as random effects. We ran three versions of this model with our three different surface variables.

Results: For the binary surface variable, the LE injury rate was 1.42 (95% CI 1.31-1.53) and 1.31 (95% CI 1.21-1.40) respectively. When divided into three categories (Artificial sit film, natural grass, other artificial) we found that slit-film had the highest injury rate per team game (1.49 95% CI 1.32-1.65) compared to other artificial (1.36 95% CI 1.22-1.51). When artificial and grass types are specified, A-Turf has the lowest IR (1.07 95% CI 0.69-1.45). Bermuda and Kentucky Bluegrass had an injury rate of 1.30 (95% CI 1.20-1.41) and 1.34 (95% CI 1.10-1.57) respectively. The highest injury rate was UBU/Turfnation  with an IR of 2.04 (95. % CI 1.70-2.39). Our model output also showed that Artificial slit-film has the highest injury rate ratios (1.14 95% CI 0.97-1.32). The two major slit-film models, UBU/TurfNation and MomentumTurf, had the highest IRR’s for the octonary surface model ran (UBU: 1.33 95% CI .92-1.94, MT: 1.31 95% CI 0.91-2.01).

Discussion: In our data, artificial slit-film had the highest injury rates followed by other artificial models then natural grass. We recommend that artificial slit-film be prohibited as a playing surface for both competition and practice fields moving forward. 

Table of Contents

Table of Contents




NFL Demographics

Injury Reporting

Youth Leagues Through College


Injury Location

Playing Surfaces

Natural Grass

“Kentucky” Bluegrass


Tall Fescue

Bermuda Grass


Distribution of field types - NFL

Injury Rates & Turf Type

Limitations and Gaps in Literature




Data Source




Injury Definition

Data Transformation



Model Outcome


Appendix: Figures & Tables


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