1 Introduction

Ankle injuries represent 10–28% of all sports-related traumas, and can cause lingering problems for athletes.^1,2 Pain and instability are the most prevalent concerns, followed by crepitus, weakness, stiffness, and swelling.² The nature of the residual problems can also depend on injury frequency. For ankles sprained under and over 5, the primary concerns are pain and instability, respectively.² Patients who sustain an inversion ankle injury during sports experienced persistent symptoms for at least two years after the initial injury.³ Additionally, ankle injuries have been associated with altered proprioception, further affecting athlete performance and recovery.⁴

American football is one of the most high-risk sports in the United States.⁵ Players in offensive positions and “skill positions” are especially vulnerable to foot and ankle injuries due to the intense force and torque exerted on the distal extremities during actions like running, cutting, and tackling.^6–8 Offensive linemen, running backs, and tight ends exhibit higher overall rates of ankle injuries, while special teams players demonstrate the lowest incidence.^6,7

Despite the significant impact of ankle injuries in the NFL, no studies have evaluated the effects of these injuries on football performance in terms of fantasy football output.⁹ Fantasy football points are an underutilized resource for this purpose, as they combine many aspects of a player's performance into a single representative value that facilitates comparison. Our study utilizes fantasy football points as a proxy measure for offensive skill player performance after ankle injury.¹⁰ We hypothesize that fantasy points will reflect decreases in player performance.

2 Methods

3 Results

3.2

3.2 Overall performance metrics

Offensive skill players who sustained ankle injuries during the study period showed statistically significant decreases in number of games played, average fantasy points scored per game (PPG), and total fantasy points in the season after their injury. The matched controls did not show statistically significant decreases in these measures. These results are detailed in Table 1. Factoring in RTP and injury type as covariates did not significantly impact average fantasy PPG and total fantasy points per season. However, including RTP as a covariate when analyzing number of games played in the seasons before and after the ankle injury increased the P value from <0.0001 to 0.0127. Similarly, including injury type as a covariate increased the P value from <0.0001 to 0.132. This indicates that RTP time and injury type could have confounding influences on the number of games played in the season following an ankle injury. These results are detailed in Table 2. Post-hoc Bonferroni adjustments showed no significant differences between the different injury types and their respective impacts on number of games played, PPG, or total points after the player's ankle injury. The changes in fantasy points before and after a player's ankle injury are summarized in Fig. 1.

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Fig. 1 Change in fantasy points per game and total fantasy points before and after an ankle injury. * Indicates p ≤ 0.05, n.s. Indicates a lack of statistical significance.

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4 Discussion

In this study of 303 ankle injuries that occurred over the course of 11 NFL seasons, we found that injured NFL players exhibit significant detriments in fantasy football production in the year following their ankle injury. When stratifying by player position, we found that route runners show significantly impaired fantasy football production across all metrics studied, compared to quarterbacks, whose performance is generally unaffected. These results support those of previous analyses of fantasy output following lower extremity injury.¹⁶ Our findings not only display an interesting injury pattern, but are also clinically relevant. Athletes, coaches, team medical staff, and athletic trainers may use these results to guide clinical decision-making with regard to return-to-play timing, rehabilitation protocols, and enhanced prevention strategies for athletes with ankle injuries, with the aim of mitigating the decrease in post-injury performance noted in our study.

Previous studies have identified ankle injuries as one of, if not the most common musculoskeletal injury sustained by football players.^8,14,17 In fact, a study of players attending the NFL combine showed that 53.2% of players had a previous ankle injury, even before the player enters the NFL.⁶ The prevalence of ankle injuries in NFL players poses a particular challenge in light of evidence that these injuries have consistently been shown to impact players long-term.¹⁴ After ankle injuries, football players are likely to experience persistent symptoms, especially stiffness, and can develop chronic ankle instability (CAI).¹⁸ CAI is characterized by laxity and mechanical instability, leading to insufficiency of the lateral ankle ligament complex that interferes with activity.¹⁹ Onset of CAI can occur after just one ankle sprain and worsens with repetitive injuries, which is concerning when considering that 43% of acute ankle sprains reported in football players are recurrent injuries.²⁰ An explanation for this trend is that ankle sprains are most often reported in sports characterized by motions such as running, cutting, and jumping: motions that are integral to offensive football players moving the ball downfield.²⁰ Route runners run with the ball, cut to evade defensive opponents, and jump to catch thrown balls. Considering the integral biomechanical role of the ankle in running football routes, our findings that route runners exhibit decreased performance in every metric during the season following an ankle injury are well-supported.

We found that quarterbacks did not exhibit the same decrease in performance in the season following an ankle injury that was observed in route runners. These results support previous literature that have also concluded not only that ankle injuries are less frequent in quarterbacks, but also that they do not significantly impact quarterback performance.^14,21 Ankle injuries have the potential to limit quarterbacks’ pocket mobility and rushing efficacy, however, these skills are not critical for quarterback performance.¹⁴

Surprisingly, adjusting for RTP time and injury type did not affect the decreases observed in PPG and total fantasy points. However, they did both exert a confounding effect on the number of games in which the athlete played in the season following their ankle injury, given that increased RTP time and more severe injuries could sideline players continuing into the following season. The fact that players still exhibit significant decreases in fantasy points regardless of ankle injury severity may point to the effectiveness of rehabilitation programs within the NFL. Conversely, because players with longer RTP time and more severe injuries may be sidelined for a period spanning more than one season, it is logical that these factors would exert a confounding effect on the number of games in which that player participates during the season following their ankle injury.

This study should be interpreted in the context of its limitations. Firstly, as this a retrospective study, we can only report associations, not causation. We lacked access to the NFL electronic medical record. Fantasy football points are not a previously validated performance measure. While the on-field components that comprise fantasy football points are direct performance statistics, they are differentially weighted within the fantasy score, therefore some extrapolation is pertinent while interpreting the results. There are inherent limitations that come with using a public injury database, including under- or over-reporting of injuries based solely on media reports. Some injuries in the Pro Football Reference database were classified as “other”, which could contribute to an undercounting of ankle injuries. This study did not account for ankle injuries sustained prior to the inception of the study period. The Pro Football Reference database does not include information about mechanism of injury, such as contact or non-contact, nor information about playing conditions that could influence injury risk, so those factors were not included in our analysis.

5 Conclusion

Over the course of eleven NFL seasons, there were 332 ankle injuries sustained by offensive skill players. Fantasy output, measured in terms of both average points scored per game and total season points, decreased significantly during the season following an ankle injury. This finding was not influenced by RTP, type of ankle injury, BMI, or player age. Route runner positions experienced significant decreases across all performance metrics evaluated, while quarterbacks did not show notable decreases in specific performance metrics. These results confirm prior studies showing the harmful impact of ankle injuries in football players. Further research should examine NFL rehabilitation protocols, and how they can be optimized to improve player performance upon their return from an ankle injury.

Declaration of competing interest

The authors declare no conflicts of interest. Ethical approval was not sought for the present study because all data was obtained from a publicly available database.

Ethics

This study was a retrospective review of an open-access, online database. Because the database is compiled via publicly available media reports and does not contain specific medical information, Institutional Review Board approval was not necessary.

Financial statement

No financial support was procured or received for the publication of this article.

Guardian/Patient's consent

Not applicable, no identifiable human subjects.

CRediT authorship contribution statement

Victoria E. Bergstein: Methodology, Formal analysis, Investigation, Data curation, Writing – original draft, Writing – review & editing, Visualization, Project administration. Amy Z. Lu: Investigation, Data curation, Writing – original draft, Writing – review & editing. Blake H. Hodgens: Writing – review & editing. Blake M. Bodendorfer: Writing – review & editing. Steven F. DeFroda: Writing – review & editing. Jonathan Kaplan: Writing – review & editing. Amiethab A. Aiyer: Writing, Conceptualization, Writing – review & editing, Supervision.