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CLINICAL REPORT Anterior Cruciate Ligament Injuries: Diagnosis, Treatment, and Prevention abstract The number of anterior cruciate ligament (ACL) injuries reported in athletes younger than 18 years has increased over the past 2 decades. Reasons for the increasing ACL injury rate include the growing number of children and adolescents participating in organized sports, inten- sive sports training at an earlier age, and greater rate of diagnosis because of increased awareness and greater use of advanced medical imaging. ACL injury rates are low in young children and increase sharply during puberty, especially for girls, who have higher rates of noncontact ACL injuries than boys do in similar sports. Intrinsic risk factors for ACL injury include higher BMI, subtalar joint overpronation, generalized ligamentous laxity, and decreased neuromuscular control of knee motion. ACL injuries often require surgery and/or many months of rehabilitation and substantial time lost from school and sports par- ticipation. Unfortunately, regardless of treatment, athletes with ACL injuries are up to 10 times more likely to develop degenerative arthritis of the knee. Safe and effective surgical techniques for children and ado- lescents continue to evolve. Neuromuscular training can reduce risk of ACL injury in adolescent girls. This report outlines the current state of knowledge on epidemiology, diagnosis, treatment, and prevention of ACL injuries in children and adolescents. Pediatrics 2014;133:e1437e1450 INTRODUCTION Anterior cruciate ligament (ACL) injuries are a serious concern for physically active children and adolescents. The ACL is 1 of the 4 major ligaments that stabilize the knee joint (Fig 1). Its main function is to prevent the tibia from sliding forward relative to the femur. The ACL also assists with preventing excessive knee extension, knee varus and valgus movements, and tibial rotation. 1,2 An intact ACL protects the menisci from shearing forces that occur during athletic maneuvers, such as landing from a jump, pivoting, or decelerating from a run. Physicians caring for young athletes have noted an increase in the numbers of ACL injuries over the past 2 decades. 3,4 Reasons for the increase in ACL injury rate include the growing number of children and adolescents participating in organized sports, increased partic- ipation in high-demand sports at an earlier age, and a greater rate of diagnosis as a result of increased awareness that ACL injuries can occur in skeletally immature patients and more frequent use of ad- vanced medical imaging. 48 Cynthia R. LaBella, MD, FAAP, William Hennrikus, MD, FAAP, Timothy E. Hewett, PhD, FACSM, COUNCIL ON SPORTS MEDICINE AND FITNESS, and SECTION ON ORTHOPAEDICS KEY WORDS knee injuries, athletes, sports, adolescents ABBREVIATIONS ACLanterior cruciate ligament CIcondence interval This document is copyrighted and is property of the American Academy of Pediatrics and its Board of Directors. All authors have led conict of interest statements with the American Academy of Pediatrics. Any conicts have been resolved through a process approved by the Board of Directors. The American Academy of Pediatrics has neither solicited nor accepted any commercial involvement in the development of the content of this publication. The guidance in this report does not indicate an exclusive course of treatment or serve as a standard of medical care. Variations, taking into account individual circumstances, may be appropriate. All policy statements from the American Academy of Pediatrics automatically expire 5 years after publication unless reafrmed, revised, or retired at or before that time. www.pediatrics.org/cgi/doi/10.1542/peds.2014-0623 doi:10.1542/peds.2014-0623 PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275). Copyright © 2014 by the American Academy of Pediatrics PEDIATRICS Volume 133, Number 5, May 2014 e1437 FROM THE AMERICAN ACADEMY OF PEDIATRICS Guidance for the Clinician in Rendering Pediatric Care by guest on October 13, 2018 www.aappublications.org/news Downloaded from

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    Anterior Cruciate Ligament Injuries: Diagnosis,Treatment, and Prevention

    abstractThe number of anterior cruciate ligament (ACL) injuries reported inathletes younger than 18 years has increased over the past 2 decades.Reasons for the increasing ACL injury rate include the growing numberof children and adolescents participating in organized sports, inten-sive sports training at an earlier age, and greater rate of diagnosisbecause of increased awareness and greater use of advanced medicalimaging. ACL injury rates are low in young children and increasesharply during puberty, especially for girls, who have higher ratesof noncontact ACL injuries than boys do in similar sports. Intrinsic riskfactors for ACL injury include higher BMI, subtalar joint overpronation,generalized ligamentous laxity, and decreased neuromuscular controlof knee motion. ACL injuries often require surgery and/or many monthsof rehabilitation and substantial time lost from school and sports par-ticipation. Unfortunately, regardless of treatment, athletes with ACLinjuries are up to 10 times more likely to develop degenerative arthritisof the knee. Safe and effective surgical techniques for children and ado-lescents continue to evolve. Neuromuscular training can reduce risk ofACL injury in adolescent girls. This report outlines the current state ofknowledge on epidemiology, diagnosis, treatment, and prevention of ACLinjuries in children and adolescents. Pediatrics 2014;133:e1437e1450


    Anterior cruciate ligament (ACL) injuries are a serious concern forphysically active children and adolescents. The ACL is 1 of the 4 majorligaments that stabilize the knee joint (Fig 1). Its main function is toprevent the tibia from sliding forward relative to the femur. The ACLalso assists with preventing excessive knee extension, knee varus andvalgus movements, and tibial rotation.1,2 An intact ACL protects themenisci from shearing forces that occur during athletic maneuvers,such as landing from a jump, pivoting, or decelerating from a run.

    Physicians caring for young athletes have noted an increase in thenumbers of ACL injuries over the past 2 decades.3,4 Reasons for theincrease in ACL injury rate include the growing number of childrenand adolescents participating in organized sports, increased partic-ipation in high-demand sports at an earlier age, and a greater rate ofdiagnosis as a result of increased awareness that ACL injuries canoccur in skeletally immature patients and more frequent use of ad-vanced medical imaging.48


    KEY WORDSknee injuries, athletes, sports, adolescents

    ABBREVIATIONSACLanterior cruciate ligamentCIconfidence interval

    This document is copyrighted and is property of the AmericanAcademy of Pediatrics and its Board of Directors. All authorshave filed conflict of interest statements with the AmericanAcademy of Pediatrics. Any conflicts have been resolved througha process approved by the Board of Directors. The AmericanAcademy of Pediatrics has neither solicited nor accepted anycommercial involvement in the development of the content ofthis publication.

    The guidance in this report does not indicate an exclusivecourse of treatment or serve as a standard of medical care.Variations, taking into account individual circumstances, may beappropriate.

    All policy statements from the American Academy of Pediatricsautomatically expire 5 years after publication unless reaffirmed,revised, or retired at or before that time.



    PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).

    Copyright 2014 by the American Academy of Pediatrics

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    The incidence of ACL injuries in thegeneral population can be estimatedfrom national registries, which wereestablished in Norway (2004), Denmark(2005), and Sweden (2006) to monitorthe outcomes of ACL reconstructionsurgery. Between 2006 and 2009, allNorwegian hospitals participated in theregistry, with a total compliance of 97%.In the 10- to 19-year age group, theannual incidence of primary ACLreconstructions was 76 per 100 000girls and 47 per 100 000 boys.9 Thisnumber underestimates the true in-cidence of ACL injuries, however, be-cause it does not include those treatednonoperatively.

    Most ACL injuries are sports-related;therefore, injury rates are higher inathletes. The National Collegiate AthleticAssociation Injury Surveillance Systemhas compiled data for 16 sports (8mens and 8 womens) over 16 yearsfrom a sample of colleges and univer-sities (approximately 15%).2 ACL injuryrates were highest in mens springfootball and womens gymnastics (33

    per 100 000 athlete-exposures) (Fig 2).In womens sports, ACL injury ratesrepresented a larger proportion oftotal injuries than in mens sports(3.1% vs 1.9%), with womens basket-ball and womens gymnastics toppingthe list at 4.9% of total injuries.10

    Overall, high school athletes have lowerrates of ACL injuries than do collegiateathletes (5.5 vs 15 per 100 000 athlete-exposures) but a similar injury distri-bution across sports.2,11 Since 2005,the National High School Sports-Related Injury Surveillance Study hascompiled data on the incidence of ACLinjuries in 18 sports.11 From 2007 to2012, ACL injury rates were highest ingirls soccer and boys football (11.7and 11.4 per 100 000 athlete-exposures,respectively) (Fig 3).

    No well-designed epidemiologic studiesto document ACL injury rates have beenconducted in children younger than 14years. Although there have been reportsof sport-related ACL injuries in childrenas young as 5 years, the limited dataavailable suggest that ACL disruptions inchildren younger than 12 years arerare.1216 McCarroll et al16 found that ofthe 1722 ACL injuries diagnosed over

    a 6-year period at their sports medicinecenter, 57 (3%) were in children 14years and younger. The Norwegian ACLSurgical Registry collects data for allACL surgeries performed at participat-ing institutions nationwide. From 2004to 2011, this registry recorded a total ofonly 8 to 9 ACL surgeries each year forchildren 11 to 13 years of age. Thisrepresents a small fraction (0.6%) of thetotal number of ACL surgeries recordedeach year (1441) in this registry acrossall age groups. For the children whohad surgery, the age at the time of in-jury ranged from 9 to 13 years.

    The ACL surgery rate for 12- to 13-year-olds (3.5 per 100 000 citizens) wassubstantially lower than that for 16- to39-year-olds (85 surgeries per 100 000citizens), the age group at highest risk.9

    Again, these numbers underestimatethe actual injury rates, because they donot account for those treated non-operatively.

    Gender Differences

    ACL injury risk begins to increase sig-nificantly at 12 to 13 years of age in girlsand at 14 to 15 years of age in boys.9,12

    Female athletes between 15 and 20

    FIGURE 1Anatomic structures of the knee. LCL, lateralcollateral ligament; MCL, medial collateral ligament;PCL, posterior cruciate ligament. (Reproducedwith permission from Harris SS, Anderson SJ,eds. Care of the Young Athlete. 2nd ed. Elk GroveVillage, IL: American Academy of Pediatrics andAmerican Academy of Orthopedic Surgeons;2009:410.)

    FIGURE 2Collegiate ACL injury rates per 1000 athlete-exposures by sport. (Reproduced with permission fromRenstrom P, Ljungqvist A, Aremdt E, et al. Non-contact ACL injuries in female athletes: an internationalOlympic committee current concepts statement. Br J Sports Med. 2008;42(6):395.10)

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  • years of age account for the largestnumbers of ACL injuries reported(Fig 4). The gender disparity in ACL in-jury rates among athletes begins toappear around the time of the growthspurt (1214 years of age for girls and1416 years of age for boys), peaksduring adolescence, then declines inearly adulthood.10,12 At the high schoollevel, ACL injury rates in gender-comparable sports (soccer, basketball,baseball/softball, track, volleyball) are

    2.5 to 6.2 times higher in girls comparedwith boys.10,11,17 In college athletics,ACL injury rates are 2.4 to 4.1 timeshigher for women, and at the pro-fessional level, ACL injury rates for menand women are essentially equal.4,10,18

    In high school sports, ACL injuriesrepresent a higher proportion of allinjuries in female versus male athletes(4.6% vs 2.5%), with girls basketballtopping the list (6%), followed by girlssoccer, girls gymnastics, and girls

    volleyball (each 5%). Compared withboys, girls are more likely to havesurgery and less likely to return tosports after an ACL injury.17,19 Amongfemale high school basketball players,knee injuries were the most commoncause of permanent disability, ac-counting for up to 91% of season-ending injuries and 94% of injuriesrequiring surgery.20,21


    An ACL injury at an early age is a life-changing event. In addition to surgeryand many months of rehabilitation, thetreatment costs can be substantial($17 000$25 000 per injury), and thetime lost from school and sports par-ticipation can have considerable effectson the athletes mental health and ac-ademic performance.22,23 Although ACLinjuries account for approximately 3%of all injuries in college sports, theyaccount for 88% of injuries associatedwith 10 or more days of time lost fromsports participation. Freedman et al24

    examined the academic transcripts ofcollege students who underwent ACLreconstruction surgery. Compared withan age-matched control group, thosewho had surgery had a significant dropin grade point average of 0.3 pointsduring the semester of injury (P = .04).Similarly, Trentacosta et al25 found thatathletes 18 years and younger who hadACL reconstruction surgery during theschool year reported that it had a neg-ative effect on their grades.

    Beyond these more immediate effects,an ACL injury also has long-term healthconsequences. Regardless of the typeof treatment, athletes with ACL injuryare up to 10 times more likely to de-velop early-onset degenerative kneeosteoarthritis, a condition that not onlylimits ones ability to participate insports but also often leads to chronicpain and disability.26,27 A systematicreview of a series of long-term studiessuggests the rates of degenerative

    FIGURE 3High School ACL injury rates per 100 000 athlete exposures (AEs) by sport. (Data from the NationalHigh School Sports-Related Injury Surveillance Study, 200708 to 201112 school years. Reproducedwith permission from Comstock R, Collins C, McIlvain N. National High-School Sports-Related InjurySurveillance Study, 20092010 School Year Summary. Columbus, OH: The Research Institute at Na-tionwide Childrens Hospital; 2010. Available at: http://www.nationwidechildrens.org/cirp-rio-study-reports.11)

    FIGURE 4Distribution of patients in the Norwegian National Knee Ligament Registry by age and gender.a

    (Reproduced with permission from Renstrom P, Ljungqvist A, Aremdt E, et al. Non-contact ACLinjuries in female athletes: an international Olympic committee current concepts statement. Br JSports Med. 2008;42(6):395.10) aNumber of cases (y-axis) indicates number of ACL reconstructions.

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  • knee osteoarthritis 10 to 20 years af-ter ACL injury are more than 50%.27

    This means children and teenagerswho suffer ACL injuries are likely toface chronic pain and functional limi-tations from knee osteoarthritis intheir 20s and 30s. None of thesestudies, however, demonstrated thatACL reconstruction lowered the riskfor osteoarthritis. In fact, one 5-yearprospective study showed that patientswho had ACL reconstruction had ahigher level of knee arthrosis on radio-graphs and bone scans, compared withpatients who did not undergo ACL re-construction.28


    The mechanism of ACL injuries inathletes is likely multifactorial. Pro-posed theories to explain the mecha-nisms underlying ACL injury includeextrinsic (physical and visual pertur-bations, bracing, and shoe-surfaceinteraction) and intrinsic (anatomic,hormonal, neuromuscular, and bio-mechanical) variables. Identification ofextrinsic and intrinsic risk factorsassociated with the ACL injury mech-anism provides direction for targetedinterventions to high-risk individuals.

    At least 70% of ACL injuries are non-contact in nature29,30; however, thespecific definition of a noncontact ACLinjury varies from study to study. Somedefine a noncontact ACL injury as onethat occurs in the absence of a player-to-player (body-to-body) contact. Othersdefine noncontact ACL injury as onethat occurs in the absence of a directblow to the knee. An ACL injury result-ing from body-to-body contact but withno direct blow to the knee may beclassified as noncontact ACL injurywith perturbation.

    Video analysis of ACL injury duringcompetitive sports play indicatesa common body position associatedwith noncontact ACL injury (Fig 5) inwhich (1) the hip is internally rotated,

    (2) the knee is close to full extension,(3) the foot is planted, and (4) thebody is decelerating, leading to ap-parent valgus collapse of the knee ordynamic knee valgus.3133 ACL injuryis also observed to occur when thebodys center of mass is behind andaway from the base of support or thearea of foot-to-ground contact.31


    ACL injury risk in young athletes islikely multifactorial. Injury data frommany fields demonstrate that numerousphysical and psychological parametersaffect ACL injury rates.


    Genetic factors likely play a role, al-though the genetic underpinnings ofincreased ACL injury risk have onlyrecently begun to be examined.34


    Hormonal factors also likely play a role;however, results of studies investigat-ing hormonal factors are both equivo-cal and controversial.35 Although thefemale knee appears to get slightlymore lax, on the order of 0.5 mm, atmidmenstrual cycle, injuries tend tocluster near the start of menses at thepolar opposite time in the cycle.36,37

    Previous Injury

    Similar to other musculoskeletalinjuries, one of the single best pre-dictors of future ACL injury is previousACL injury. One study found the in-cidence rate of ACL injury in athleteswho have had ACL reconstruction was15 times greater than that of controlsubjects.38 Female athletes were 4times more likely to suffer a secondACL injury in either knee and 6 times

    FIGURE 5Dynamic knee valgus: hips are internally rotated and adducted, tibiae are externally rotated, and feetare everted.

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  • more likely to suffer a new ACL injuryin the contralateral knee than maleathletes. In fact, subsequent injuriesto the contralateral ACL are twice ascommon as reinjury of the recon-structed ACL (11.8% vs 5.8%).39 Ge-netic, anatomic, and neuromuscularfactors likely play a role.

    Age and Gender

    Although ACL injury rates increase withage in both genders, girls have higherrates immediately after the growthspurt.912,16 It is likely that the increa-ses in body weight, height, and bonelength during pubertal developmentunderlie the mechanism of increasedrisk of ACL injury with increasing age.During puberty, the tibia and femurgrow at a rapid rate.40 This growth ofthe 2 longest levers in the human bodytranslates into greater torques on theknee.41 Increasing height leads toa higher center of mass, making mus-cular control of this center of massmore challenging. Increasing bodyweight is associated with greater jointforce that is more difficult to balanceand dampen during high-velocity ath-letic movements. In pubertal boys, tes-tosterone mediates significant increasesin muscular power, strength, and co-ordination, which affords them withgreater neuromuscular control of theselarger body dimensions. Pubertal girlsdo not experience this same growthspurt in muscular power, strength, andcoordination, which likely explains theirhigher rates of ACL injuries comparedwith pubertal boys.41 That preado-lescent athletes show no gender dif-ferences in ACL injury rates furthersupports this theory.12

    Anatomic/Anthropometric Factors

    Greater weight and BMI have beenassociated with increased risk of ACLinjury.31,42 A study of military recruitsfound that body weight or BMI >1 SDabove the mean was associated with

    a 3.2 and 3.5 times greater risk of ACLinjury, respectively.42 In a study of fe-male soccer players older than 8years, BMI was a significant risk fac-tor for knee injury.31

    An increased quadriceps angle (Q an-gle) has been postulated as a riskfactor, but there have been no pro-spective clinical studies to investigatethe relationship between Q angle andACL injury risk.4345 A narrow inter-condylar notch, where the ACL ishoused, is proposed to increase ACLinjury risk, because a narrow notchtends to be associated with a smaller,weaker ACL and also could cause in-creased elongation of the ACL underhigh tension.46,47 Some studies haveshown that a narrow notch increasesrisk of ACL injury42,47,48; however, oth-ers have shown no association be-tween notch width and ACL injury.18,49,50

    Subtalar joint overpronation has beenassociated with noncontact ACL inju-ries,51 likely because overpronationincreases anterior translation of thetibia with respect to the femur, therebyincreasing the strain on the ACL.52

    Generalized joint laxity and knee hy-perextension were found to signifi-cantly increase the risk for ACL injuryin female soccer players.53 Patientswith ACL injury have significantlymore knee recurvatum at 10 and 90degrees of hip flexion and an in-creased ability to touch palms tofloor.29 Athletes with generalized jointlaxity had a 2.7 times greater risk ofACL injury than did those withoutgeneralized laxity, and those with in-creased anterior-posterior laxity ofthe knee, as measured by a kneearthrometer, had an approximately 3times greater risk of ACL injury thandid those without such laxity.42 Jointlaxity affects not only sagittal kneemotion (hyperextension) but alsocoronal knee motion (valgus), whichcan strain the ACL and be related toincreased risk in athletes.29,42,54

    Neuromuscular Factors

    Muscle strength and coordination havea direct effect on themechanical loadingof the ACL during sport movements.55,56

    Poor neuromuscular control of the hipand knee and postural stability deficitshave been shown to be risk factors forACL injury.54,57 Landing and pivotingsports involve a great deal of rapiddeceleration and acceleration move-ments that push and pull the tibia an-teriorly and place the ACL under stress.This tibial translation can be modulatedby hamstrings and quadriceps activ-ity.58,59 In vivo studies show when sub-jects were asked to contract theirmuscles, knee laxity is reduced by 50%to 75%.58 Activation of the quadricepsbefore the hamstrings, a pattern morefrequently seen in female individuals,increases the anterior shear force thatdirectly loads the ACL and also could berelated to increased dynamic valgusalignment at initial contact during cut-ting and landing maneuvers.41,6065 Al-though fatigue is often cited as apotential risk factor for ACL injury, thereare relatively few published studies tosupport or refute this.66



    The patient with an acute ACL teartypically presents with pain, a knee ef-fusion, a reduction in knee motion, anddifficulty bearing weight. Often a pop isheard or felt by the athlete at the timeof injury. The prevalence of an ACL tearin a pediatric athlete with a traumaticknee hemarthrosis is about 65%.67 Thepatient with a chronic ACL tear typicallypresents with recurrent effusions andthe sense that the knee gives way oris unstable with attempts at cutting,twisting, or jumping sports.

    Physical Examination

    In a pediatric athlete with an acutetraumatic knee effusion, the Lachmantest, anterior drawer test, and pivot

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  • shift test are clinical examinations thataid in making the diagnosis of an ACLtear.

    The Lachman test is performed withthe patient supine (Fig 6). The injuredknee is flexed to 30 degrees. The ex-aminer places 1 hand behind the tibiawith the examiners thumb on thetibial tubercle and the other hand onthe patients lower thigh. The tibia ispulled anteriorly. Examinations of bothknees are compared. Increased ante-rior movement of the tibia relative tothe femur without a firm end pointcompared with the examination of theuninjured knee suggests a torn ACL.

    The anterior drawer test also is per-formed with the patient supine butwith the knee flexed to 90 degrees(Fig 7). The examiner grasps the tibiajust below the knee joint, with theexaminers thumbs placed on eitherside of the patellar tendon. The tibia ispulled forward. An increased amountof anterior tibial translation com-pared with the opposite leg or a lackof a firm end point suggests a tornACL.69 Both the Lachman and anteriordrawer tests require a relaxed patientwithout hamstring guarding.

    The pivot shift test is performed withthe patient supine and the knee ex-tended (Fig 8). The examiner stresses

    the lateral side of the knee whilegradually flexing the patients knee. Aclunk sensation occurs when thepartly subluxated tibia relocates inrelation to the femur, indicating thatthe ACL is torn. The pivot shift test isoften difficult to perform in the pedi-atric athlete with an acute knee injurybecause of pain and guarding.

    The Lachman test is considered themost accurate of the 3 commonlyperformed clinical tests for an acuteACL tear, showing a pooled sensitivityof 85% (95% confidence interval [CI]8387) and a pooled specificity of94% (95% CI 9295). The pivot shifttest is very specific, namely 98% (95%CI 9699), but has a poor sensitivity of24% (95% CI 2127).68,69 Last, the kneearthrometer is an objective, accurate,and validated tool that measures, inmillimeters, the amount of tibialtranslation relative to the femur whileperforming a Lachman test and, thus,augments the clinical examinationwhen examining a patient with an ACLtear.70,71


    For the pediatric athlete who presentswith a traumatic knee effusion, plainradiographs should be obtained to ruleout fracture, dislocation, osteochondral

    injury, or physeal injury in addition to,or instead of, an ACL tear. MRI is usuallynot necessary to make the diagnosis ofan ACL tear, as a positive Lachman testresult is sufficient. However, in thepediatric patient whose physical ex-amination is difficult to perform be-cause of pain, swelling, and/or lack ofcooperation or if there is concern forassociated injuries or subtle physealfracture, MRI may be a valuable ancil-lary tool.7276 MRI also can be useful forsurgical planning. Sensitivity andspecificity of MRI for detecting ACLtears in children has been reported tobe 95% and 88%, respectively.76 Formeniscal tears in children, MRI hasbeen reported to be 100% sensitiveand 89% specific.72 One study foundthat the sensitivity, specificity, positivepredictive value, and accuracy of MRIfor identifying all categories of patho-logic changes were lower for pediatric(ages 414 years) versus adolescent(ages 1517 years) patients.75


    The treatment of ACL tears in the pe-diatric athlete is challenging and con-troversial. An ACL tear in a child is nota surgical emergency. Multiple timelydiscussions with the parents and thechild about the appropriate manage-ment options and understanding theirgoals and expectations are very im-portant.73 Surgery is not absolute. Thegeneral indications for surgery includethe patients inability to participate inhis or her chosen sport, instability thataffects activities of daily living, and anassociated repairable meniscal tear or aknee injury with multiple torn ligaments.

    Treatment of ACL injuries in the skele-tally immature patient remains con-troversial, because standard ACLreconstructions involve the use of drillholes that cross the open physes andmay potentially cause growth distur-bance, such as shortening or angulationof the childs leg.8 A meta-analysis of 55

    FIGURE 6Lachman test. (Reproduced with permission from Harris SS, Anderson SJ, eds. Care of the YoungAthlete. 2nd ed. Elk Grove Village, IL: American Academy of Pediatrics and American Academy ofOrthopedic Surgeons; 2009:413.)

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  • studies suggested that the risk of leglength difference or angular leg devia-tions was approximately 2% after ACLreconstruction in children and adoles-cents.77 The authors recommendedrandomized controlled trials to clarifythis risk more accurately. Ideally, sur-gical treatment of an ACL tear ina skeletally immature athlete would bepostponed until skeletal maturity, and

    the athlete would not develop meniscaltears during that waiting time. In thepast, delay in surgical treatment wasvery common. Orthopedic surgeonsrecommended nonoperative treatment,including a brace, rehabilitation, andsports restriction for many monthsuntil skeletal maturity occurred andtraditional ACL surgery could be per-formed safely.73,78,79 For some pediatric

    athletes and parents, conservative man-agement still may be a reasonabletreatment option. However, many pe-diatric athletes and their parents areless inclined to agree to restrict theathletes activity. In such cases, an ACLtear in the pediatric athlete treatedconservatively can lead to additional in-stability episodes, meniscal tears, artic-ular cartilage damage, and early-onsetarthritis.8084 Therefore, most recentliterature now supports early surgeryfor pediatric athletes with an ACL-deficient knee and recurrent episodesof instability.82,8587 Overall, ACL surgeryis about 90% successful in restoringknee stability and patient satisfaction.88

    No consensus exists on the best methodto treat an ACL tear in a pediatric athlete.Safe and effective surgical techniquescontinue to evolve.78 However, the cur-rent literature suggests reasonable,evidenced-based management optionsthat minimize the risks of iatrogenicgrowth plate injury.89 For example, ACLsurgery in a pediatric athlete is oftenperformed via a physeal-sparing tech-nique or a transphyseal technique.86,9092

    The physeal-sparing technique avoidsinjury to the growth plate, but it placesthe graft in a nonanatomic position. Anaccurate understanding of the athletesphysical maturity by determining skele-tal age and Tanner stage helps to identifywhich treatment is best for a specificpatient.73,86,87,9298 The most commonmethod of measuring the patients skel-etal age is to compare an anteropos-terior radiograph of the patients lefthand and wrist to an age-specific ra-diograph in the Greulich and Pyle at-las.94 Tanner stage can be determinedby self-assessment, which has beenshown to be valid and reliable.99

    Patients with open physes at Tannerstage III and skeletal age of less than 14in girls and less than 16 in boys can beoffered the option of activity modifi-cation, functional bracing, rehabilita-tion, and careful follow-up. Surgery is

    FIGURE 7Anterior drawer test. (Reproduced with permission from Sarwark JF, ed. Essentials of Musculo-skeletal Care. 4th ed. Rosemont, IL: American Academy of Orthopedic Surgeons; 2010:638.)

    FIGURE 8Pivot shift test. (Reproduced with permission from Sarwark JF, ed. Essentials of MusculoskeletalCare. 4th ed. Rosemont, IL: American Academy of Orthopedic Surgeons; 2010:637.)

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  • indicated in skeletally immature patientswith a torn ACL and an additional re-pairable meniscal injury and in patientswho failed conservative care. In addi-tion, ACL surgery can be elected bypatients unwilling to comply with ac-tivity restrictions and bracing. Parentsand patients who request surgery be-fore maturation of the growth platesshould be counseled about the risk ofangular or longitudinal growth injuryand the possible need for additionalsurgery.16,100103

    Most orthopedic surgeons select asurgical treatment option based onthe patients skeletal and physiologicage. For example, in the high-risk, mostskeletally immature athlete (skeletalage less than 11 in girls and less than13 in boys, and Tanner stage I or II) anextraphyseal procedure using a bandof the iliotibial tendon or a hamstringtendon graft passed over the top of thelateral femoral condyle and througha groove in the anterior tibia is a rea-sonable surgical option.15,103106 Bothof these extraphyseal proceduresavoid the growth plate to prevent therisk of growth disturbance. A thirdoption for the completely immaturepediatric athlete is a more techni-cally demanding all-epiphyseal pro-cedure using hamstring tendon grafts.Some authors have used intraopera-tive 3-dimensional computed tomog-raphy to confirm the precise tunnellocation and minimize risk of physealinjury.89

    In the intermediate-risk mid-age child(skeletal age 11 to 14 in girls and 13 to16 in boys, and Tanner stage III or IV), theprevious physeal-sparing methods maybe selected; however, many of theseintermediate-maturity patients are safelyand more appropriately treated withtransphyseal reconstruction using small7- to 8-mm centrally placed drill holesand a soft tissue graft, such as thehamstring tendons or an allograft.106109

    Physeal injury can be minimized by us-

    ing a small drill hole and soft tissuegrafts and by placing the fixation awayfrom the physis. Patients and parentsshould be counseled that there remainsa small risk of physeal injury and apossibility of additional surgery forangular or growth disturbance.

    Last, adolescents who are approachingskeletal maturity (skeletal age olderthan 14 in girls and older than 16 in boys,Tanner stage V) can undergo anatomicACL surgery with tibial and femoral drillholes and the surgeons graft of choicewith minimal risk of physeal injury.82,110,111

    Autografts and allografts are bothreasonable graft choices dependingon the patient and surgeon prefer-ences. Autografts have a lower graftfailure rate in 2 studies.112,113

    Rehabilitation after ACL surgery mayneed to be modified for the individualpatient and the particular surgicalprocedure. In general, a graduated re-habilitation program emphasizing fullextension; immediate weight bearing;active range of motion; and strength-ening of the quadriceps, hamstrings, hip,and core can be started in the first fewweeks after surgery. Progressive re-habilitation during the first 3 monthsafter surgery includes range-of-motionexercises, patellar mobilization, pro-prioceptive exercises, endurance train-ing, and closed-chain strengtheningexercises. Straight-line jogging, plyo-metric exercises, and sport-specificexercises are added after 4 to 6months. Return to play typically occurs 7to 9 months after surgery.

    Return to Sport

    Studies of competitive athletes, mostof whom were older than 18 years, ina variety of sports have demonstratedthat 78% to 91% returned to sportsparticipation after ACL reconstruc-tion.114 However, only 44% to 62%returned to their previous level ofathletic performance.114119 Femaleathletes were less likely than male

    athletes to return to sports after ACLinjury or ACL reconstruction.19,119,120



    It is unlikely that prophylactic bracingcan decrease the risk of ACL injury. Therelative effects of 6 different bracedesigns on anterior tibial translationand neuromuscular function were stud-ied in chronically unstable ACL-deficientpatients.121 Bracing decreased ante-rior tibial translation in the range of30% to 40% without the stabilizingcontractions of the hamstrings, quad-riceps, or gastrocnemius muscles. Withmuscle activation and bracing, anteriortibial translation was decreased be-tween 70% and 85%. However, thebraces slowed hamstring muscle re-action times. A brace with a 5-degreeextension stop decreased extensionon landing.122

    Functional bracing after ACL re-construction has been studied usingrandomized controlled cohorts placedinto braced or nonbraced groups.123 Thebraced group was instructed to weara functional knee brace for all cutting,pivoting, or jumping activities for thefirst year after ACL reconstruction.There were no differences betweengroups in knee stability, functionaltesting, subjective knee scores, andrange of motion or strength testing,and the investigators concluded thatpostoperative bracing did not changeoutcomes. Data are insufficient at thistime to determine whether functionalbracing decreases the risk of ACL injuryor reinjury. Knee bracing does not im-prove functional performance of sub-jects after ACL reconstruction and mayactually reduce running and turningspeed.124

    Neuromuscular Training Programs

    Although ACL injuries occur too quick-ly for reflexive muscular activation,

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  • athletes can adopt or preprogramsafer movement patterns that reduceinjury risk during landing, pivoting, orunexpected loads or perturbationsduring sports movements.54,60 Withsufficient neuromuscular control ofknee position to avoid dynamic valgus,knee stability may be improved duringcompetitive sport and the risk of ACLinjury can be significantly reduced. Acollection of prospective cohort studiesand randomized controlled trials haveexamined the effect of neuromusculartraining programs on ACL, knee, andother lower-extremity injuries in soc-cer, basketball, volleyball, and handball(Fig 9).22,125137 Some studies used only1 or 2 types of exercises, such asplyometric exercises and/or balanceexercises, and others applied a morecomprehensive approach by includingplyometrics (repetitive jumping exer-cises designed to build lower-extremitystrength and power), strengthening,stretching, and balance training.

    Systematic examination of the dataextracted from these studies leads toa few potentially valuable general-izations.138140 Plyometric training com-bined with technique training andfeedback to athletes regarding properform were the common components ofprograms that effectively reduced ACLinjury rates. Balance training alone maynot be sufficient to reduce ACL injuryrisk. Although some of the effectiveprograms did not include strengthtraining, those that did were among themost effective at decreasing ACL injuryrates. ACL injury reduction was greatestfor soccer athletes, and combined pre-and in-season training was more ef-fective than pre- or in-season trainingalone. With respect to age, the greatestreduction in injury risk was demon-strated for female athletes in their mid-teens (1418 years) compared withthose in their late teens (1820 years)and adults (>20 years), with 72% riskreduction for those

  • the pediatric athlete whose phys-ical examination is difficult to per-form because of pain, swelling,and lack of cooperation.

    8. An ACL tear in a youth athlete isnot a surgical emergency. Multiplediscussions with the athlete and par-ents may be needed to understandthe athletes goals and parental ex-pectations and to educate the fam-ily about possible treatment options.

    9. The patients skeletal age, measuredby an anteroposterior radiograph ofthe left hand and wrist, and Tannerstage are helpful for the physicianin deciding the most appropriatetreatment of an ACL tear in a skele-tally immature athlete.

    10. Pediatricians and orthopedic sur-geons treating young people withACL injuries should advise themthat regardless of treatment choice,they are at increased risk of early-onset osteoarthritis in the injuredknee. Such discussions should beappropriately documented in thepatients medical record.

    11. Musculoskeletal changes that de-crease dynamic joint stability inhigh-risk female athletes and po-tentially lead to higher injury ratesin this population could be modifiedif neuromuscular training interven-tions are instituted in early-middleadolescence, when the neuromus-cular risk factors for ACL injurystart to develop.

    12. Neuromuscular training appears toreduce the risk of injury in adoles-

    cent female athletes by 72%. Pre-vention training that incorporatesplyometric and strengthening exer-cises, combined with feedback toathletes on proper technique, ap-pears to be most effective.

    13. Pediatricians and orthopedic sur-geons should direct patients athighest risk of ACL injuries (eg, ad-olescent female athletes, patientswith previous ACL injury, general-ized ligamentous laxity, or familyhistory of ACL injury) to appropri-ate resources to reduce their injuryrisk (http://www.aap.org/cosmf).Such discussions also should beappropriately documented in thepatients medical record.

    14. Pediatricians and orthopedic sur-geons who work with schools andsports organizations are encour-aged to educate athletes, parents,coaches, and sports administra-tors about the benefits of neuro-muscular training in reducing ACLinjuries and direct them to appro-priate resources (http://www.aap.org/cosmf).

    LEAD AUTHORSCynthia R. LaBella, MD, FAAPWilliam Hennrikus, MD, FAAPTimothy E. Hewett, PhD, FACSM

    COUNCIL ON SPORTS MEDICINE ANDFITNESS EXECUTIVE COMMITTEE,20122013Joel S. Brenner, MD, MPH, FAAP, ChairpersonAlison Brooks, MD, MPH, FAAPRebecca A. Demorest, MD, FAAPMark E. Halstead, MD, FAAP

    Amanda K. Weiss Kelly, MD, FAAPChris G. Koutures, MD, FAAPCynthia R. LaBella, MD, FAAPMichele LaBotz, MD, FAAPKeith J. Loud, MDCM, MSc, FAAPStephanie S. Martin, MD, FAAPKody A. Moffatt, MD, FAAP


    LIAISONSAndrew J. M. Gregory, MD, FAAP AmericanCollege of Sports MedicineLisa K. Kluchurosky, MEd, ATC National AthleticTrainers AssociationJohn F. Philpot, MD, FAAP Canadian PediatricSocietyKevin D. Walter, MD, FAAP National Federationof State High School Associations

    CONSULTANTTimothy Hewett, PhD

    STAFFAnjie Emanuel, MPH

    SECTION ON ORTHOPEDICS EXECUTIVECOMMITTEE, 20122013Richard M. Schwend, MD, FAAP, ChairpersonJ. Eric Gordon, MD, FAAPNorman Y. Otsuka, MD, FAAPEllen M. Raney, MD, FAAPBrian A. Shaw, MDBrian G. Smith, MDLawrence Wells, MD

    PAST SECTION EXECUTIVE COMMITTEEMEMBERWilliam L. Hennrikus, MD, FAAP, Immediate PastChairperson

    STAFFS. Niccole Alexander, MPP


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