Epidemiology of Anterior Cruciate Ligament Tears in the National Football League

Imaging and Surgical Procedures After Surface-Related Collegiate Football Injuries on Artificial Turf Versus Natural Grass: Prevalence and Trends Over 15 Seasons

Background

Few longitudinal studies exist comparing medical procedures after football injuries on artificial and natural grass surfaces.

Purpose/Hypothesis

The purpose of this study was to specifically compare imaging and surgical procedures after surface-related collegiate football injuries on artificial turf versus natural grass. It was hypothesized that there would be no difference in the incidence of imaging and surgical procedures, combined medical procedures, or combined substantial and severe injuries over time between these surfaces.

Study Design

Cohort study; Level of evidence, 2.

Methods

A total of 39 universities across all Football Bowl Subdivision conferences were evaluated over 15 seasons (2006-2020). Playing surfaces evaluated were either a heavyweight artificial turf infill system (≥9.0 lb infill/ft2) or natural grass. Outcomes of interest included medical procedures across injury category, primary injury type, injury location, and specific procedures. Data involved multivariate analyses of variance (MANOVA) and Wilks λ criteria using general linear model procedures and were expressed as medical procedure incidence rates (IRs) per 10-game season.

Results

Overall, 2224 games were documented: 1106 (49.7%) on artificial turf and 1118 (50.3%) on natural grass. Of the 9137 total injuries reported, 4010 (44%) were surface-related cases. MANOVA indicated significant main effects between surfaces according to imaging procedure (F 2,1738 = 4.718; P = .009), surgical procedure (F 1,539 = 5.974; P = .003), and medical diagnosis (F 2,456 = 2.643; P = .040). Post hoc analyses indicated significantly lower (P < .05) incidences on artificial turf versus natural grass, respectively, for the following outcomes: imaging procedures ordered after player-to-surface impact trauma (IR [95% CI], 1.5 [1.3-1.8] vs 2.1 [1.9-2.4]), shoe-to-surface trauma during physical contact (4.4 [4.1-4.7] vs 5.2 [4.9-5.5]), foot injuries (0.6 [0.5-0.7] vs 1.1 [0.9-1.2]), ligament sprains/tears (4.6 [4.3-4.9] vs 5.3 [5.0-5.6]), muscle strains/tears (0.2 [0.2-0.3] vs 0.7 [0.6-0.9]), surgeries performed after shoe-to-surface trauma during physical contact (1.1 [0.9-1.3] vs 1.6 [1.4-1.8]), lower body surgeries (1.8 [1.6-2.0] vs 2.3 [2.1-2.6]), and surgeries involving ligament tears (1.0 [0.9-1.2] vs 1.5 [1.3-1.7]), as well as fewer diagnoses of syndesmosis sprains/tears (0.7 [0.5-0.8] vs 1.0 [0.8-1.2]) and Lisfranc trauma (0.3 [0.2-0.4] vs 0.5 [0.4-0.7]). Trends over the 15 seasons indicated a significant rise in combined medical procedures (P = .005) and combined substantial and severe injuries (P = .0007) irrespective of surface.

Conclusion

Results indicated that collegiate football competition on heavyweight artificial turf resulted in lower incidences of imaging and surgical procedures and medical diagnoses compared with natural grass.

Use of Publicly Obtained Data in Sports Medicine Research: A Systematic Review and Bibliometric Analysis

BACKGROUND

Publicly obtained data (POD) have recently been utilized frequently by sports medicine researchers to describe injury patterns, risk factors, and outcomes in elite athletes. The relative ease of this type of research that is based solely on internet and media sources has resulted in a near exponential increase in the number of these POD studies.

PURPOSE

To systematically review the sports medicine literature for studies based solely on POD.

STUDY DESIGN

Systematic review and bibliometric analysis; Level of evidence, 4.

METHODS

A systematic review of POD studies published since 2000 was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Studies of interest were those relying on publicly available injury reports or online media for data acquisition in collegiate, semiprofessional, and professional athletes.

RESULTS

There were 209 POD studies published between 2000 and 2022, with 173 (82.8%) of these studies published after 2016. Studies were published most frequently on athletes participating in North American professional leagues: National Football League (n = 69 [28.4%]), Major League Baseball (n = 56 [23.0%]), National Basketball Association (n = 37 [15.2%]), and National Hockey League (n = 33 [13.6%]). The most common injuries assessed were head injuries/concussions (n = 43 [21.1%]), anterior cruciate ligament injuries (n = 33 [16.2%]), and ulnar collateral ligament injuries (n = 23 [11.3%]). One-quarter of the studies (n = 53 [25.4%]) reported only 1 POD source, and 1 study (0.5%) reported no source. Additionally, 65 studies (31.1%) listed nonspecific POD resources or solely cited previous literature to describe the POD search methodology and data acquisition.

CONCLUSION

POD studies are exponentially increasing in number, particularly across major North American professional sports leagues, with significant variability in the injury of interest, search methodology, and number of data sources. The accuracy of the conclusions reached based on the POD methodology appears highly variable. Given the potential impact of these publications as both contributors to current knowledge and drivers of future research, the sports medicine community should be aware of the inherent biases and limitations of POD injury studies.

Corticomuscular cross-recurrence analysis reveals between-limb differences in motor control among individuals with ACL reconstruction

Surgical reconstruction of the anterior cruciate ligament (ACL) and subsequent physical therapy can help athletes return to competition; however, re-injury rates remain disproportionately high due, in part, to lingering biomechanical and neurological factors that are not fully addressed during rehabilitation. Prior reports indicate that individuals exhibit altered electrical activity in both brain and muscle after ACL reconstruction (ACLR). In this investigation, we aimed to extend existing approaches by introducing a novel non-linear analysis of corticomuscular dynamics, which does not assume oscillatory coupling between brain and muscle: Corticomuscular cross-recurrence analysis (CM-cRQA). Our findings indicate that corticomuscular dynamics vary significantly between involved (injured) and uninvolved legs of participants with ACLR during voluntary isometric contractions between the brain and both the vastus medialis and lateralis. This finding points to a potential lingering neural deficit underlying re-injury for athletes after surgical reconstruction, namely the dynamical structure of neuromuscular (brain to quad muscle) coordination, which is significantly asymmetric, between limbs, in those who have ACLR.

Does playing surface affect the risk of anterior cruciate ligament injuries in the National Football League? A look at the 2017 - 2021 NFL seasons

BACKGROUND

Anterior cruciate ligament (ACL) injuries are devastating injuries for athletes. Prior studies have shown increased ACL injury rates on non-natural surfaces versus natural grass in several sports. The purpose of this study is to calculate the prevalence of ACL injuries in the NFL on natural versus non-natural surfaces to determine if there is a significant increase on non-natural surfaces.

METHODS

Accessing publicly available data for NFL seasons beginning with the 2017-2018 season through 2021-2022 seasons, all ACL injuries with publicly available data concerning timing and playing surface were recorded and categorized according to playing surface. Practice injuries or those without an identifiable playing surface were excluded. Incidence rates, defined as ACL ruptures per game, were calculated. ACL injuries were recorded for each playing surface, as well as the combined category of non-natural grass surface. Odds ratio was calculated to compare the risk of ACL rupture on non-natural surfaces vs natural grass.

RESULTS

During the 2017-2021 NFL seasons, 173 ACL ruptures were identified with known surfaces. Injury rate for non-natural surfaces was 0.134 compared to 0.097 for grass. Injury rate ratio for non-natural vs natural grass surfaces was 1.211, a 21.1% increased risk of ACL injury in the NFL on non-natural surfaces vs natural grass. OR for non-natural surfaces 1.239 (95% CI 0.900-1.704). Based on these findings there is a trend toward increased risk of ACL injury on non natural grass surfaces, however this did not reach statistical significance.

CONCLUSION

Numerous published studies show trends toward increasing rates of ACL injuries on non-natural playing surfaces vs natural grass. Based on our findings the difference is not statistically significant, however it does trend toward increased risk of ACL injury with non-natural surfaces. Further studies should be performed with larger sample sizes in order to further determine the risk of non-natural surfaces.

Lower hamstring to quadriceps muscle strength ratio and lower body weight as factors associated with noncontact anterior cruciate ligament injury in male American football players: A prospective cohort study

Background

Previous studies have aimed to determine the use of certain risk factors in predicting the occurrence of noncontact anterior cruciate ligament (ACL) injuries. Unfortunately, evidence regarding noncontact ACL injuries in male American football players is limited. This prospective cohort study aimed to identify intrinsic risk factors for noncontact ACL injury among male American football players.

Methods

This study evaluated 152 male American football players in Japan for potential noncontact ACL injury risk factors during a preseason medical assessment, including anthropometric, joint laxity, and flexibility, muscle flexibility, muscle strength, and balance measurements. A total of 25 variables were examined. Participants were monitored during each season for noncontact ACL injury, as diagnosed by physicians.

Results

Noncontact ACL injuries occurred in 11 knees of 11 players (prevalence; 7.1 %). Injured players were significantly more likely to have lightweight (P = 0.049). No statistically significant between-group differences were found for any other variables. Participants with a lower hamstring to quadriceps (H/Q) ratio (P = 0.04) were more likely to sustain noncontact ACL injuries.

Conclusion

Lower H/Q ratio and lower body weight were significantly associated with new-onset noncontact ACL injury in male American football players. These findings will help develop strategies to prevent noncontact ACL injuries in male American football players.

Orthopedic consequences of modern gladiators: a systematic review of lower extremity musculoskeletal issues in retired NFL players

OBJECTIVES

The stressors that National Football League (NFL) athletes face are well-described and documented with regard to multisystem afflictions and injury prevalence. However, the majority of literature discusses the short-term effects rather than long-term outcomes of playing professional football. The purpose of this study was to characterize the long-term musculoskeletal issues in the retired NFL population.

METHODS

Publications from CENTRAL, Scopus, Medline, PubMed, Embase, and Google Scholar were searched from database inception to February 2021. A total of 9 cohort studies evaluating lower extremity arthritis in retired NFL athletes were included for review. Two reviewers extracted data from the individual studies, including demographic information (age, body mass index, length of career, position), injury descriptions (location of injury, number of injuries, diagnoses), and procedure (total knee and or hip arthroplasty) frequency.

RESULTS

Arthritis in retired NFL players was more than twice as prevalent than the general United States male population (95% CI: 2.1-2.3). Ankle osteoarthritis was directly correlated with the number of foot and ankle injuries. Players <50 years of age had a 16.1 and 13.8 times higher risk of undergoing TKA and THA, respectively, when compared to the general population. In older age groups, this trend held with retired NFL players being at least 4.3 and 4.6 times more likely than members of the general population to undergo TKA and THA, respectively.

CONCLUSION

This review demonstrates that the effects of NFL-related lower extremity injuries extend beyond the players' careers and present a higher risk for early-onset osteoarthritis and overall frequency of undergoing total knee and hip arthroplasty.

Anterior Cruciate Ligament Injury Prevention and Rehabilitation

At all levels of American football, knee injuries are common, with injuries to the anterior cruciate ligament (ACL) making up a significant proportion. Historically, ACL injuries were career-altering for professional players, but innovative techniques in surgery and rehabilitation have returned many to the field. While there is a consensus on surgical techniques for ACL reconstruction, significant discrepancies remain on injury prevention and rehabilitation programs. This review article describes the burden of ACL injury on players in the National Football League, best practices in injury prevention and rehabilitation, and evidence-based recommendations for preparing injured athletes to return to play.

Gym-Based Training Interventions for Anterior Cruciate Ligament Injury Reduction in American Football Players

Injuries to the anterior cruciate ligament (ACL) of the knee are one of the most prominent injuries affecting players in American football. One primary aim of training to reduce injury risk is to provide exercises for players on attaining the highest athletic performance with the least orthopedic stress. This review article on ACL injury reduction protocols focuses on the protective and performance-enhancing biomechanical patterns during simple exercises used in a gym-based setting, in the following areas: single-leg balance and trunk stability, single-leg jumping/plyometrics, and reflexive strength training. This supplementary training, as part of a sports performance program, might include training to develop maximum strength, explosive power, acceleration, maximum velocity, bioenergetic endurance qualities, mobility/flexibility, agility, and sport skill acquisition.

Validity of Research Based on Publicly Obtained Data in Sports Medicine: A Quantitative Assessment of Concussions in the National Football League

CONTEXT

Numerous researchers have leveraged publicly available internet sources to publish clinical research concerning incidence and recovery from injuries in National Football League (NFL) players.

OBJECTIVE

This study aims to (1) provide a comprehensive systematic review of all publicly obtained data studies (PODS) regarding concussions in NFL athletes and (2) quantify the percentage of injuries identified by these studies in comparison with published concussion data from the NFL injury database.

STUDY SELECTION

A systematic review was conducted in accordance with PRISMA guidelines to identify all published studies utilizing publicly obtained data regarding concussions in NFL athletes.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Manuscript details, factors related to the athletes of interest (eg, study period, positions included), and results (eg, concussion rate, number of total concussions, return-to-play data) were extracted independently by 2 authors. Results were compared with incident concussions reported from 2015 to 2019 by each medical staff member to the NFL database linked to the League's electronic health record (EHR).

RESULTS

A total of 20 concussion-focused manuscripts based on PODS were identified from 2014 to 2020. PODS captured between 20% and 90% of concussions (mean, 70%) reported by medical staff to the injury database. PODS reported that 55% of concussions occurred on offensive plays, 45% on defensive plays and <1% occurred during special teams plays, compared with 44%, 37%, and 18%, respectively, as indicated by published data from the NFL injury database. When analyzed by position groups, running backs and quarterbacks comprised the most over-represented positions concussed in PODS, while offensive linemen, defensive backs, and linebackers comprised the most under-represented positions.

CONCLUSION

PODS captured approximately 70% of concussions reported by NFL medical staff to the NFL injury database. There is heterogeneity in the degree to which PODS were able to identify concussions, with a bias toward concussions among players at higher profile positions.

MRI Findings Associated With Anterior Cruciate Ligament Tears in National Football League Athletes

Background

Anterior cruciate ligament (ACL) tears are a high-frequency injury requiring a lengthy recovery in professional American football players. Concomitant pathology associated with ACL tears as identified on magnetic resonance imaging (MRI) is not well understood in these athletes.

Purpose

To describe the MRI findings of concomitant injuries associated with ACL tears among athletes in the National Football League (NFL).

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Of 314 ACL injuries in NFL athletes from 2015 through 2019, 191 complete MRI scans from the time of primary ACL injury were identified and reviewed by 2 fellowship-trained musculoskeletal radiologists. Data were collected on ACL tear type and location, as well as presence and location of bone bruises, meniscal tears, articular cartilage pathology, and concomitant ligament pathology. Mechanism data from video review were linked with imaging data to assess association between injury mechanism (contact vs noncontact) and presence of concomitant pathology.

Results

Bone bruises were evident in 94.8% of ACL tears in this cohort, most often in the lateral tibial plateau (81%). Meniscal, additional ligamentous, and/or cartilage injury was present in 89% of these knees. Meniscal tears were present in 70% of knees, lateral (59%) more than medial (41%). Additional ligamentous injury was present in 71% of all MRI scans, more often a grade 1/2 sprain (67%) rather than a grade 3 tear (33%), and most often involving the medial collateral ligament (MCL) (57%) and least often the posterior cruciate ligament (10%). Chondral damage was evident in 49% of all MRI scans, with ≥1 full-thickness defect in 25% of all MRI scans, most often lateral. Most (79%) ACL tears did not involve direct contact to the injured lower extremity. Direct contact injuries (21%) were more likely to have a concomitant MCL tear and/or medial patellofemoral ligament injury and less likely to have a medial meniscal tear.

Conclusion

ACL tears were rarely isolated injuries in this cohort of professional American football athletes. Bone bruises were almost always present, and additional meniscal, ligamentous, and chondral injuries were also common. MRI findings varied by injury mechanism.

Trends in Pediatric Anterior Cruciate Ligament Reconstruction: The Effect of COVID-19

CONTEXT

The number of pediatric anterior cruciate ligament reconstructions (ACLRs) occurring yearly increased almost 6-fold from 2004-2014. We find it interesting that limited recent data exist on rates of ACL injury and reconstruction in children and adolescents, especially in the context of COVID-19.

OBJECTIVE

Given the effect of the COVID-19 pandemic on youth sports seasons and the postponement of many elective surgeries, we sought to examine the changes in rates of ACLR during this period.

DESIGN

Retrospective cohort study.

SETTING

This study used the Pediatric Health Information System (PHIS) database to identify eligible patients at PHIS-participating hospitals nationwide from January 2016-June 2021, with March 1, 2020, considered the start of the COVID-19 pandemic.

PATIENTS OR OTHER PARTICIPANTS

Using Current Procedural Terminology codes, patients 18 years old and younger who underwent ACLR surgery were identified.

MAIN OUTCOME MEASURE(S)

Patient demographics and overall rates of surgery prepandemic and intrapandemic were compared. Data were analyzed using bivariate, mixed-model, and time series analyses.

RESULTS

A total of 24 843 ACLRs were identified during this time period. In total, 1853 fewer surgeries than expected were performed after March 2020 given prepandemic trends. Intrapandemic demographics revealed an increase in the proportion of patients who identified as White and with private insurance and a decrease in the proportion who identified as Black and with public insurance. Also, the proportion of ACLRs by region shifted, with more surgeries performed in the Midwest and fewer in the Northeast. In the model adjusted for hospital-level variability, only race and insurance status remained significant.

CONCLUSIONS

Based on prepandemic trends, fewer patients than projected underwent ACLR once the pandemic began, likely due to a combination of decreased rates of injury and delayed surgery.

Incidence of anterior tibial spine fracture among skiers does not differ with age

PURPOSE

Injury to the anterior cruciate ligament (ACL) is common in alpine skiing in the form of either an intra-substance ACL tear or anterior tibial spine fracture (ATSF). Anterior tibial spine fractures are typically reported in children. However, several case reports describe these injuries in adults while skiing. The purpose of this study is to describe the sport specific incidence of ATSF in alpine skiing.

METHODS

The study was conducted over a 22-year period. Skiers who suffered an ATSF were identified and radiographs were reviewed to confirm the diagnosis. Additionally, control data from intra-substance ACL injury groups were collected. The incidence of these injuries in children, adolescents, and adults (grouped as ages 0-10, 11-16, and 17 + years old, respectively) was evaluated and the risk factors for ATSF versus ACL tear were determined.

RESULTS

There were 1688 intra-substance ACL and 51 ATSF injuries. The incidence of intra-substance ACL injury was greater in adults (40.0 per 100,000 skier days) compared to the adolescent (15.4 per 100,000) and child (1.1 per 100,000) age groups. In contrast, the incidence of ATSF was similar in the adult (0.9 per 100,000), adolescent (1.9 per 100,000), and child (1.9 per 100,000) age groups. Loose ski boot fit was identified as a risk factor for ATSF.

CONCLUSION

The incidence of ATSF in alpine skiers is similar among all age groups. However, the incidence of intra-substance ACL injuries is far greater in adult skiers compared to adolescents and children. Risk factors for ATSF relate to compliance between the foot/ankle and the ski boot.

LEVEL OF EVIDENCE

III.

Effect of COVID-19 on Injury Rates and Timing in the National Football League

Background:

The coronavirus 2019 (COVID-19) pandemic resulted in the cancellation of the 2020 National Football League (NFL) preseason and a decreased preseason roster size. The effect of this disruption on athlete injury rates is unknown.

Purpose/Hypothesis:

The purpose was to quantify the rates of anterior cruciate ligament (ACL), Achilles tendon, and hamstring tendon injuries in NFL players before and after the COVID-19 pandemic. We hypothesized that injury rates in the 2020 season would be higher than those seen prepandemic.

Study Design:

Descriptive epidemiology study. Level of evidence, 4.

Methods:

An online search using publicly available data was carried out to identify all NFL players who sustained an ACL, Achilles tendon, or hamstring tendon injury between April 1, 2017, and March 31, 2021. Data collected included player characteristics as well as career and season of injury workloads.

Results:

The number of Achilles tendon (27 vs 20; P = .024) and hamstring tendon (186 vs 149; P < .001) injuries, respectively, in the 2020 NFL season were significantly higher than the average of the 2017 to 2019 seasons. However, the number of ACL injuries sustained remained constant (43 vs 46; P = .175). More than half (52.9%) of ACL injuries in the 2017 to 2019 seasons occurred in the preseason, while most of the injuries (34.9%) in the 2020 season occurred in weeks 1 to 4. There was no player characteristic or career workload variable collected that was significantly different for players who sustained an ACL, Achilles tendon, or hamstring tendon injury in the 2020 NFL season compared with the 2017 to 2019 seasons.

Conclusion:

In the 2020 NFL season, the number of Achilles tendon and hamstring tendon injuries rose while the number of ACL injuries remained constant compared with the 2017 to 2019 seasons. Injuries that occurred during the first 4 games of the 2020 NFL season were consistent, with higher rates of injuries seen in the preseason in previous years.

ACL Tears in the National Football League From 2013 to 2020: Analysis of the 2020 Season After Delays and Schedule Changes From the Early COVID-19 Pandemic Relative to Prior Seasons

Background:

The impact of fatigue and preseason preparation on anterior cruciate ligament (ACL) tears in the National Football League (NFL) are not well described. The 2020 NFL season did not include the standard preseason in response to changes secondary to the coronavirus disease-2019 (COVID-19) pandemic.

Purpose:

To evaluate the association of game play on ACL tears in NFL athletes and to determine if differences in ACL tear epidemiology were present based on season of play from 2013 to 2020.

Study Design:

Descriptive epidemiology study.

Methods:

ACL tears in NFL athletes were identified using publicly available data. Games played and snap counts at the time of injury were recorded for each athlete sustaining game-related injuries. Tear rates were determined, and injuries were also calculated per 1000 athlete-exposures. Incidence rate ratios (IRRs) with 95% confidence intervals (CIs) were calculated.

Results:

Overall, 379 ACL tears were identified, including 256 (67.6%) during game play and 118 (31.1%) during practice. Practice-based injuries were significantly higher in the preseason versus the remainder of the season. Games and snaps at the time of injury did not differ by year. The incidence rate of preseason injuries was significantly greater relative to in-season injuries (IRR = 2.68; 95% CI, 2.18-3.29; P < .00001). There was an elevated incidence rate of in-season injuries in 2020 relative to 2014-2019 combined (IRR = 1.49; 95% CI, 0.98-2.19; P = .048). In 2013 to 2019, the most frequent month of injury was the first month of the preseason in August (119/334 tears; 35.6%), whereas in 2020, the most frequent month was September (13/41 tears, 31.7%). The proportion of tears in September 2020 was not different from the proportion of tears in August 2013 to 2019.

Conclusion:

There was an increased proportion of in-season ACL tears in the 2020 NFL season relative to 2014 to 2019; this is attributable to a frameshift in the consistent trend of injuries in the 1st month to return of competitive play, with 2020 being in the regular season in September as opposed to the preseason in August.

Factors Associated With the Mechanism of ACL Tears in the National Football League: A Video-Based Analysis

Background

The factors associated with anterior cruciate ligament (ACL) injury mechanism in professional American football players are not well-understood.

Hypothesis

It was hypothesized that football-related and player-specific factors, such as position and body mass index (BMI), are associated with ACL injury mechanism in these athletes.

Study Design

Descriptive epidemiology study.

Methods

Videos of ACL tears occurring in National Football League (NFL) games over 6 consecutive seasons from 2014 to 2019 were reviewed by 2 orthopaedic surgeons who specialize in sports medicine. For each injury, the role of contact (direct contact [contact to the injured knee/lower extremity], indirect contact [contact not involving the injured knee/lower extremity], or no contact) as well as playing situation and lower extremity position were recorded. Additional player characteristics, timing of injury, and surface information were obtained from NFL game-day and injury database statistics.

Results

Of the 140 ACL tears, a minority occurred via direct contact to the injured lower extremity (30%), although this varied by position. Just over two-thirds (70%) of ACL tears in offensive linemen occurred via direct contact to the injured lower extremity, while wide receivers had no direct contact ACL tears. Elevated BMI was associated with a greater likelihood of ACL tears occurring via direct contact (53% in players with BMI ≥35 kg/m² vs 24% in players with BMI <35 kg/m²; P = <.01). Rookies had the lowest percentage of direct contact ACL tears (18%; P = .22). ACL tears that occurred during the middle 8 weeks of the regular season resulted more often from direct contact (38%; P = .06). ACL tears that occurred in the third quarter were the most likely to occur via direct contact (44%), while those that occurred in the fourth quarter were the least likely to occur via direct contact (13%; P < .01).

Conclusion

Although most NFL players sustained ACL tears via a noncontact mechanism (ie, through indirect or no contact), players with an elevated BMI, especially on the offensive line, were more likely to injure their ACL through direct contact. Position-dependent variance in injury mechanism may help guide injury prevention efforts in these athletes.