Association of Traumatic Knee Injury With Radiographic Evidence of Knee Osteoarthritis in Military Officers.

OBJECTIVE: The association between knee injury and knee osteoarthritis (OA) is understudied relative to its importance, particularly in younger populations. This study was undertaken to examine the association of knee injury with radiographic features of knee OA in military officers, who have a physically demanding profession and high rates of knee injury. METHODS: Participants were recruited in 2015-2017 from an existing program that enrolled 6,452 military officers during 2004-2009. Officers with a history of knee ligament or meniscal injuries (n = 117 via medical record review) were compared to officers with no history of knee injury (n = 143). Bilateral posteroanterior knee radiographs were obtained using a standardized fixed-flexion positioning frame. All images were read for Kellgren/Lawrence (K/L) grade, osteophyte (OST), and joint space narrowing (JSN) scores. Data were analyzed using linear-risk regression models with generalized estimating equations. RESULTS: Injured and noninjured participants were similar (mean age 28 years, mean body mass index 25 kg/m2 , ~40% female). The mean time from first knee injury to imaging among injured participants was 9.2 years. Compared with noninjured knees, greater prevalence of radiographic OA (K/L grade ≥ 2), OST (grade ≥ 1), and JSN (grade ≥ 1) was observed among injured knees, with prevalence differences of +16% (95% confidence interval [95% CI] 10%, 22%), +29% (95% CI 20%, 38%), and + 17% (95% CI 10%, 24%), respectively. Approximately 1 in 6 officers with prior knee injury progressed to radiographic OA by age 30 years. CONCLUSION: At the midpoint of a projected 20-year military career, officers with a history of traumatic knee injury have a markedly increased prevalence of knee radiographic OA compared to officers without injury.

Current Sport Organization Guidelines From the AMSSM 2019 Youth Early Sport Specialization Research Summit.

CONTEXT: Youth athletes may be at elevated risk for adverse health due to sport specialization. Sport organizations have developed guidelines for participation during growth and development. OBJECTIVE: To assess youth sport development guidelines using a 15-item framework across sport organizations and governing bodies in soccer, basketball, ice hockey, and swimming. DATA SOURCES: English-language results from January 1, 2000, to December 31, 2018, from published sport organization guidelines and athlete development plans. STUDY SELECTION: Two investigators independently reviewed publications identified from sport organizations. A total of 23 guidelines were incorporated, including 5 general sport organizations and 18 sport-specific guidelines. STUDY DESIGN: Systematic review. LEVEL OF EVIDENCE: Level 4. DATA EXTRACTION: Two investigators independently identified all recommendations that fit within a predetermined rubric of recommendations encompassing 4 domains: Psychological Development/Approach, Physical Development/Load, Facilities and Resources, and Timing and Monitoring of Specialization. Sport-specific guidelines on volume were summarized. RESULTS: Sport organizations and sport-specific guidelines had consensus on 2 items out of the 15-item: emphasis on early skill development and access to well-trained coaches. While recommended by all sports organization, multisport participation was emphasized by 3 of 4 sports, excluding soccer. Volume recommendations were inconsistent between and within sports. No group proposed methods to monitor athlete well-being. CONCLUSION: This review highlights areas of agreement within sport organizations and governing bodies. Creating a framework to guide youth sport specialization may lead to specific and consistent guidelines.

Systematic Review of Health Organization Guidelines Following the AMSSM 2019 Youth Early Sport Specialization Summit.

CONTEXT: Youth sport specialization may place young athletes at increased risk for negative impacts to their physical and/or psychological health. In response to these health concerns, several health organizations have created guidelines and position statements to guide parents and practitioners toward best practices for management of the young athlete. OBJECTIVE: To systematically review and synthesize current organizations' recommendations and guidelines regarding youth sport specialization. DATA SOURCES: English-language articles from January 1, 2000, to December 31, 2018, in the NCBI Pubmed, Embase, Cochrane, CINAHL, and SPORTDiscus databases. STUDY SELECTION: Articles that reported on recommendations or interventions by health organizations or health representatives of sports organizations. A total of 56 articles were assessed, with 11 meeting inclusion eligibility criteria. STUDY DESIGN: Systematic review. LEVEL OF EVIDENCE: Level 4. DATA EXTRACTION: Two investigators independently identified all recommendations within the results that fit within a 15-item framework encompassing 4 domains: Psychological Development/Approach, Physical Development/Load, Facilities and Resources, and Timing and Monitoring of Specialization. RESULTS: Recommendations across organizations were primarily clustered in the Physical Development/Load (43%), Facilities and Resources (48%), and Sport Specialization (55%) domains. In contrast, the Psychological Development/Approach domain had fewer recommendations (20%). The most common recommendations endorsed concepts: "Monitor athlete well-being," "Youth athletes need access to well-trained, quality coaches," "Multi-sport participation," "Limit early organized participation and/or training," and "Parents require awareness of training, coaching, and best practices." The level of evidence provided to support a given recommendation varied significantly. The level of detail and the consistency of terms used throughout the results were typically low. Recommendations were frequently made without reference to potential outcome measures or specific strategies that could be used for practical implementation in the community. CONCLUSION: There was broad representation of different aspects of specialization but limited consistency between health organization guidelines. Adopting a framework for recommendations as used in this review could assist organizations in structuring future recommendations that are specific, measurable, and framed in a manner that will promote action in the youth sport community.

Clinical Practice Guidelines for Exertional Rhabdomyolysis: A Military Medicine Perspective.

ABSTRACT: Exertional rhabdomyolysis (ER) is an uncommon condition with a paucity of evidence-based guidance for diagnosis, management, and return to duty or play. Recently, a clinical practice guideline for diagnosis and management of ER in warfighters was updated by a team of military and civilian physicians and researchers using current scientific literature and decades of experience within the military population. The revision concentrated on challenging and controversial clinical questions with applicability to providers in the military and those in the greater sports medicine community. Specific topics addressed: 1) diagnostic criteria for ER; 2) clinical decision making for outpatient versus inpatient treatment; 3) optimal strategies for inpatient management; 4) discharge criteria; 5) identification and assessment of warfighters/athletes at risk for recurrent ER; 6) an appropriate rehabilitative plan; and finally, 7) key clinical questions warranting future research.

Defining a Research Agenda for Youth Sport Specialization in the United States: The AMSSM Youth Early Sport Specialization Summit.

ABSTRACT: Sport specialization is becoming increasingly common among youth and adolescent athletes in the United States and many have raised concern about this trend. Although research on sport specialization has grown significantly, numerous pressing questions remain pertaining to short- and long-term effects of specialization on the health and well-being of youth, including the increased risk of overuse injury and burnout. Many current elite athletes did not specialize at an early age. Methodological and study design limitations impact the quality of current literature, and researchers need to prioritize pressing research questions to promote safe and healthy youth sport participation. The American Medical Society for Sports Medicine hosted a Youth Early Sport Specialization Summit in April 2019 with the goal of synthesizing and reviewing current scientific knowledge and developing a research agenda to guide future research in the field based on the identified gaps in knowledge. This statement provides a broad summary of the existing literature, gaps and limitations in current evidence, and identifies key research priorities to help guide researchers conducting research on youth sport specialization. Our goals are to help improve the quality and relevance of research on youth sport specialization and to ultimately assure that opportunities for healthy and safe sport participation continue for all youth.

Defining a research agenda for youth sport specialisation in the USA: the AMSSM Youth Early Sport Specialization Summit.

Sport specialisation is becoming increasingly common among youth and adolescent athletes in the USA and many have raised concern about this trend. Although research on sport specialisation has grown significantly, numerous pressing questions remain pertaining to short-term and long-term effects of specialisation on the health and well-being of youth, including the increased risk of overuse injury and burnout. Many current elite athletes did not specialise at an early age. Methodological and study design limitations impact the quality of current literature, and researchers need to prioritise pressing research questions to promote safe and healthy youth sport participation. The American Medical Society for Sports Medicine hosted a Youth Early Sport Specialization Summit in April 2019 with the goal of synthesising and reviewing current scientific knowledge and developing a research agenda to guide future research in the field based on the identified gaps in knowledge. This statement provides a broad summary of the existing literature, gaps and limitations in current evidence and identifies key research priorities to help guide researchers conducting research on youth sport specialisation. Our goals are to help improve the quality and relevance of research on youth sport specialisation and to ultimately assure that opportunities for healthy and safe sport participation continue for all youth.

Regenerative Injectable Therapies: Current Evidence.

Regenerative medicine is a growing field of musculoskeletal treatments that focuses on amplifying the body's natural healing properties to improve function and pain after injury. Regenerative treatments are applied locally at the site of injury and work though different mechanisms, some of which are unexplained at this time. Current evidence demonstrates benefit for certain regenerative treatments, but further standardization of treatments and additional studies are required to provide additional data to support specific regenerative treatments. This review seeks to explore the evidence and discuss appropriate use of the most common regenerative treatments including platelet-rich plasma, prolotherapy, autologous mesenchymal stem cells, human-derived allograft products, and saline.

Evaluating an Algorithm and Clinical Prediction Rule for Diagnosis of Bone Stress Injuries.

BACKGROUND: A novel algorithm and clinical prediction rule (CPR), with 18 variables, was created in 2014. The CPR generated a bone stress injury (BSI) score, which was used to determine the necessity of imaging in suspected BSI. To date, there are no validated algorithms for imaging selection in patients with suspected BSI. HYPOTHESIS: A simplified CPR will assist clinicians with diagnosis and decision making in patients with suspected BSI. STUDY DESIGN: Prospective cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 778 military trainees with lower extremity pain were enrolled. All trainees were evaluated for 18 clinical variables suggesting BSI. Participants were monitored via electronic medical record review. Then, a prediction model was developed using logistic regression to identify clinical variables with the greatest predictive value and assigned appropriate weight. Test characteristics for various BSI score thresholds were calculated. RESULTS: Of the enrolled trainees, 204 had imaging-confirmed BSI in or distal to the femoral condyles. The optimized CPR selected 4 clinical variables (weighted score): bony tenderness (3), prior history of BSI (2), pes cavus (2), and increased walking/running volume (1). The optimized CPR with a score ≥3 yielded 97.5% sensitivity, 54.2% specificity, and 98.2% negative predictive value. An isolated measure, bony tenderness, demonstrated similar statistical performance. CONCLUSION: The optimized CPR, which uses bony tenderness, prior history of BSI, pes cavus, and increased walking/running volume, is valid for detecting BSI in or distal to the femoral condyles. However, bony tenderness alone provides a simpler criterion with an equally strong negative predictive value for BSI decision making. CLINICAL RELEVANCE: For suspected BSI in or distal to the femoral condyles, imaging can be deferred when there is no bony tenderness. When bony tenderness is present in the setting of 1 or more proven risk factors and no clinical evidence of high-risk bone involvement, presumptive treatment for BSI and serial radiographs may be appropriate.

Impact of youth sports specialisation on career and task-specific athletic performance: a systematic review following the American Medical Society for Sports Medicine (AMSSM) Collaborative Research Network's 2019 Youth Early Sport Specialisation Summit.

OBJECTIVE: The impact, positive or negative, of youth sport specialisation (YSS) on short-term and long-term performance is not fully understood; however, the desire to maximise performance goals is generally considered the primary reason children and adolescents specialise at a young age. We performed a systematic review of original research to establish the association of YSS and task-focused or career-focused performance outcomes. DESIGN: Systematic review. DATA SOURCES: Databases searched include PubMed, EMBASE, Cochrane, CINAHL and SPORTDiscus. ELIGIBILITY CRITERIA: We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to identify peer-reviewed research articles published in English between 1 January 1990 and 31 December 2018 that reported original findings on the association of YSS and performance outcomes. Studies without an explicit measure of sport specialisation, for example, volume measures without measuring sport specialisation, were excluded. RESULTS: Twenty-two articles were included in the final review; 15 addressed career performance outcomes and 7 considered task performance outcomes. All identified studies were cross-sectional or retrospective in design. The proportion of elite athletes who specialised early ranged between 7% and 85%, depending on sport and definition of specialisation. Elite athletes often specialised between the ages of 14 and 15 compared with their non-elite or semi-elite peers who typically specialised prior to 13 years. In addition, neuromuscular control, anterior reach asymmetry and physical task outcomes did not differ by specialisation status. CONCLUSION: The volume and methodological rigour of published research in this field are limited. Our review suggests that YSS is not required to achieve success at elite levels. YSS also does not appear to improve task-related performance (eg, anterior reach, neuromuscular control) outcomes for specialised athletes when compared with non-specialised athletes during childhood and adolescence.

Association of Splenic Rupture and Infectious Mononucleosis: A Retrospective Analysis and Review of Return-to-Play Recommendations.

BACKGROUND: Infectious mononucleosis is typically a self-limited disease commonly affecting young adults. Splenic rupture is a rare but serious complication affecting 0.1% to 0.5% of patients with mononucleosis. Current guidelines (based on published case reports) recommend complete activity restriction for 3 weeks after onset of mononucleosis symptoms to reduce rupture risk. We examined actual timing of mononucleosis-associated splenic injury using a large repository of unpublished patient data. HYPOTHESIS: The risk of splenic injury after infectious mononucleosis will remain elevated longer than previously estimated. STUDY DESIGN: Retrospective case series. LEVEL OF EVIDENCE: Level 4. METHODS: The Military Health System Management Analysis and Reporting Tool (M2) was used to conduct a retrospective chart review. Coding records of TRICARE beneficiaries aged 5 to 65 years between 2006 and 2016 were screened. Patients diagnosed with both splenic injury and mononucleosis-like symptoms were identified, and their medical records were reviewed for laboratory confirmation of infection and radiographically evident splenic injury. RESULTS: A total of 826 records of splenic injury were found in M2. Of these, 42 cases met the study criteria. Mean time to splenic injury was 15.4 (±13.5) days. Only 73.8% (n = 31) of injuries occurred within 21 days, and 90.5% (n = 38) of splenic injuries occurred within 31 days of symptom onset. CONCLUSION: A substantial number of splenic injuries occur between 21 and 31 days after symptom onset. While most splenic injuries were atraumatic, consideration should be given to extending return-to-play guidelines to 31 days after symptom onset to minimize risk. Risk of chronic pain after splenic injury may be higher than previously believed. CLINICAL RELEVANCE: The risk for postmononucleosis splenic injuries remains elevated longer than current guidelines suggest. Restricting activity for 31 days after mononucleosis symptom onset may reduce the risk of splenic injury.

Functional Movement Assessments Are Not Associated with Risk of Injury During Military Basic Training.

INTRODUCTION: Musculoskeletal injuries (MSK-I) in the U.S. military accounted for more than four million medical encounters in 2017. The Military Entrance Processing Screen to Assess Risk of Training (MEPSTART) was created to identify MSK-I risk during the first 180 days of military service. METHODS: Active duty applicants to the United States Army, Navy, Air Force, and Marine Corps between February 2013 and December 2014 who consented completed a behavioral and injury history questionnaire and the MEPSTART screen [Functional Movement Screen (FMS), Y-Balance Test (YBT), Landing Error Scoring System (LESS), and Overhead Squat assessment (OHS)] the day they shipped to basic training. Male (n = 1,433) and Female (n = 281) applicants were enrolled and MSK-I were tracked for 180 days. Binomial logistic regression and multivariate Cox proportional hazards modeling were used to assess relationships among MEPSTART screens and MSK-I independent of age, BMI, sex, Service, injury history, and smoking status. Analyses were finalized and performed in 2017. RESULTS: The only functional screen related to injury was the LESS score. Compared to those with good LESS scores, applicants with poor LESS scores had lower odds of MSK-I (OR = 0.54, 95% CI = 0.30-0.97, p = 0.04), and a lower instantaneous risk of MSK-I during the first 180 d (HR = 0.58, 95%CI = 0.34-0.96, p = 0.04). However, secondary receiver operator characteristic (ROC) analyses revealed poor discriminative value (AUC = 0.49, 95%CI = 0.43-0.54). CONCLUSIONS: Functional performance did not predict future injury risk during the first 180 days of service. Poor LESS scores were associated with lower injury risk, but ROC analyses revealed little predictive value and limited clinical usefulness. Comprehensive risk reduction strategies may be preferable for mitigating MSK-I in military training populations.

A Cluster of Exertional Rhabdomyolysis Cases in a ROTC Program Engaged in an Extreme Exercise Program.

Exertional rhabdomyolysis (ER) is on the rise among service members and high school and college athletes. Reported risk factors for ER include fitness level, sudden increase in exercise intensity and duration, and eccentric predominant exercise. This study examined an ER cluster among Reserve Officer Training Corps cadets who participated in a mandatory, timed, extreme conditioning program (ECP) workout. Forty-four cadets participated in this ECP; 11 were subsequently hospitalized with ER. Thirty-five cadets, including all who developed ER, completed a questionnaire to assess ECP times, prior fitness scores, and other ER risk factors. Cadets completed the ECP workout as individuals or in teams. Nine of 25 (36%) individual and two of 10 (20%) team participants were hospitalized with ER. Among the cadets, no associations were noted between hospitalization for ER and finish time, previous fitness scores, or dietary supplement use. The relative risk of developing ER was significantly increased in those who consumed alcohol in the week preceding the ECP (RR = 4.20; 95% CI 1.95, 9.03). In this cohort of Reserve Officer Training Corps cadets, an ECP resulted in a high rate of hospitalization for ER. Contrary to reported ER risk factors, higher baseline fitness was not protective. Rather, cadet knowledge that ECP performance was strongly linked to final cadet ranking greatly influenced intensity of effort.

Effect of a Lower Extremity Preventive Training Program on Physical Performance Scores in Military Recruits.

Peck, KY, DiStefano, LJ, Marshall, SW, Padua, DA, Beutler, AI, de la Motte, SJ, Frank, BS, Martinez, JC, and Cameron, KL. Effect of a lower extremity preventive training program on physical performance scores in military recruits. J Strength Cond Res 31(11): 3146-3157, 2017-Exercise-based preventive training programs are designed to improve movement patterns associated with lower extremity injury risk; however, the impact of these programs on general physical fitness has not been evaluated. The purpose of this study was to compare fitness scores between participants in a preventive training program and a control group. One thousand sixty-eight freshmen from a U.S. Service Academy were cluster-randomized into either the intervention or control group during 6 weeks of summer training. The intervention group performed a preventive training program, specifically the Dynamic Integrated Movement Enhancement (DIME), which is designed to improve lower extremity movement patterns. The control group performed the Army Preparation Drill (PD), a warm-up designed to prepare soldiers for training. Main outcome measures were the Army Physical Fitness Test (APFT) raw and scaled (for age and sex) scores. Independent t tests were used to assess between-group differences. Multivariable logistic regression models were used to control for the influence of confounding variables. Dynamic Integrated Movement Enhancement group participants completed the APFT 2-mile run 20 seconds faster compared with the PD group (p < 0.001), which corresponded with significantly higher scaled scores (p < 0.001). Army Physical Fitness Test push-up scores were significantly higher in the DIME group (p = 0.041), but there were no significant differences in APFT sit-up scores. The DIME group had significantly higher total APFT scores compared with the PD group (p < 0.001). Similar results were observed in multivariable models after controlling for sex and body mass index (BMI). Committing time to the implementation of a preventive training program does not appear to negatively affect fitness test scores.

The Interrelationship of Common Clinical Movement Screens: Establishing Population-Specific Norms in a Large Cohort of Military Applicants.

CONTEXT: Musculoskeletal injuries (MSK-Is) are a leading cause of missed duty time and morbidity in the military. Modifiable risk factors for MSK-Is, such as inadequate core stability, poor movement patterns, and dynamic balance deficits, have not been identified in military applicants on entering service. OBJECTIVE: To establish normative functional movement data using a series of screens in military applicants entering basic training and explore relationships among several movement tests. DESIGN: Cross-sectional study. SETTING: Military Entrance Processing Station. PATIENTS OR OTHER PARTICIPANTS: A total of 1714 (1434 male, 280 female) military applicants entering the US Army (n = 546), Navy (n = 414), Air Force (n = 229), or Marine Corps (n = 525). INTERVENTION(S): We conducted the Functional Movement Screen (FMS), Y-Balance Test (YBT), overhead squat (OHS), and Landing Error Scoring System (LESS). Movements were assessed using the scoring convention for each screen. MAIN OUTCOME MEASURE(S): The FMS, YBT, OHS, and LESS scores and associations among the movement screens as well as clinical meaningfulness. RESULTS: A total of 1037 of the 1714 enrolled applicants were screened on the day they left for basic training. Normative means for this population were established: FMS = 14.7 ± 1.8, YBT anterior-reach difference = 3.1 ± 3.0 cm, mean YBT composite differences = 8.0 ± 6.8 cm, mean YBT composite percentage = 90.9% ± 8.3%, OHS errors = 5.0 ± 2.8, and LESS score = 5.7 ± 2.1. Backward regression results revealed that the YBT composite percentage was related to the FMS and OHS scores in males and to the FMS and LESS results in females. However, clinically meaningful relationships between the tests varied for both males and females. CONCLUSIONS: Sex-normative values for the FMS, YBT, OHS, and LESS screens were established for US military applicants, and some of the assessments overlapped. Overall, males performed better on the OHS and LESS and achieved a greater YBT composite percentage than females. The regression results revealed movement screen performance relationships that varied by sex and clinical meaningfulness. In future studies, we will determine if performance on any of the screens is associated with MSK-Is in basic trainees.

Preventing Exertional Death in Military Trainees: Recommendations and Treatment Algorithms From a Multidisciplinary Working Group.

Despite aggressive prevention programs and strategies, nontraumatic exertional sudden death events in military training continue to prove a difficult challenge for the Department of Defense. In November 2014, the 559th Medical Group at Joint Base San Antonio-Lackland, Texas, hosted a working group on sudden exertional death in military training. Their objectives were three-fold: (1) determine best practices to prevent sudden exertional death of military trainees, (2) determine best practices to establish safe and ethical training environments for military trainees with sickle cell trait, and (3) develop field-ready algorithms for managing military trainees who collapse during exertion. This article summarizes the major findings and recommendations of the working group.

The Relationship Between Functional Movement, Balance Deficits, and Previous Injury History in Deploying Marine Warfighters.

Screening for primary musculoskeletal injury (MSK-I) is costly and time-consuming. Both the Functional Movement Screen (FMS) and the Y-Balance Test (YBT) have been shown to predict future MSK-I. With a goal of optimizing the efficiency of primary MSK-I screening, we studied associations between performance on the FMS and YBT and whether history of MSK-I influenced FMS and YBT scores. In total, 365 deploying Marines performed the FMS and YBT as prescribed. Composite and individual scores were each categorized as high risk or low risk using published injury thresholds: High-risk FMS included composite scores ≤14 and right-to-left (R/L) asymmetry for Shoulder Mobility, In-Line Lunge, Straight Leg Raise, Hurdle Step, or Rotary Stability. High-risk YBT consisted of anterior, posteromedial, and/or posterolateral R/L differences >4 cm and/or composite differences ≥12 cm. Pearson's χ tests evaluated associations between: (a) all FMS and YBT risk groups and (b) previous MSK-I and all FMS and YBT risk groups. Marines with high-risk FMS were twice as likely to have high-risk YBT posteromedial scores (χ = 10.2, p = 0.001; odds ratio [OR] = 2.1, 95% confidence interval [CI] = 1.3-3.2). History of any MSK-I was not associated with high-risk FMS or high-risk YBT. However, previous lower extremity MSK-I was associated with In-Line Lunge asymmetries (χ = 9.8, p = 0.002, OR = 2.2, 95% CI = 1.3-3.6). Overall, we found limited overlap in FMS and YBT risk. Because both methods seem to assess different risk factors for injury, we recommend FMS and YBT continue to be used together in combination with a thorough injury history until their predictive capacities are further established.

Association of Injury History and Incident Injury in Cadet Basic Military Training.

PURPOSE: This study aimed to determine the association between injury history at enrollment and incident lower extremity (LE) injury during cadet basic training among first-year military cadets. METHODS: Medically treated LE injuries during cadet basic training documented in the Defense Medical Surveillance System were ascertained in a prospective cohort study of three large US military academies from 2005 to 2008. Both acute injuries (International Classification of Disease, Ninth Revision, codes in the 800-900s, including fracture, dislocations, and sprains/strains) and injury-related musculoskeletal injuries (International Classification of Disease, Ninth Revision, codes in the 700s, including inflammation and pain, joint derangement, stress fracture, sprain/strain/rupture, and dislocation) were included. Risk ratio (RR) and 95% confidence interval (CI) were computed using multivariate log-binomial models stratified by gender. RESULTS: During basic training, there were 1438 medically treated acute and 1719 musculoskeletal-related LE injuries in the 9811 cadets. The most frequent LE injuries were sprains/strains (73.6% of acute injuries) and inflammation and pain (89.6% of musculoskeletal-related injuries). The overall risk of incident LE injury was 23.2% (95% CI = 22.3%-24.0%). Cadets with a history of LE injury were at increased risk for incident LE injury. This association was identical in males (RR = 1.74, 95% CI = 1.55-1.94) and females (RR = 1.74, 95% CI = 1.52-1.99). In site-specific analyses, strong associations between injury history and incident injury were observed for hip, knee ligament, stress fracture, and ankle sprain. Injury risk was greater (P < 0.01) for females (39.1%) compared with males (18.0%). The elevated injury risk in females (RR = 2.19, 95% CI = 2.04-2.36) was independent of injury history (adjusted RR = 2.09, 95% CI = 1.95-2.24). CONCLUSION: Injury history upon entry to the military is associated with the incidence of LE injuries sustained during cadet basic training. Prevention programs targeted at modifiable factors in cadets with a history of LE injury should be considered.