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
Cynthia R. LaBella, MD, FAAP, William Hennrikus, MD, FAAP,Timothy E. Hewett, PhD, FACSM, COUNCIL ON SPORTSMEDICINE AND FITNESS, and SECTION ON ORTHOPAEDICS
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
PEDIATRICS Volume 133, Number 5, May 2014 e1437
FROM THE AMERICAN ACADEMY OF PEDIATRICS
Guidance for the Clinician inRendering Pediatric Care
by guest on October 13, 2018www.aappublications.org/newsDownloaded from
EPIDEMIOLOGY OF ACL INJURY
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.
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)
e1438 FROM THE AMERICAN ACADEMY OF PEDIATRICS by guest on October 13, 2018www.aappublications.org/newsDownloaded from
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
CONSEQUENCES OF ACL INJURY
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