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Unique Considerations for the Pediatric Athlete During Rehabilitation and Return to Sport After Anterior Cruciate Ligament Reconstruction

      Abstract

      Anterior cruciate ligament (ACL) injuries and surgical intervention in the pediatric population have increased in the recent years. Although surgical techniques have advanced, evidence-based rehabilitation guidelines that consider all aspects of the youth athlete are currently lacking. The purpose of this commentary is to review the current evidence on unique considerations for the pediatric and adolescent population during rehabilitation and return to sport after ACL reconstruction (ACLR), with a focus on children under 18 years of age. This review revealed that returning a youth athlete to sport after ACLR requires knowledge and appreciation of various aspects of the growing athlete different from adults. In addition to postoperative precautions that contribute to a slow rehabilitation process, young athletes need additional time for strength gains. Address risk of reinjury and for contralateral injury by using neuromuscular training and rigorous return-to-sport training programs. Consider return to sport after 9 months because the reinjury rate is high in this population. A combination of time and objective measures, both quantitative and qualitative criteria, and psychological readiness should be used to assess readiness to return to sport and decrease risk of future injury. Healthcare providers should be aware of the psychosocial impact of injury on the youth athletes and refer to sport psychology when necessary.

      Level of Evidence

      Level V.
      Over the last 2 decades, anterior cruciate ligament (ACL) injuries and surgical intervention in children and adolescents have been increasing.
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      • Michalowitz A.
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      ACL injuries aren’t just for girls: The role of age in predicting pediatric ACL injury.
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      Trends in pediatric ACL reconstruction from the PHIS database.
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      ACL tears in school-aged children and adolescents over 20 years.
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      Trends in pediatric and adolescent anterior cruciate ligament injury and reconstruction.
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      Trends in anterior cruciate ligament reconstruction in the United States.
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      Incidence and trends of anterior cruciate ligament reconstruction in the United States.
      This increase is often attributed to increased participation in competitive organized sports,
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      The risk for a cruciate ligament injury of the knee in adolescents and young adults: A population-based cohort study of 46,500 people with a 9 year follow-up.
      early sports specialization,
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      Injury risk associated with sports specialization and activity volume in youth.
      and year-round training and competition.
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      • Kocher M.S.
      Anterior cruciate ligament injuries in children and adolescents.
      Furthermore, advancements in surgical techniques allow for early reconstruction of the ACL in the skeletally immature patient, restoring knee stability, decreasing risk of subsequent injury to the knee, improving rate of return to play, and providing favorable long-term outcomes.
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      • Dawkins B.J.
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      • et al.
      Early operative versus delayed operative versus nonoperative treatment of pediatric and adolescent anterior cruciate ligament injuries: A systematic review and meta-analysis.
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      • Delos D.
      • et al.
      Reconstruction of the anterior cruciate ligament in the skeletally immature athlete: A review of current concepts AAOS exhibit selection.
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      Outcomes of physeal-sparing ACL reconstruction with iliotibial band autograft in skeletally immature prepubescent children.
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      • Lawrence J.T.R.
      • Marx R.G.
      Early ACL reconstruction in children leads to less meniscal and articular cartilage damage when compared with conservative or delayed treatment.
      Although pediatric athletes return to sports at a high rate after ACL reconstruction (ACLR),
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      • Memon M.
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      • Ayeni O.R.
      Over 90 % of children and adolescents return to sport after anterior cruciate ligament reconstruction: A systematic review and meta-analysis.
      subsequent ACL injuries to the ipsilateral or contralateral leg are reported to be as high as 32%.
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      Return to sport after pediatric anterior cruciate ligament reconstruction and its effect on subsequent anterior cruciate ligament injury.
      ,
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      • Hewett T.E.
      Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport.
      Recent studies of revision ACLR in pediatric and adolescent populations have reported lower functional outcomes, lower return to sport rates, significant risk of contralateral ACL injury, and high rates of revision graft injury
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      Revision ACL reconstruction in children and adolescents.
      ,
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      Outcomes of revision anterior cruciate ligament surgery in adolescents.
      compared to primary ACLR. Revision ACLR has also been associated with more meniscal and cartilage abnormalities,
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      • Tepolt F.A.
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      • Micheli L.J.
      • Kocher M.S.
      Revision ACL reconstruction in children and adolescents.
      • Ouillette R.
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      • Chambers H.
      • Bastrom T.
      • Pennock A.
      Outcomes of revision anterior cruciate ligament surgery in adolescents.
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      Revision ACL reconstruction in adolescent patients.
      which increases concern for long-term knee and general health.
      Youth are undergoing changes both physiologically and psychologically which warrant consideration. As such, protocols and recommendations created for adults cannot merely be extrapolated to children and adolescents with ACL injuries. Physiologically, pediatric athletes have slower strength recovery, decreased neuromuscular control, poor rates of passing return-to-sport (RTS) criteria, and higher reinjury rates than adults, suggesting that RTS testing criteria and timeline to RTS created for adults may not be appropriate. Sports also offers many psychosocial benefits for the youth including socialization, building teamwork and leadership skills, and improving self-esteem.
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      • LaBella C.R.
      • Brooks M.A.
      • et al.
      Sports specialization and intensive training in young athletes.
      Not being able to play has significant impact on the youth athlete physically, mentally, and socially. Therefore healthcare providers must not only ensure full recovery and RTS but also minimize the risk of reinjury. The purpose of this commentary is to review the current evidence on unique considerations for the pediatric and adolescent population during rehabilitation and RTS after ACL reconstruction (ACLR), with a focus on children under 18 years of age.

      ACL Injuries in Children and Adolescents

      The number of ACL injuries have been increasing across all age groups, even in children as young as 5 to 10 years of age.
      • Tepolt F.A.
      • Feldman L.
      • Kocher M.S.
      Trends in pediatric ACL reconstruction from the PHIS database.
      • Beck N.A.
      • Lawrence J.T.R.
      • Nordin J.D.
      • DeFor T.A.
      • Tompkins M.
      ACL tears in school-aged children and adolescents over 20 years.
      • Werner B.C.
      • Yang S.
      • Looney A.M.
      • Gwathmey F.W.
      Trends in pediatric and adolescent anterior cruciate ligament injury and reconstruction.
      ,
      • Dodwell E.R.
      • Lamont L.E.
      • Green D.W.
      • Pan T.J.
      • Marx R.G.
      • Lyman S.
      20 years of pediatric anterior cruciate ligament reconstruction in New York state.
      ,
      • Shea K.G.
      • Pfeiffer R.
      • Jo H.W.
      • Curtin M.
      • Apel P.J.
      Anterior cruciate ligament injury in pediatric and adolescent soccer players: An analysis of insurance data.
      In children younger than 12, a higher ACL injury rate is reported in boys.
      • Bloom D.A.
      • Wolfert A.J.
      • Michalowitz A.
      • Jazrawi L.M.
      • Carter C.W.
      ACL injuries aren’t just for girls: The role of age in predicting pediatric ACL injury.
      ,
      • Tepolt F.A.
      • Feldman L.
      • Kocher M.S.
      Trends in pediatric ACL reconstruction from the PHIS database.
      ,
      • Kaeding C.C.
      • Flanigan D.
      • Donaldson C.
      Surgical techniques and outcomes after anterior cruciate ligament reconstruction in preadolescent patients.
      • Stracciolini A.
      • Stein C.J.
      • Zurakowski D.
      • et al.
      Anterior cruciate ligament injuries in pediatric athletes presenting to sports medicine clinic: A comparison of males and females through growth and development.
      • Prince J.
      • Laor T.
      • Bean J.
      MRI of anterior cruciate ligament injuries and associated findings in the pediatric knee: Changes with skeletal maturation.
      Increased rates in female athletes begin around puberty,
      • Bloom D.A.
      • Wolfert A.J.
      • Michalowitz A.
      • Jazrawi L.M.
      • Carter C.W.
      ACL injuries aren’t just for girls: The role of age in predicting pediatric ACL injury.
      ,
      • Stracciolini A.
      • Stein C.J.
      • Zurakowski D.
      • et al.
      Anterior cruciate ligament injuries in pediatric athletes presenting to sports medicine clinic: A comparison of males and females through growth and development.
      at around age 12. In both sexes, the rate of ACL injuries increase as they progress through puberty.
      • Bloom D.A.
      • Wolfert A.J.
      • Michalowitz A.
      • Jazrawi L.M.
      • Carter C.W.
      ACL injuries aren’t just for girls: The role of age in predicting pediatric ACL injury.
      ,
      • Tepolt F.A.
      • Feldman L.
      • Kocher M.S.
      Trends in pediatric ACL reconstruction from the PHIS database.
      ,
      • Werner B.C.
      • Yang S.
      • Looney A.M.
      • Gwathmey F.W.
      Trends in pediatric and adolescent anterior cruciate ligament injury and reconstruction.
      ,
      • Stracciolini A.
      • Stein C.J.
      • Zurakowski D.
      • et al.
      Anterior cruciate ligament injuries in pediatric athletes presenting to sports medicine clinic: A comparison of males and females through growth and development.
      The overall injury rate is highest in late adolescence for both sexes (15-18 years).
      • Bloom D.A.
      • Wolfert A.J.
      • Michalowitz A.
      • Jazrawi L.M.
      • Carter C.W.
      ACL injuries aren’t just for girls: The role of age in predicting pediatric ACL injury.
      • Tepolt F.A.
      • Feldman L.
      • Kocher M.S.
      Trends in pediatric ACL reconstruction from the PHIS database.
      • Beck N.A.
      • Lawrence J.T.R.
      • Nordin J.D.
      • DeFor T.A.
      • Tompkins M.
      ACL tears in school-aged children and adolescents over 20 years.
      • Werner B.C.
      • Yang S.
      • Looney A.M.
      • Gwathmey F.W.
      Trends in pediatric and adolescent anterior cruciate ligament injury and reconstruction.
      Periods of rapid growth and development may contribute to ACL injury risk. The femur and tibia grow at a fast rate, which creates a longer lever and increases torque at the knee.
      • LaBella C.R.
      • Hennrikus W.
      • Hewett T.E.
      • et al.
      Anterior cruciate ligament injuries: Diagnosis, treatment, and prevention.
      Increases in height and body weight raise the center of mass, and greater muscle forces are required to control its movement during sports activities leading to increased muscular and neuromuscular demand.
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      • Hennrikus W.
      • Hewett T.E.
      • et al.
      Anterior cruciate ligament injuries: Diagnosis, treatment, and prevention.
      After maturity, decreased biomechanical and neuromuscular control of the knee, such as greater knee abduction angles and moments, higher ground reaction forces during landing, and decreased active knee joint stiffness are observed in females compared to males.
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      • Myer G.D.
      • Hewett T.E.
      Longitudinal effects of maturation on lower extremity joint stiffness in adolescent athletes.
      • Ford K.R.
      • Shapiro R.
      • Myer G.D.
      • Bogert AJ van den
      • Hewett T.E.
      Longitudinal sex differences during landing in knee abduction in young athletes.
      • Hewett T.E.
      • Myer G.D.
      • Ford K.R.
      Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes: A prospective study.
      • Hewett T.E.
      • Myer G.D.
      • Ford K.R.
      Decrease in neuromuscular control about the knee with maturation in female athletes.
      In addition to physical growth, sensorimotor mechanisms such as visual, somatosensory, vestibular, postural control, and coordination continue to develop during childhood and adolescence. Some adolescents may experience delays or regression in some aspects of sensorimotor function, which may affect motor control and contribute to awkward movement patterns. However, there is no consensus on how it may affect injury risk.
      • Quatman-Yates C.C.
      • Quatman C.E.
      • Meszaros A.J.
      • Paterno M.V.
      • Hewett T.E.
      A systematic review of sensorimotor function during adolescence: A developmental stage of increased motor awkwardness?.
      These physical, biomechanical, neuromuscular, and sensorimotor factors may also contribute to a challenging rehabilitation compared to the adult population.
      Nonoperative or delayed surgical treatment was once the standard of care for the skeletally immature patient with ACL tear due to concerns of physeal injury and subsequent deformity. Current practice has evolved to favor early surgery with good functional outcomes, decreased meniscal and articular cartilage injuries, and improved rate of return to sports with minimal risk of growth disturbance.
      • James E.W.
      • Dawkins B.J.
      • Schachne J.M.
      • et al.
      Early operative versus delayed operative versus nonoperative treatment of pediatric and adolescent anterior cruciate ligament injuries: A systematic review and meta-analysis.
      ,
      • Fabricant P.D.
      • Lakomkin N.
      • Cruz A.I.
      • Spitzer E.
      • Lawrence J.T.R.
      • Marx R.G.
      Early ACL reconstruction in children leads to less meniscal and articular cartilage damage when compared with conservative or delayed treatment.
      ,
      • Cordasco F.
      • Mayer S.
      • Green D.
      All-inside, all-epiphyseal anterior cruciate ligament reconstruction in skeletally immature athletes: Return to sport, incidence of second surgery, and 2-year clinical outcomes.
      • Fabricant P.D.
      • Lakomkin N.
      • Cruz A.I.
      • Spitzer E.
      • Marx R.G.
      ACL reconstruction in youth athletes results in an improved rate of return to athletic activity when compared with non-operative treatment: A systematic review of the literature.
      • Ramski D.
      • Kanj W.
      • Franklin C.
      • Baldwin K.
      • Ganley T.
      Anterior cruciate ligament tears in children and adolescents: A meta-analysis of nonoperative versus operative treatment.
      • Frosch K.
      • Stengel D.
      • Brodhun T.
      • et al.
      Outcomes and risks of operative treatment of rupture of the anterior cruciate ligament in children and adolescents.
      Surgical treatment for the skeletally immature includes physeal sparing, partial transphyseal, and transphyseal techniques.
      • Fabricant P.D.
      • Kocher M.S.
      Anterior cruciate ligament injuries in children and adolescents.
      ,
      • Fabricant P.D.
      • Jones K.J.
      • Delos D.
      • et al.
      Reconstruction of the anterior cruciate ligament in the skeletally immature athlete: A review of current concepts AAOS exhibit selection.
      Despite these advancements in surgical treatment, there is currently a lack of evidence-based rehabilitation protocols after ACLR specific to the youth athlete.
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      • Fabricant P.
      • Gornitzky A.
      • et al.
      Rehabilitation following anterior cruciate ligament tears in children.

      Psychosocial Considerations for the Youth Athlete

      Adolescence is a time for identity development, social skill acquisition, and developing independence.
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      ABC of adolescence: Adolescent development.
      Professionals caring for the adolescent athlete must appreciate the impact of injury beyond physical symptoms and functional limitations. Lower quality-of-life (QOL) scores are reported in adolescent athletes with knee injuries
      • McGuine T.A.
      • Winterstein A.P.
      • Carr K.
      • Hetzel S.
      Changes in health-related quality of life and knee function after knee injury in young female athletes.
      ,
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      • Winterstein A.
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      • Hetzel S.
      • Scott J.
      Changes in self-reported knee function and health-related quality of life after knee injury in female athletes.
      with greater impairments in season-ending injuries such as ACL tears.
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      • Kliethermes S.A.
      • et al.
      Impact of in- season injury on quality of life and sleep duration in female youth volleyball athletes: A prospective study of 2073 players.
      A strong correlation between knee function and the social and emotional domains of QOL in pediatric and adolescent patients with ACL injuries has been found both before and after surgery.
      • Boykin R.E.
      • McFeely E.D.
      • Shearer D.
      • et al.
      Correlation between the child health questionnaire and the international knee documentation committee score in pediatric and adolescent patients with an anterior cruciate ligament tear.
      In addition to physical limitations, ACL-injured athletes may experience emotional reactions such as loss, denial, frustration, and anger,
      • Disanti J.
      • Lisee C.
      • Erickson K.
      • Bell D.
      • Shingles M.
      • Kuenze C.
      Perceptions of rehabilitation and return to sport among high school athletes with anterior cruciate ligament reconstruction: A qualitative research study.
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      Young, talented and injured: Injury perceptions, experiences and consequences in adolescent elite athletes.
      • Podlog L.
      • Heil J.
      • Schulte S.
      Psychosocial factors in sports injury rehabilitation and return to play.
      decreased academic performance,
      • Trentacosta N.
      • Vitale M.
      • Ahmad C.
      The effects of timing of pediatric knee ligament surgery on short-term academic performance in school-aged athletes.
      and loss of identity and loneliness.
      • Watson A.
      • Biese K.
      • Kliethermes S.A.
      • et al.
      Impact of in- season injury on quality of life and sleep duration in female youth volleyball athletes: A prospective study of 2073 players.
      ,
      • Von Rosen P.
      • Kottorp A.
      • Fridén C.
      • Frohm A.
      • Heijne A.
      Young, talented and injured: Injury perceptions, experiences and consequences in adolescent elite athletes.
      ,
      • Putukian M.
      The psychological response to injury in student athletes: A narrative review with a focus on mental health.
      Although higher levels of athletic identity are associated with positive health benefits, self-esteem, and improved social relationships, they are also associated with depressive symptoms after injury.
      • Renton T.
      • Petersen B.
      • Kennedy S.
      Investigating correlates of athletic identity and sport-related injury outcomes: A scoping review.
      Moreover, Padaki et al.
      • Padaki A.S.
      • Noticewala M.S.
      • Levine W.N.
      • Ahmad C.S.
      • Popkin M.K.
      • Popkin C.A.
      Prevalence of posttraumatic stress disorder symptoms among young athletes after anterior cruciate ligament rupture.
      reported that many adolescent athletes experienced symptoms consistent with post-traumatic stress disorder after an ACL rupture, suggesting that the level of psychological trauma experienced by these athletes may be greater than is recognized. Healthcare professionals must appreciate the unique psychosocial factors that impact injured youth athletes and should prioritize their psychological and emotional well-being when caring for their physical health. To maintain social aspects, young athletes may be encouraged to attend and participate in their team training sessions as their surgical precautions allow.
      • Ardern C.L.
      • Ekås G.R.
      • Grindem H.
      • et al.
      2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries.
      Although depressive symptoms may decrease over time,
      • Podlog L.
      • Heil J.
      • Schulte S.
      Psychosocial factors in sports injury rehabilitation and return to play.
      ,
      • Manuel J.C.
      • Shilt J.S.
      • Curl W.W.
      • et al.
      Coping with sports injuries: An examination of the adolescent athlete.
      psychological response after an injury varies among individuals
      • Podlog L.
      • Heil J.
      • Schulte S.
      Psychosocial factors in sports injury rehabilitation and return to play.
      ; therefore referral to sport psychology may be warranted for the struggling athlete for successful rehabilitation.
      Psychological factors must also be considered during recovery after ACLR. Factors such as anxiety may affect recovery in children. High levels of preoperative anxiety in children and adolescents are related to higher postoperative pain intensity.
      • Chieng Y.
      • Chan W.
      • Klainin-Yobas P.
      • He H.
      Perioperative anxiety and postoperative pain in children and adolescents undergoing elective surgical procedures: A quantitative systematic review.
      Perioperative parental anxiety and pain catastrophizing also relate to child anxiety and postoperative pain,
      • Kain Z.
      • Mayes L.
      • Weisman S.
      • Hofstadter M.
      Social adaptability, cognitive abilities, and other predictors for children’s reactions to surgery.
      • Kain Z.
      • Mayes L.
      • O’Connor T.
      • Cicchetti D.
      Preoperative anxiety in children. Predictors and outcomes.
      • Rabbitts J.
      • Groenewalkd C.
      • Tai G.
      • Palermo T.
      Presurgical psychosocial predictors of acute postsurgical pain and quality of life in children undergoing major surgery.
      highlighting the influence of parents on the child, unique to this population. Anxiety and pain can negatively affect rehabilitation because patients may not tolerate weightbearing loads and range of motion progressions and may find it difficult to adhere to home exercise programs or to be motivated. Youth athletes, especially prepubescents, cannot perform unsupervised exercises independently with correct technique.
      • Ardern C.L.
      • Ekås G.R.
      • Grindem H.
      • et al.
      2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries.
      Successful rehabilitation and adherence to home programs often require collaboration with parents or family members, even in the adolescent population.
      The healthcare team plays an important role for youth during their recovery. Disanti reported psychological and social barriers were just as prevalent as physical symptoms for returning to physical activity. Positive factors that help with recovery include having detailed knowledge of their recovery process, trusting relationships with the physical therapist (PT), individualized goals, and incorporating sport-specific activities. Negative factors include lack of attention from the medical team and receiving a generalized approach to treatment.
      • Disanti J.
      • Lisee C.
      • Erickson K.
      • Bell D.
      • Shingles M.
      • Kuenze C.
      Perceptions of rehabilitation and return to sport among high school athletes with anterior cruciate ligament reconstruction: A qualitative research study.
      Paterno et al.
      • Paterno M.V.
      • Schmitt L.C.
      • Thomas S.
      • Duke N.
      • Russo R.
      • Quatman-Yates C.C.
      Patient and parent perceptions of rehabilitation factors that influence outcomes after anterior cruciate ligament reconstruction and clearance to return to sport in adolescents and young adults.
      identified PT/patient relationship quality as an essential factor that young patients and their parents perceive to impact ACLR outcomes. PTs are identified as a guide throughout the recovery process, motivator, confidence booster, and care coordinator.
      • Paterno M.V.
      • Schmitt L.C.
      • Thomas S.
      • Duke N.
      • Russo R.
      • Quatman-Yates C.C.
      Patient and parent perceptions of rehabilitation factors that influence outcomes after anterior cruciate ligament reconstruction and clearance to return to sport in adolescents and young adults.
      Based on the information, the healthcare team may provide athletes with thorough education on the overall recovery process in easily understandable ways, create and discuss individualized treatment plans and goals with the patient, and ensure one-on-one attention during their sessions. Postoperative rehabilitation can be frustrating and mentally challenging for the ordinarily active young athlete, especially in the early stages when the athlete performs relatively basic exercises. Incorporating sport-specific exercises throughout the recovery process and providing the athlete with challenging workouts with aerobic conditioning, involving the upper extremities or the uninjured leg within safe constraints can help motivate and keep them engaged. Providing the athlete with concrete short-term goals (e.g., 1 session or 1 week) and assessing them with the patient may also help them navigate the uncertainty they may have about their progress and motivate them for the next goal. Although it is common for youth athletes and rehabilitation specialists to become impatient and frustrated with the slow progress, adhering to both time- and criterion-based progression is advocated.
      • Yellin J.
      • Fabricant P.
      • Gornitzky A.
      • et al.
      Rehabilitation following anterior cruciate ligament tears in children.

      Rehabilitation is Slower in the Youth Athlete

      Recovery for the youth athlete after ACLR is typically slower than that of an adult because of postsurgical precautions, slower strength gains, and psychological factors. Physeal-respecting surgeries frequently have weightbearing and range of motion restrictions,
      • Fabricant P.D.
      • Kocher M.S.
      Anterior cruciate ligament injuries in children and adolescents.
      ,
      • Yellin J.
      • Fabricant P.
      • Gornitzky A.
      • et al.
      Rehabilitation following anterior cruciate ligament tears in children.
      contributing to a longer rehabilitation duration. Concomitant procedures to the meniscus or the articular cartilage can further prolong this process.
      Quadriceps strength deficit is related to altered knee mechanics, greater limb asymmetry, altered landing patterns,
      • Schmitt L.
      • Paterno M.
      • Ford K.
      • Myer G.
      • Hewett T.
      Strength asymmetry and landing mechanics at return to sport after ACL reconstruction.
      and decreased function
      • Schmitt L.
      • Paterno M.
      • Hewett T.
      The impact of quadriceps femoris strength asymmetry on functional performance at return to sport following anterior cruciate ligament reconstruction.
      after ACLR. Delayed strength recovery is reported in all age groups in the pediatric population. In preadolescent athletes who underwent all-epiphyseal physeal-sparing ACLR, only 56% of athletes achieved 90% quad strength symmetry at 7 months after ACLR whereas 94% of athletes achieved adequate hamstring strength.
      • Greenberg E.M.
      • Greenberg E.T.
      • Ganley T.J.
      • Lawrence J.T.R.
      Strength and functional performance recovery after anterior cruciate ligament reconstruction in preadolescent athletes.
      In contrast, a separate study of pediatric athletes who underwent the same surgery reported that 69% of athletes met 90% limb symmetry for quadriceps strength, whereas only 38% met the cutoff for hamstring strength.
      • Ithurburn M.P.
      • Paljieg A.
      • Thomas S.
      • Hewett T.E.
      • Paterno M.V.
      • Schmitt L.C.
      Strength and function across maturational levels in young athletes at the time of return to sport after ACL reconstruction.
      Difficulty regaining strength is also reported in adolescents, with only 59% of athletes (mean age 15) achieving ≥85% quadriceps symmetry within 6 months.
      • Wells L.
      • Dyke J.A.
      • Albaugh J.
      • Ganley T.
      Adolescent anterior cruciate ligament reconstruction: A retrospective analysis of quadriceps strength recovery and return to full activity after surgery.
      Additionally, in older adolescents (mean age 17) who were cleared for unrestricted sports, only 43.5% to 56% met the cutoff of 85% to 90% quadriceps strength symmetry.
      • Schmitt L.
      • Paterno M.
      • Ford K.
      • Myer G.
      • Hewett T.
      Strength asymmetry and landing mechanics at return to sport after ACL reconstruction.
      ,
      • Schmitt L.
      • Paterno M.
      • Hewett T.
      The impact of quadriceps femoris strength asymmetry on functional performance at return to sport following anterior cruciate ligament reconstruction.
      ,
      • Toole A.R.
      • Ithurburn M.P.
      • Rauh M.J.
      • Hewett T.E.
      • Paterno M.V.
      • Schmitt L.C.
      Young athletes cleared for sports participation after anterior cruciate ligament reconstruction: How many actually meet recommended return-to-sport criterion cutoffs?.
      Although the cause of this delay in strength recovery is unclear, it is thought that physiological and psychological factors contribute. Training-induced strength improvements can be achieved in prepubescent children.
      • Granacher U.
      • Goesele A.
      • Roggo K.
      • et al.
      Effects and mechanisms of strength training in children.
      ,
      • Behringer M.
      • Heede A vom
      • Matthews M.
      • Mester J.
      Effects of strength training on motor performance skills in children and adolescents: A meta-analysis.
      However, strength gain is likely related to improved motor unit recruitment and neural adaptations rather than muscle hypertrophy
      • Ramsay J.
      • Blimkie C.
      • Smith K.
      • Garner S.
      • MacDougall J.
      • Sale D.
      Strength training effects in prepubescent boys.
      ,
      • Lloyd R.S.
      • Oliver J.L.
      The youth physical development model: A new approach to long-term athletic development.
      because they lack androgenic hormones.
      • Murray P.
      • Playton P.
      Endocrine control of growth.
      ,
      • Round J.
      • Jones D.
      • Honour J.
      • Nevill A.
      Hormonal factors in the development of differences in strength between boys and girls during adolescence: A longitudinal study.
      Thus, in this age group, dynamic multijoint neuromuscular control should be the primary focus in rehabilitation.
      • Ardern C.L.
      • Ekås G.R.
      • Grindem H.
      • et al.
      2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries.
      In adolescence, there is an increase in circulating androgens
      • Murray P.
      • Playton P.
      Endocrine control of growth.
      ; therefore rehabilitation can more closely resemble that of an adult.
      • Ardern C.L.
      • Ekås G.R.
      • Grindem H.
      • et al.
      2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries.
      As discussed previously, increased postoperative pain and anxiety may contribute to slow recovery of strength and functional progression. Furthermore, psychological readiness is increasingly recognized as influencing RTS after ACLR.
      • Kaplan Y.
      • Witvrouw E.
      When is it safe to return to sport after ACL reconstruction? Reviewing the criteria.
      • Christino M.A.
      • Fantry A.J.
      • Vopat B.G.
      Psychological aspects of recovery following anterior cruciate ligament reconstruction.
      • Ardern C.L.
      • Taylor N.F.
      • Feller J.A.
      • Whitehead T.S.
      • Webster K.E.
      Psychological responses matter in returning to preinjury level of sport after anterior cruciate ligament reconstruction surgery.
      • McCullough K.
      • Phelps K.
      • Spindler K.
      • et al.
      Return to high school- and college-level football after anterior cruciate ligament reconstruction: A Multicenter Orthopaedic Outcomes Network (MOON) cohort study.
      • Kvist J.
      • Ek A.
      • Sporrstedt K.
      • Good L.
      Fear of re-injury: A hindrance for returning to sports after anterior cruciate ligament reconstruction.
      Paterno et al.
      • Paterno M.V.
      • Flynn K.
      • Thomas S.
      • Schmitt L.C.
      Self-reported fear predicts functional performance and second ACL Injury after ACL reconstruction and return to sport: A pilot study.
      reported those with greater self-reported fear, using the Tampa Scale of Kinesiophobia, demonstrated decreased single-leg hop performance, isometric quadriceps strength, and had an increased risk of ipsilateral reinjury in the 24 months after ACLR. McPherson et al.
      • McPherson A.L.
      • Feller J.A.
      • Hewett T.E.
      • Webster K.E.
      Smaller change in psychological readiness to return to sport is associated with second anterior cruciate ligament injury among younger patients.
      reported those with minor improvement in psychological readiness from preoperative to the 12-month mark, as measured by ACL-Return to Sport after Injury (ACL-RSI), were associated with a second ACL injury in younger patients. Although the specific recommendations of psychological interventions is beyond the scope of this article and can be found elsewhere,
      • te Wierike S.C.M.
      • van der Sluis A.
      • van den Akker-Scheek I.
      • Elferink-Gemser M.T.
      • Visscher C.
      Psychosocial factors influencing the recovery of athletes with anterior cruciate ligament injury: A systematic review.
      it is important for clinicians to address psychological factors throughout the rehabilitation process.

      Return to Sport Testing for the Youth

      Most agree on using a battery of tests to assess RTS readiness, including muscle strength tests, functional tests such as hop tests, movement quality, and patient-reported outcome measures (PROMs).
      • Dietvorst M.
      • Brzoskowski M.H.
      • van der Steen M.
      • Delvaux E.
      • Janssen R.P.A.
      • Van Melick N.
      Limited evidence for return to sport testing after ACL reconstruction in children and adolescents under 16 years: A scoping review.
      • Capin J.J.
      • Snyder-Mackler L.
      • Risberg M.A.
      • Grindem H.
      Keep calm and carry on testing: A substantive reanalysis and critique of “What is the evidence for and validity of return-to-sport testing after anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis.”.
      • Burgi C.R.
      • Peters S.
      • Ardern C.L.
      • et al.
      Which criteria are used to clear patients to return to sport after primary ACL reconstruction? A scoping review.
      Limb symmetry index ≥90% is a frequently reported criterion for strength and functional tests. Still, only 13% to 25% meet the passing combined criteria in this population after ACLR.
      • Greenberg E.M.
      • Greenberg E.T.
      • Ganley T.J.
      • Lawrence J.T.R.
      Strength and functional performance recovery after anterior cruciate ligament reconstruction in preadolescent athletes.
      ,
      • Toole A.R.
      • Ithurburn M.P.
      • Rauh M.J.
      • Hewett T.E.
      • Paterno M.V.
      • Schmitt L.C.
      Young athletes cleared for sports participation after anterior cruciate ligament reconstruction: How many actually meet recommended return-to-sport criterion cutoffs?.
      Interestingly, Greenberg et al.
      • Greenberg E.M.
      • Dyke J.
      • Leung A.
      • Karl M.
      • Lawrence J.T.
      • Ganley T.
      Uninjured youth athlete performance on single-leg hop testing: How many can achieve recommended return-to-sport criterion?.
      reported that although a high proportion of uninjured youth athletes achieved passing performance on isolated hop tests, only 45% achieved ≥90% limb symmetry index across all four hop tests. These studies suggest that hop tests should be used with caution in this population.
      The use of the uninvolved limb as a reference standard for symmetry presents its own problem. It does not reflect preinjury levels and may overestimate knee function after ACLR,
      • Wellsandt E.
      • Failla M.
      • Snyder-Mackler L.
      Limb symmetry indexes can overestimate knee function after ACL injury.
      because of contralateral leg detraining, or the leg was weaker to begin with. The contralateral leg may be best tested before surgery for a more accurate benchmark.
      • Davies W.T.
      • Myer G.D.
      • Read P.J.
      Is it time we better understood the tests we are using for return to sport decision making following ACL reconstruction? A critical review of the hop tests.
      In addition to quantitative measures, quality of movement should be assessed as part of the RTS decision-making process. Decreased neuromuscular control has been related to ACL injury, reinjury, and decreased knee function.
      • Ithurburn M.P.
      • Paterno M.V.
      • Ford K.R.
      • Hewett T.E.
      • Schmitt L.C.
      Young athletes after anterior cruciate ligament reconstruction with single-leg landing asymmetries at the time of return to sport demonstrate decreased knee function 2 years later.
      • Paterno M.V.
      • Schmitt L.C.
      • Ford K.R.
      • et al.
      Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport.
      • Pollard C.D.
      • Sigward S.M.
      • Powers C.M.
      Limited hip and knee flexion during landing is associated with increased frontal plane knee motion and moments.
      Movements such as squat, step down, single leg squat, drop vertical jump, tuck jump, deceleration, shuffle, single leg hop, and cutting are commonly used to assess kinematics and loading symmetry.
      • Ellington M.D.
      • Randich K.
      • Garfin J.
      • et al.
      Interrater and intrarater reliability and discriminant validity of a pediatric lower extremity physical therapy clearance test.
      ,
      • Graziano J.
      • Chiaia T.
      • De Mille P.
      • Nawabi D.H.
      • Green D.W.
      • Cordasco F.A.
      Return to sport for skeletally immature athletes after ACL reconstruction: Preventing a second injury using a quality of movement assessment and quantitative measures to address modifiable risk factors.
      There is currently no standardized testing procedure for the pediatric athlete, and protocols created for the adult may lead to inaccurate results. Children may require verbal and visual demonstrations of the tasks, repeated several times, as well as specific instructions so that they clearly understand what they are asked to do. Different testing criteria and testing procedure may be necessary for the youth athlete.
      Physical tests alone do not provide a complete picture of an athlete’s readiness to RTS. PROMs offer insight into patient's perception of recovery and are an integral component of information in addition to objective clinical data throughout the recovery process. Phillips reported PROMs are underused and misused in the pediatric orthopaedic literature.
      • Phillips L.
      • Carsen S.
      • Vasireddi A.
      • Mulpuri K.
      Use of patient-reported outcome measures in pediatric orthopaedic literature.
      Fabricant found the use of PROMs to evaluate pediatric ACLR is neither standardized nor validated for the population.
      • Fabricant P.D.
      • Brusalis C.M.
      • Schachne J.M.
      • et al.
      Which metrics are being used to evaluate children and adolescents after ACL reconstruction? A systematic review.
      The Lysholm, International Knee Documentation Committee Subjective Knee form (IKDC), Tegner Activity Scale, and Knee Injury and Osteoarthritis Outcome Score (KOOS) are frequently reported PROMs in the pediatric ACL literature,
      • Fabricant P.D.
      • Brusalis C.M.
      • Schachne J.M.
      • et al.
      Which metrics are being used to evaluate children and adolescents after ACL reconstruction? A systematic review.
      ,
      • Zebis M.K.
      • Warming S.
      • Pedersen M.B.
      • et al.
      Outcome measures after ACL Injury in pediatric patients: A scoping review.
      but none are designed for nor validated in the pediatric population. The use of adult PROMs in children has been shown to cause comprehensibility problems and should be avoided.
      • Dietvorst M.
      • Reijman M.
      • Groningen B van
      • Steen MC van der
      • Janssen R.P.A.
      PROMs in paediatric knee ligament injury: Use the Pedi-IKDC and avoid using adult PROMs.
      Therefore, whenever possible, the use of pediatric PROMs is recommended, such as the Pedi-IKDC
      • Kocher M.
      • Smith J.
      • Iversen M.
      • et al.
      Reliability, validity, and responsiveness of a modified International Knee Documentation Committee Subjective Knee Form (Pedi-IKDC) in children with knee disorders.
      ,
      • van der Velden C.
      • van der Steen M.
      • Leenders J.
      • van Douveren F.
      • Janssen R.
      • Reijman M.
      Pedi-IKDC or KOOS-child: Which questionnaire should be used in children with knee disorders?.
      or KOOS-Child
      • Ortqvist M.
      • Iversen M.
      • Janarv P.
      • Broström E.
      • Roos E.
      Psychometric properties of the Knee injury and Osteoarthritis Outcome Score for Children (KOOS-Child) in children with knee disorders.
      to assess self-reported knee function, and the Hospital for Special Surgery Pediatric Functional Activity Brief Scale (HSS Pedi-FABS)
      • Fabricant P.
      • Robles A.
      • Downey-Zayas T.
      • et al.
      Development and validation of a pediatric sports activity rating scale: The Hospital for Special Surgery Pediatric Functional Activity Brief Scale (HSS Pedi-FABS).
      to assess self-reported activity level. The Child Health Questionnaire,
      • Hullmann S.
      • Ryan J.
      • Ramsey R.
      • Chaney J.
      • Mullins L.
      Measures of general pediatric quality of life: Child Health Questionnaire (CHQ), DISABKIDS Chronic Generic Measure (DCGM), KINDL-R, Pediatric Quality of Life Inventory (PedsQL) 4.0 Generic Core Scales, and Quality of My Life Questionnaire (QoML).
      Peds QL,
      • Varni J.
      • Seid M.
      • Rode C.
      The PedsQL: Measurement model for the pediatric quality of life inventory.
      or the Pediatric PROMIS
      • Irwin D.
      • Varni J.
      • Yeatts K.
      • DeWalt D.
      Cognitive interviewing methodology in the development of a pediatric item bank: A patient reported outcomes measurement information system (PROMIS) study.
      may be used to assess QOL.
      Incorporating psychological readiness and kinesiophobia assessment into a battery of RTS tests can further assist clinicians in RTS decision-making. The ACL-RSI assesses emotion, confidence, and risk appraisal and has been related to decision to RTS.
      • Webster K.E.
      • Feller J.A.
      • Lambros C.
      Development and preliminary validation of a scale to measure the psychological impact of returning to sport following anterior cruciate ligament reconstruction surgery.
      Additionally, a cutoff score of 76.7 points was 90% sensitive to identify younger patients who suffered a second ACL injury.
      • McPherson A.L.
      • Feller J.A.
      • Hewett T.E.
      • Webster K.E.
      Psychological readiness to return to sport Is associated with second anterior cruciate ligament injuries.
      ACL-RSI is valid from 16 years of age.
      • Webster K.E.
      • Feller J.A.
      • Lambros C.
      Development and preliminary validation of a scale to measure the psychological impact of returning to sport following anterior cruciate ligament reconstruction surgery.
      The Tampa Scale of Kinesiophobia assesses pain-related fear or movement or reinjury and has been used in previous studies after ACLR.
      • Paterno M.V.
      • Flynn K.
      • Thomas S.
      • Schmitt L.C.
      Self-reported fear predicts functional performance and second ACL Injury after ACL reconstruction and return to sport: A pilot study.
      ,
      • George S.Z.
      • Lentz T.A.
      • Zeppieri G.J.
      • Lee D.
      • Chmielewski T.L.
      Analysis of shortened versions of the Tampa Scale for Kinesiophobia and Pain Catastrophizing Scale for patients following anterior cruciate ligament reconstruction.
      However, it is important to note that the instrument has not been validated for children after ACLR.

      Reinjury Rate is High in the Youth

      Testing both physical and psychological readiness is important before RTS because reinjury rate is high. More than 90% of pediatric athletes return to sport after ACLR, with up to 81% returning to competitive-level sport at the preinjury level.
      • Kay J.
      • Memon M.
      • Marx R.G.
      • Peterson D.
      • Simunovic N.
      • Ayeni O.R.
      Over 90 % of children and adolescents return to sport after anterior cruciate ligament reconstruction: A systematic review and meta-analysis.
      ,
      • Morvan A.
      • Bouguennec N.
      • Graveleau N.
      ACL injuries before 15 years of age: Could the young become an athlete?.
      However, the rate of a second ACL injury in this population is as high as 32%.
      • Paterno M.V.
      • Rauh M.J.
      • Schmitt L.C.
      • Ford K.R.
      • Hewett T.E.
      Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport.
      ,
      • Wiggins A.
      • Grandhi R.
      • Schneider D.
      • Stanfield D.
      • Webster K.
      • Myer G.
      Risk of secondary injury in younger athletes after anterior cruciate ligament reconstruction: A systematic review and meta-analysis.
      • Paterno M.V.
      • Rauh M.J.
      • Schmitt L.C.
      • Ford K.R.
      • Hewett T.E.
      Incidence of contralateral and ipsilateral anterior cruciate ligament (ACL) injury after primary ACL reconstruction and return to sport.
      • Webster K.E.
      • Feller J.A.
      • Leigh W.B.
      • Richmond A.K.
      Younger patients are at increased risk for graft rupture and contralateral injury after anterior cruciate ligament reconstruction.
      The risk is highest within the first 2 years after ACLR.
      • Paterno M.V.
      • Rauh M.J.
      • Schmitt L.C.
      • Ford K.R.
      • Hewett T.E.
      Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport.
      ,
      • Webster K.E.
      • Feller J.A.
      Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction.
      Unfortunately, the contralateral injury rate in this population is also increased, at 7% to 20.5%.
      • Dekker T.J.
      • Godin J.A.
      • Dale K.M.
      • Garrett W.E.
      • Taylor D.C.
      • Riboh J.C.
      Return to sport after pediatric anterior cruciate ligament reconstruction and its effect on subsequent anterior cruciate ligament injury.
      ,
      • Paterno M.V.
      • Rauh M.J.
      • Schmitt L.C.
      • Ford K.R.
      • Hewett T.E.
      Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport.
      ,
      • Paterno M.V.
      • Rauh M.J.
      • Schmitt L.C.
      • Ford K.R.
      • Hewett T.E.
      Incidence of contralateral and ipsilateral anterior cruciate ligament (ACL) injury after primary ACL reconstruction and return to sport.
      ,
      • Patel N.M.
      • Bram J.T.
      • Talathi N.S.
      • Defrancesco C.J.
      • Lawrence J.T.R.
      • Ganley T.J.
      Which children are at risk for contralateral anterior cruciate ligament injury after ipsilateral reconstruction?.
      • Ho B.
      • Edmonds E.
      • Chambers H.
      • Bastrom T.
      • Pennock A.
      Risk factors for early ACL reconstruction failure in pediatric and adolescent patients: A review of 561 cases.
      • DeFrancesco C.J.
      • Storey E.P.
      • Flynn J.M.
      • Ganley T.J.
      Pediatric ACL reconstruction and return to the operating room: Revision Is less than half of the story.
      Reasons for a second ACL injury to either knee is multifactorial. Non-modifiable factors include graft type,
      • Rugg C.M.
      • Pitcher A.A.
      • Allen C.
      • Pandya N.K.
      Revision ACL reconstruction in adolescent patients.
      ,
      • Engelman G.
      • Carry P.
      • Hitt K.
      • Polousky J.
      • Vidal A.
      Comparison of allograft versus autograft anterior cruciate ligament reconstruction graft survival in an active adolescent cohort.
      ,
      • Ellis H.B.
      • Matheny L.M.
      • Briggs K.K.
      • Pennock A.T.
      • Steadman J.R.
      Outcomes and revision rate after bone-patellar tendon-bone allograft versus autograft anterior cruciate ligament reconstruction in patients aged 18 years or younger with closed physes.
      age younger than 15 to 16,
      • Patel N.M.
      • Bram J.T.
      • Talathi N.S.
      • Defrancesco C.J.
      • Lawrence J.T.R.
      • Ganley T.J.
      Which children are at risk for contralateral anterior cruciate ligament injury after ipsilateral reconstruction?.
      ,
      • Astur D.C.
      • Cachoeira C.M.
      • Vieira T da S
      • Debieux P.
      • Kaleka C.C.
      • Cohen M.
      Increased incidence of anterior cruciate ligament revision surgery in paediatric verses adult population.
      female sex,
      • Patel N.M.
      • Bram J.T.
      • Talathi N.S.
      • Defrancesco C.J.
      • Lawrence J.T.R.
      • Ganley T.J.
      Which children are at risk for contralateral anterior cruciate ligament injury after ipsilateral reconstruction?.
      and anatomic factors.
      • Dare D.
      • Fabricant P.
      • McCarthy M.
      • et al.
      Increased lateral tibial slope is a risk factor for pediatric anterior cruciate ligament injury: An MRI-based case-control study of 152 patients.
      • O’Malley M.
      • Milewski M.
      • Solomito M.
      • Erwteman A.
      • Nissen C.
      The association of tibial slope and anterior cruciate ligament rupture in skeletally immature patients.
      • Shaw K.
      • Dunoski B.
      • Mardis N.
      • Pacicca D.
      Knee morphometric risk factors for acute anterior cruciate ligament injury in skeletally immature patients.
      Modifiable factors include returning to high-risk sports
      • Webster K.E.
      • Feller J.A.
      • Kimp A.J.
      • Whitehead T.S.
      Revision anterior cruciate ligament reconstruction outcomes in younger patients: Medial meniscal pathology and high rates of return to sport are associated with third ACL injuries.
      and biomechanical and neuromuscular factors.
      • Paterno M.V.
      • Schmitt L.C.
      • Ford K.R.
      • et al.
      Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport.
      Decreased net hip muscle external rotation torque, increased dynamic valgus during landing, asymmetries in internal knee extensor moment at initial contact, and decreased single-leg postural stability at the time of RTS predicts second ACL injury to either knee.
      • Paterno M.V.
      • Schmitt L.C.
      • Ford K.R.
      • et al.
      Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport.
      These neuromuscular deficits are similar to primary ACL injury risk.
      • Hewett T.E.
      • Myer G.D.
      • Ford K.R.
      Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes: A prospective study.
      Neuromuscular training (NMT) effectively improves landing mechanics and performance and has shown to reduce ACL injury rate in healthy adolescents.
      • Hewett T.E.
      • Lindenfeld T.
      • Riccobene J.
      • Noyes F.
      The effect of neuromuscular training on the incidence of knee injury in female athletes: A prospective study.
      • Noyes F.
      • Barber-Westin S.
      Neuromuscular retraining intervention programs: Do they reduce noncontact anterior cruciate ligament injury rates in adolescent female athletes?.
      • Sugimoto D.
      • Myer G.D.
      • Bush H.M.
      • Klugman M.F.
      • McKeon J.M.M.
      • Hewett T.E.
      Compliance with neuromuscular training and anterior cruciate ligament injury risk reduction in female athletes: A meta-analysis.
      • Myer G.
      • Ford K.
      • Palumbo J.
      • Hewett T.
      Neuromuscular training improves performance and lower-extremity biomechanics in female athletes.
      • Hewett T.E.
      • Myer G.D.
      Reducing knee and anterior cruciate ligament injuries among female athletes.
      • Myer G.D.
      • Sugimoto D.
      • Thomas S.
      • Hewett T.E.
      The influence of age on the effectiveness of neuromuscular training to reduce anterior cruciate ligament injury in female athletes: A meta-analysis.
      Therefore NMT program should be an important component of rehabilitation after ACLR to reduce the risk of a second injury to the ipsilateral leg and to the contralateral leg. NMT effectiveness on preventing ACL injury has been shown to be dose-dependent and should be performed longer than 20 minutes in duration, more than 2 times per week.
      • D S.
      • GD M.
      • KD B.F.
      • MJ P.
      • LJ M.
      • TE H.
      Critical components of neuromuscular training to reduce ACL injury risk in female athletes: Meta-regression analysis.
      Incorporating various types of exercises such as plyometrics, balance training, trunk stabilization, and posterior chain strengthening exercises optimize the effects of NMT.
      • D S.
      • GD M.
      • KD B.F.
      • MJ P.
      • LJ M.
      • TE H.
      Critical components of neuromuscular training to reduce ACL injury risk in female athletes: Meta-regression analysis.
      Clinic-based rehabilitation may not represent the same conditions athletes experience on the field or court during sports. Therefore youth athletes may benefit from a more performance-based, sports-specific RTS training before unrestricted sports participation. On-field rehabilitation and RTS training programs have been shown to successfully improve muscle strength and knee function and reduce the risk of reinjury after ACLR.
      • Della Villa S.
      • Boldrini L.
      • Ricci M.
      • et al.
      Clinical outcomes and return-to-sports participation of 50 soccer players after anterior cruciate ligament reconstruction through a sport-specific rehabilitation protocol.
      • Della Villa F.
      • Ricci M.
      • Perdisa F.
      • et al.
      Anterior cruciate ligament reconstruction and rehabilitation: Predictors of functional outcome.
      • Capin J.J.
      • Failla M.
      • Zarzycki R.
      • et al.
      Superior 2-Year functional outcomes among young female athletes after ACL reconstruction in 10 return-to-sport training sessions: Comparison of ACL-SPORTS randomized controlled trial with Delaware-Oslo and MOON cohorts.
      Important elements include restoring movement quality, physical conditioning, sport-specific skills, and load management.
      • Buckthorpe M.
      • Villa F Della
      • Villa S Della
      • Roi G.S.
      On-field rehabilitation part 1: 4 pillars of high-quality on-field rehabilitation are restoring movement quality, physical conditioning, restoring sport-specific skills, and progressively developing chronic training load.
      This may be best performed working with a performance specialist or team coach. Communication of all key stakeholders (athlete, coach, parents/guardians, healthcare providers) is crucial to monitor the progress of the program and assist the athlete’s safe RTS. A more rigorous RTS training program that bridges the gap between rehabilitation and unrestricted sports may improve outcomes after ACLR in the youth.

      Time to Return to Sport is Later in Youth Athletes

      Many young athletes expect to RTS much sooner than the expected timeline.
      • Armento A.
      • Albright J.
      • Gagliardi A.
      • Daoud A.K.
      • Howell D.
      • Mayer S.
      Patient expectations and perceived social support related to return to sport after anterior cruciate ligament reconstruction in adolescent athletes.
      There are considerable differences in the literature regarding time to RTS in this population, and the appropriate time to return to play is currently unknown. Earlier RTS has been shown to be predictive of a second ACL injury in youth athletes.
      • Dekker T.J.
      • Godin J.A.
      • Dale K.M.
      • Garrett W.E.
      • Taylor D.C.
      • Riboh J.C.
      Return to sport after pediatric anterior cruciate ligament reconstruction and its effect on subsequent anterior cruciate ligament injury.
      ACL reinjury rate was reduced by 51% for each month RTS was delayed until 9 months after surgery.
      • Grindem H.
      • Snyder-Mackler L.
      • Moksnes H.
      • Engebretsen L.
      • Risberg M.A.
      Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: The Delaware-Oslo ACL cohort study.
      Additionally, young athletes who returned to sport earlier than nine months had a 7-fold higher rate of second ACL injury than those who returned to sport after 9 months.
      • Beischer S.
      • Gustavsson L.
      • Senorski E.
      • et al.
      Young athletes who return to sport before 9 months after anterior cruciate ligament reconstruction have a rate of new injury 7 times that of those who delay return.
      The International Olympic Committee recommends youth athletes delay returning to pivoting sport until at least 12 months,
      • Ardern C.L.
      • Ekås G.R.
      • Grindem H.
      • et al.
      2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries.
      and Nagelli and Hewitt
      • Nagelli C.V.
      • Hewett T.E.
      Should return to sport be delayed until two years after anterior cruciate ligament reconstruction? Biological and functional considerations.
      proposed that young athletes delay RTS for two years based on biological healing, resolution of symptoms, and functional recovery. Based on the present information, RTS may be considered beginning at 9 months and can be as late as 2 years, along with satisfactory objective clinical data, movement quality, and psychological readiness. Healthcare providers should educate the athlete and their families regarding realistic expectations for time to RTS and risks of returning to sport too soon in a manner that is easily understandable before surgery.
      It is important to note that many articles on pediatric and adolescent ACL injuries are of level IV evidence. Moreover, most are published after 2000 with short-term follow-up. Therefore the long-term functional outcome and QOL are largely unknown.

      Conclusion

      Successfully returning a youth athlete to sport after ACLR requires knowledge and appreciation of various aspects of the growing athlete different from adults. In addition to postoperative precautions that contribute to a slow rehabilitation process, young athletes need additional time for strength gains. Address risk of reinjury and for contralateral injury by using neuromuscular training and rigorous return to sport training programs. Consider return to sport after 9 months as reinjury rate is high in this population. A combination of time and objective measures, both quantitative and qualitative criteria, and psychological readiness should be used to assess readiness to return to sport and decrease risk of future injury. Healthcare providers should be aware of the psychosocial impact of injury on the youth athletes and refer to sport psychology when necessary.

      Supplementary Data

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