Acute Gastrocnemius-Soleus Complex Injuries in National Football League Athletes

Lower Extremity Strains in the US National Football League, 2015-2019

BACKGROUND

Lower extremity (LEX) strains, including hamstring, quadriceps, adductor, and calf strains, are among the most common injuries in sports. These injuries lead to high burden, resulting in significant missed participation time.

PURPOSE

To describe the incidence of LEX strains in professional American football.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

This study included all players who played in ≥1 National Football League (NFL) game or sustained a LEX strain during participation in the 2015-2019 seasons. LEX strain frequency was calculated by setting (game, practice, conditioning), timing in season (offseason, preseason, regular season, postseason), and roster position. Game incidence rates were calculated for season, roster position, and play type. LEX strains were identified in the standardized leaguewide electronic health record (n = 32 teams).

RESULTS

Across 5 years, 5780 LEX strains were reported among 2769 players (1-year risk, 26.7%; 95% CI, 26.0%-27.3%); 69% (n = 4015) resulted in time loss. Among all LEX strains, 54.7% were hamstring (n = 3163), 24.1% adductor (n = 1393), 12.6% calf (n = 728), 8.3% quadriceps (n = 477), and 0.3% multiple muscle groups (n = 19). Most were reported during preseason practices (n = 1076; 27%) and regular season games (n = 1060; 26%). The 2-week period of training camp practices comprised 19% of all time-loss strains. Among game injuries, preseason games had the highest rate of LEX strain (2.9/10,000 player-plays; 95% CI, 2.6-3.2). Defensive secondary players accounted for the highest proportion of time-loss LEX strains (27%; n = 1082). In games, punt plays had nearly twice the injury rate of kickoff plays (14.9/1000 plays [95% CI, 13.1-17.0] vs 7.5/1000 plays [95% CI, 6.2-8.9], respectively) and >3 times the rate of pass plays (4.3/1000 plays; 95% CI, 4.0-4.7) and run plays (2.6/1000 plays; 95% CI, 2.3-2.9). In aggregate, LEX strains led to an estimated 16,748 participation days missed each year and a median 12 days missed per injury.

CONCLUSION

LEX strains affected 1 in 4 NFL players each year, resulting in a high burden of injury in terms of time lost from practice and competition. Safe return to the NFL season during training camp and reduction of injuries during regular season games are key focuses for future injury reduction.

Normative isometric plantarflexion strength values for professional level, male rugby union athletes

OBJECTIVES

The primary aim was to establish normative values of isometric plantarflexor muscle strength in professional male rugby union players and compare forwards with backs. The secondary aims were to examine how individual playing position or age influences isometric plantarflexor strength.

DESIGN

Cross-sectional.

SETTING

Testing at professional rugby clubs.

PARTICIPANTS

355 players (201 forwards and 154 backs) from 9 clubs in the English Premiership club competition.

MAIN OUTCOME MEASURES

Maximal unilateral isometric plantarflexion strength was measured, using a Fysiometer C-Station, in a seated position with a flexed knee and in maximal available dorsiflexion. Values are reported normalised to body mass and specific to playing position.

RESULTS

Mean combined limb isometric plantarflexion strength for the group was 193.1 kg (SD 32) or 1.86 xBW. (SD 0.31). Forwards were significantly weaker than backs (forwards = 1.75xBW (SD 0.26), backs = 2.00xBW (SD 0.28) (p=<0.0001)). Age category revealed no influence on plantarflexor strength.

CONCLUSION

This study presents normative isometric plantarflexion strength values for professional male rugby union players. Forwards are typically relatively weaker than backs.

The Assessment, Management and Prevention of Calf Muscle Strain Injuries: A Qualitative Study of the Practices and Perspectives of 20 Expert Sports Clinicians

Background

Despite calf muscle strain injuries (CMSI) being problematic in many sports, there is a dearth of research to guide clinicians dealing with these injuries. The aim of this study was to evaluate the current practices and perspectives of a select group of international experts regarding the assessment, management and prevention of CMSI using in-depth semi-structured interviews.

Results

Twenty expert clinicians working in elite sport and/or clinician-researchers specialising in the field completed interviews. A number of key points emerged from the interviews. Characteristics of CMSI were considered unique compared to other muscle strains. Rigor in the clinical approach clarifies the diagnosis, whereas ongoing monitoring of calf capacity and responses to loading exposure provides the most accurate estimate of prognosis. Athlete intrinsic characteristics, injury factors and sport demands shaped rehabilitation across six management phases, which were guided by key principles to optimise performance at return to play (RTP) while avoiding subsequent injury or recurrence. To prevent CMSI, periodic monitoring is common, but practices vary and data are collected to inform load-management and exercise selection rather than predict future CMSI. A universal injury prevention program for CMSI may not exist. Instead, individualised strategies should reflect athlete intrinsic characteristics and sport demands.

Conclusions

Information provided by experts enabled a recommended approach to clinically evaluate CMSI to be outlined, highlighting the injury characteristics considered most important for diagnosis and prognosis. Principles for optimal management after CMSI were also identified, which involved a systematic approach to rehabilitation and the RTP decision. Although CMSI were reportedly difficult to prevent, on- and off-field strategies were implemented by experts to mitigate risk, particularly in susceptible athletes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-021-00364-0.

Lower Extremity Muscle Injuries in the Overhead Athlete

PURPOSE OF REVIEW

Lower extremity (LE) injuries are a common source of disability and time-loss for overhead athletes, and muscles have been found to be the predominant soft tissue structure affected. The current review highlights the orthopaedic literature examining lower extremity muscle injuries in overhead athletes in regard to epidemiology, diagnosis, and conventional and emerging treatment measures.

RECENT FINDINGS

The hamstring muscles have been found to be the most commonly injured lower extremity muscle group in professional baseball, followed by the adductors, quadriceps, iliopsoas, and gastrocnemius-soleus complex. Strains and contusions comprise over 90% of these muscle injuries. Various advanced imaging grading systems have been developed to help characterize the nature of a muscle injury, although a clear and consistent prognostic utility of these systems is still unclear. The vast majority of lower extremity muscle injuries in overhead athletes are managed nonoperatively, and there is promising data on the use of emerging treatments such as platelet-rich plasma and blood flow restriction therapy. Lower extremity muscle injuries-often referred to as strains-are a relatively common issue in high-demand overhead athletes and can be a significant source of time-loss. Within baseball, position players are affected far more often than pitchers, and sprinting and fielding are the most common activities leading to strains. Magnetic resonance imaging (MRI) is considered the gold standard imaging modality to evaluate these muscle injuries and will allow for a detailed assessment of tissue damage. Nonetheless, return-to-play is often dictated by a given athlete's progression through a nonoperative rehabilitation protocol, with surgical intervention reserved for less common, select injury patterns.

Machine Learning for Predicting Lower Extremity Muscle Strain in National Basketball Association Athletes

Background

In professional sports, injuries resulting in loss of playing time have serious implications for both the athlete and the organization. Efforts to quantify injury probability utilizing machine learning have been met with renewed interest, and the development of effective models has the potential to supplement the decision-making process of team physicians.

Purpose/Hypothesis

The purpose of this study was to (1) characterize the epidemiology of time-loss lower extremity muscle strains (LEMSs) in the National Basketball Association (NBA) from 1999 to 2019 and (2) determine the validity of a machine-learning model in predicting injury risk. It was hypothesized that time-loss LEMSs would be infrequent in this cohort and that a machine-learning model would outperform conventional methods in the prediction of injury risk.

Study Design

Case-control study; Level of evidence, 3.

Methods

Performance data and rates of the 4 major muscle strain injury types (hamstring, quadriceps, calf, and groin) were compiled from the 1999 to 2019 NBA seasons. Injuries included all publicly reported injuries that resulted in lost playing time. Models to predict the occurrence of a LEMS were generated using random forest, extreme gradient boosting (XGBoost), neural network, support vector machines, elastic net penalized logistic regression, and generalized logistic regression. Performance was compared utilizing discrimination, calibration, decision curve analysis, and the Brier score.

Results

A total of 736 LEMSs resulting in lost playing time occurred among 2103 athletes. Important variables for predicting LEMS included previous number of lower extremity injuries; age; recent history of injuries to the ankle, hamstring, or groin; and recent history of concussion as well as 3-point attempt rate and free throw attempt rate. The XGBoost machine achieved the best performance based on discrimination assessed via internal validation (area under the receiver operating characteristic curve, 0.840), calibration, and decision curve analysis.

Conclusion

Machine learning algorithms such as XGBoost outperformed logistic regression in the prediction of a LEMS that will result in lost time. Several variables increased the risk of LEMS, including a history of various lower extremity injuries, recent concussion, and total number of previous injuries.

Test-Retest Reliability of the Isometric Soleus Strength Test in Elite Male Academy Footballers

BACKGROUND

Currently there is no reliability data available for the isometric soleus strength test (ISST), commonly used as a monitoring tool in elite football settings. Isometric strength testing for other muscle groups, most notably the hamstrings, is utilized to identify injury risk and readiness to train/play. To profile athletes efficiently, performance practitioners require optimal measures that are reliable. The aim of this study was to investigate the test-retest reliability of the isometric strength test of the soleus and propose a standardized protocol for its use within an elite male football population.

STUDY DESIGN

Test-retest reliability single cohort study.

METHODS

Thirty elite male footballers (age = 22.8±5.0 years, height = 180.0±0.08 cm, weight = 70.57±4.0 kg) performed the ISST, through three maximum 3-second hold efforts with one minute rest between repetitions and 48 hours between tests, in each test. The test was performed mid-competitive season. All data bilaterally were checked for normality using the Shapiro-Wilk test before a Pearson's Correlations and Bland-Altman's analyses were performed.

RESULTS

Test-retest reliability demonstrated high reliability for ISST bilaterally (Right: r = 0.89; Left: r = 0.79, p<0.05). The standard error of measurement (SEM) (%) was 9.09 - 12.47% and minimal detectable change (MDC) was 25.19 - 34.56 (N) for Peak Force (PF) measures of the ISST. Bilateral levels of agreement were found to be +/- 2 standard deviations (SD) of the interval of agreement bilaterally for ISST (Levels of agreement (LOA): Right: Upper 352.49 - Lower -494.76; Left: Upper 523.82 - Lower -591.30. Bilaterally no significant difference was detected between values (Right: p=0.09, CI: -153.21-10.95; Left: p=0.52, CI: -139.81-72.33).

CONCLUSION

The results of this study demonstrate high reliability for the ISST. The ISST displays a high test-retest reliability for assessing PF characteristics of the soleus in elite male academy footballers. This test may be beneficial for performance practitioners for profiling soleus function of athletes.

Return to play protocols for musculoskeletal upper and lower limb injuries in tackle-collision team sports: A systematic review

Athletes in tackle-collision teams are at high risk of musculoskeletal injuries resulting in absence from play due to the high impact nature of the sport. There is a paucity of research to guide the management and assessment methods needed to facilitate the return to play (RTP) process. This review aimed to describe, synthesise and evaluate RTP protocols implemented for musculoskeletal injuries in tackle-collision teams. A systematic search of Scopus, PubMed, Web of Science and Ebsco Host was conducted for RTP management protocols and assessment modalities following upper and lower limb musculoskeletal injuries in tackle-collision team athletes. Prospective and retrospective quantitative controlled trials, cohort, case-control, case-series and cross-sectional observation studies published between January 2000 and March 2020 were considered. The main outcome measures were the proportion of athletes to RTP, associated time-loss and reinjury risk. 5265 articles were screened. 34 studies met the eligibility criteria of which 23 involved management and 11 assessment modalities. Management involved surgical or conservative strategies along with exercise-based rehabilitation. Assessment modalities included radiographic assessment, clinical evaluation and subjective ratings. Promising RTP management included progressive weight-bearing and exercised-based rehabilitation for ankle sprains as well as surgery, the use of a sling and exercise-based rehabilitation for shoulder instability. MRI scans showed promise in predicting time-loss following hamstring and calf strains in tackle-collision athletes. There are currently no clear guidelines for RTP after musculoskeletal injuries in tackle-collision sports. Future research should investigate efficient management strategies evaluated through valid and reliable assessment methods to better guide clinicians.

Eccentric Strength Assessment of Hamstring Muscles with New Technologies: a Systematic Review of Current Methods and Clinical Implications

BACKGROUND

Given the severe economic and performance implications of hamstring injuries, there are different attempts to identify their risk factors for subsequently developing injury prevention strategies to reduce the risk of these injuries. One of the strategies reported in the scientific literature is the application of interventions with eccentric exercises. To verify the effectiveness of these interventions, different eccentric strength measurements have been used with low-cost devices as alternatives to the widespread used isokinetic dynamometers and the technically limited handheld dynamometers. Therefore, the purpose of the present systematic review was to summarize the findings of the scientific literature related to the evaluation of eccentric strength of hamstring muscles with these new technologies.

METHODS

Systematic searches through the PubMed, Scopus, and Web of Science databases, from inception up to April 2020, were conducted for peer reviewed articles written in English, reporting eccentric strength of hamstrings assessed by devices, different to isokinetic and handheld dynamometers, in athletes.

RESULTS

Seventeen studies were finally included in the review with 4 different devices used and 18 parameters identified. The pooled sample consisted of 2893 participants (97% male and 3% female: 22 ± 4 years). The parameters most used were peak force (highest and average), peak torque (average and highest), and between-limb imbalance (left-to-right limb ratio). There is inconsistency regarding the association between eccentric hamstrings strength and both injury risk and athletic performance. There is no standardized definition or standardization of the calculation of the used parameters.

CONCLUSIONS

The current evidence is insufficient to recommend a practical guide for sports professionals to use these new technologies in their daily routine, due to the need for standardized definitions and calculations. Furthermore, more studies with female athletes are warranted. Despite these limitations, the eccentric strength of hamstring muscles assessed by different devices may be recommended for monitoring the neuromuscular status of athletes.

Return to Play and Recurrence After Calf Muscle Strain Injuries in Elite Australian Football Players

BACKGROUND

Calf muscle strain injuries (CMSI) are prevalent in sport, but information about factors associated with time to return to play (RTP) and recurrence is limited.

PURPOSE

To determine whether clinical and magnetic resonance imaging (MRI) data are associated with RTP and recurrence after CMSI.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Data of 149 CMSI reported to the Soft Tissue injury Registry of the Australian Football League were explored to evaluate the impact of clinical data and index injury MRI findings on RTP and recurrence. Clinical data included age, previous injury history, ethnicity, and the mechanism of injury.

RESULTS

Irrespective of the anatomical location, players with CMSI with severe aponeurotic disruption (AD) took longer to RTP than players with CMSI with no AD: 31.3 ± 12.6 days vs 19.4 ± 10.8 days (mean ± SD; P = .003). A running-related mechanism of injury was associated with a longer RTP period for CMSI overall (adjusted hazard ratio [AHR], 0.59; P = .02). The presence of AD was associated with a longer RTP period for soleus injuries (AHR, 0.6; P = .025). Early recurrence (ie, ≤2 months of the index injury) was associated with older age (AHR, 1.3; P = .001) and a history of ankle injury (AHR, 3.9; P = .032). Older age (AHR, 1.1; P = .013) and a history of CMSI (AHR, 6.7; P = .002) increased the risk of recurrence within 2 seasons. The index injury MRI findings were not associated with risk of recurrence.

CONCLUSION

A running-related mechanism of injury and the presence of AD on MRI were associated with a longer RTP period. Clinical rather than MRI data best indicate the risk of recurrent CMSI.

Anatomical study of the soleus: Application to improved imaging diagnoses

INTRODUCTION

Strains of the soleus are widely found both in amateur and professional athletes. For their accurate regional diagnoses, understanding the anatomy of the spatial relationship between muscular fibers and tendinous structures is important because their interfaces are susceptible sites to muscle strains. Therefore, this study evaluated the precise architecture of the soleus.

MATERIALS AND METHODS

We evaluated the precise anatomical architecture of the soleus in 87 formaldehyde-fixed soleus muscles. To calculate mean relative physiological cross-sectional area of each muscular fiber compartment, we measured the fiber length, volume, and pennation angle in isolated compartments.

RESULTS

The posterior soleus surface was covered by a broad aponeurotic posterior insertion tendon (PIT), which continued inferiorly to the insertion tendon. The anterior surface had three aponeurotic origin tendons, lateral origin tendon (LOT), medial origin tendon (MOT), and tendinous arch, which were arranged along the soleus margins. The anterior bipennate muscle portion (ABP), surrounded by the three origin structures, terminated as the sagittal insertion tendon (SIT), which continued inferiorly to PIT. The posterior main muscle portion behind LOT and MOT was separated into lateral and medial portions by the SIT. The soleus thus possessed a broad musculotendinous junction. Furthermore, ABP exhibited wide structural diversity in shape and size: in extreme cases, it was duplicated or absent.

CONCLUSION

Systematic anatomical descriptions of the soleus will be useful for accurate regional diagnosis of its strains with magnetic resonance imaging and ultrasonography.

Gastrocnemius Injuries in Professional Baseball Players: An Epidemiological Study

BACKGROUND

Gastrocnemius injuries are a common lower extremity injury in elite baseball players. There are no current epidemiological studies focused on gastrocnemius injuries in professional baseball players that provide information on the timing, distribution, and characteristics of such injuries.

HYPOTHESIS

Gastrocnemius injury in professional baseball players is a common injury that is influenced by factors such as age, player position, and time of season.

STUDY DESIGN

Descriptive epidemiological study.

METHODS

Based on Major League Baseball's (MLB's) Health and Injury Tracking System (HITS) database, gastrocnemius injuries that caused time out of play for MLB and Minor League Baseball (MiLB) players during the 2011-2016 seasons were identified. Player characteristics, including age, level of play, and position at time of injury, were collected. Injury-specific factors analyzed included date of injury, time of season, days missed, and activity leading to injury.

RESULTS

A total of 402 gastrocnemius injuries (n = 145, MLB; n = 257, MiLB) occurred during the 2011-2016 seasons. MLB players were significantly older at the time of injury (30.1 years, MLB; 23.9 years, MiLB; P < .001). Base running (36.1%) was the most common activity causing the injury, followed by fielding (23.6%), with 50.3% of base-running injuries sustained on the way to first base. In MLB players, gastrocnemius injuries were most common in infielders (48.3%), followed by pitchers (27.6%) and then outfielders (17.9%), while for MiLB players the injuries were more evenly distributed (33.5%, 28.8%, and 30.7%, respectively). The frequency of injuries in MLB players dropped off after the start of the regular season, whereas MiLB players had a consistent injury rate throughout the year.

CONCLUSION

Gastrocnemius injuries are a common cause of lower extremity injury in professional baseball players, resulting in significant time out of play. Base running, particularly to first base, was the most common activity during injury. Outfielders had the fewest injuries; however, they required the longest time to recover. This study provides the first investigation to date with the HITS database to examine the characteristics and distribution of gastrocnemius injuries in professional baseball players, offering insight into risk factors, injury prevention, and recovery expectations.

Calf muscle strain injuries in elite Australian Football players: A descriptive epidemiological evaluation

BACKGROUND

Calf muscle strain injuries (CMSI) show consistent rates of prevalence and re-injury in elite Australian Football players. An epidemiological evaluation is warranted to better understand the clinical presentation and recovery of CMSI.

PURPOSE

First, to describe the epidemiology of CMSI in elite Australian Football players. Second, to determine if recovery following injury is different according to: (a) injury type (index vs re-injury); (b) muscle injured (soleus vs gastrocnemius); and (c) mechanism of injury (running-related activity vs non running-related activity).

STUDY DESIGN

Descriptive epidemiological.

METHODS

Data retrieved from the Soft Tissue injury Registry of the Australian Football League were analyzed. Sixteen clubs submitted data on CMSI from 2014 to 2017. Data included: player characteristics, training and match history at the time of injury, MRI, and the time to reach recovery milestones.

RESULTS

One hundred and eighty-four CMSI were included (149 index injuries; 35 re-injuries). Soleus injuries were most prevalent (84.6%). Soleus injuries took 25.4 ± 16.2 days to return to play, whereas gastrocnemius injuries took 19.1 ± 14.1 days (P = .097). CMSI sustained during running-related activities took approximately 12 days longer to recover than injuries sustained during non running-related activities (P = .001). Compared to index injuries, re-injuries involved older players (P = .03) and significantly more time was taken to run at >90% of maximum speed, return to full training, and return to play (P ≤ .001). Almost all of the observed re-injuries involved soleus (91.4%).

CONCLUSION

Soleus injuries are more prevalent than gastrocnemius injuries in elite Australian Football players. Prognosis appears to be influenced by clinical factors, with CMSI sustained during running-related activities and re-injuries needing more time to recover.

Is It All About the Fascia? A Systematic Review and Meta-analysis of the Prevalence of Extramuscular Connective Tissue Lesions in Muscle Strain Injury

Background:

The fascia has been demonstrated to represent a potential force transmitter intimately connected to the underlying skeletal muscle. Sports-related soft tissue strains may therefore result in damage to both structures.

Purpose:

To elucidate the prevalence of connective tissue lesions in muscle strain injury and their potential impact on return-to-play (RTP) duration.

Study Design:

Systematic review; Level of evidence, 3.

Methods:

Imaging studies describing frequency, location, and extent of soft tissue lesions in lower limb muscle strain injuries were identified by 2 independent investigators. Weighted proportions (random effects) were pooled for the occurrence of (1) myofascial or fascial lesions, (2) myotendinous lesions, and (3) purely muscular lesions. Study quality was evaluated by means of an adapted Downs and Black checklist, which evaluates reporting, risk of bias, and external validity.

Results:

A total of 16 studies (fair to good methodological quality) were identified. Prevalence of strain injury on imaging studies was 32.1% (95% CI, 24.2%-40.4%) for myofascial lesions, 68.4% (95% CI, 59.6%-76.6%) for myotendinous lesions, and 12.7% (95% CI, 3.0%-27.7%) for isolated muscular lesions. Evidence regarding associations between fascial damage and RTP duration was mixed.

Conclusion:

Lesions of the collagenous connective tissue, namely the fascia and the tendinous junction, are highly prevalent in athletic muscle strain injuries. However, at present, their impact on RTP duration is unclear and requires further investigation.

Effects of the Functional Heel Drop Exercise on the Muscle Architecture of the Gastrocnemius

CONTEXT

The architectural characteristics of a muscle determine its function.

OBJECTIVE

To determine the architectural adaptations of the lateral gastrocnemius (LG) and medial gastrocnemius (MG) muscles after a functional eccentric strength training protocol consisting of heel drop exercises, followed by a subsequent detraining period.

DESIGN

Pretest and posttest.

SETTING

Training rooms and laboratory.

PARTICIPANTS

The participants (N = 45) who were randomly divided into an experimental group (EG, n = 25) and a control group (CG, n = 20).

INTERVENTIONS

The 13-week intervention included participants (N = 45) who were randomly divided into an EG (n = 25) and a CG (n = 20). The EG performed a week of control and training, 8 weeks of eccentric training, and 4 weeks of detraining. The CG did not perform any type of muscular training. The architectural characteristics of the LG and MG muscles were evaluated at rest in both groups using 2-D ultrasound before (pretest-week 1) and after (posttest-week 9) the training, and at the end of the detraining period (retest-week 13).

MAIN OUTCOME MEASURES

One-way repeated measures analysis of variance was used to determine training-induced changes in each of the variables of the muscle architecture.

RESULTS

After the training period, the members of the EG experienced a significant increase in the fascicle length of LG (t = -9.85, d = 2.78, P < .001) and MG (t = -8.98, d = 2.54, P < .001), muscle thickness (t = -6.71, d = 2.86, P < .001) and (t = -7.85, d = 2.22, P < .001), and the pennation angle (t = -10.21, d = 1.88, P < .05) and (t = -1.87, d = 0.53, P < .05), respectively. After the detraining period, fascicle length, muscle thickness, and pennation angle showed a significant decrease. In the CG, no significant changes were observed in any of the variables.

CONCLUSIONS

The heel drop exercise seems to generate adaptations in the architectural conditions of LG and MG, which are also reversible after a detraining period. These results may have practical implications for injury prevention and rehabilitation programs.

A Systematic Review of the Orthopaedic Literature Involving National Football League Players

Background

Orthopaedic injuries of National Football League (NFL) players can have a deleterious effect on their health, with minimal to no high-level evidence on the management of these injuries.

Purpose

To summarize all data published between January 1980 and March 2018 on orthopaedic injuries experienced by NFL candidates and professional players in the NFL.

Study Design

Systematic review; Level of evidence, 4.

Methods

A literature search of studies examining orthopaedic injuries in the NFL was performed through the PubMed, Embase, and CINAHL databases. The review included studies of orthopaedic injuries in college football recruits attending the NFL Combine as well as professional NFL players. Excluded were studies of nonorthopaedic injuries, such as concussions, traumatic brain injury, facial injuries, and vascular injuries, as well as case reports.

Results

A total of 147 articles met the inclusion criteria and were divided into 11 topics based on anatomic site: general (16%), spine (13%), shoulder (13%), elbow (3%), hand and wrist (3%), trunk (0.7%), hip and pelvis (7%), thigh (3%), knee (24%), ankle (5%), and foot (12%). Of these studies, 74% were of level 4 evidence. Most studies obtained data from the NFL Combine database (26%), by searching the internet (24%), and via the NFL Injury Surveillance System (22%). Studies using internet search methods to identify injuries consistently found fewer participants than studies using the NFL Injury Surveillance System.

Conclusion

This systematic review provides National Collegiate Athletic Association and NFL team physicians with a single source of the most current literature regarding orthopaedic injuries in NFL players. Most research was published on knee, spine, shoulder, and foot injuries and consisted of level 4 evidence. A substantial portion of the published literature was based on data obtained from internet searches and may not accurately represent the NFL population.