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Pediatric ACL Tears: Natural History

Dingel, Aleksei BS*; Aoyama, Julien BS; Ganley, Ted MD; Shea, Kevin MD*

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Journal of Pediatric Orthopaedics: July 2019 - Volume 39 - Issue - p S47-S49
doi: 10.1097/BPO.0000000000001367
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Participation in youth sports, sports intensity, and early sports specialization has increased over the past 30 years. Year-round-training,1 longer practice sessions, and entering sports at a younger age2 are all common occurrences today. These factors have led to an increase in injuries in pediatric patients, particularly anterior cruciate ligament (ACL) tears in skeletally immature athletes.3,4 Numerous epidemiologic studies have demonstrated an increase in both tibial spine fractures and ACL tears in the pediatric population over the last 20 years.5–8 The purpose of this article was to report on the natural history of ACL injuries in the skeletally immature.


A review of published literature on pediatric, skeletally immature ACL tears and “conservative,” nonoperative treatment was conducted via Pubmed articles published from 1970 to 2018. The search criteria included the key terms “anterior cruciate ligament,” “pediatric” and/or “adolescent,” and “conservative” and/or “nonoperative treatment.” A PRISMA workflow was used to narrow down the articles to those relevant to our analysis and available in full text format.


In 1988, McCarroll and colleagues conducted a prospective study of 40 skeletally immature patients with open physes undergoing either operative (24 patients) or nonoperative care (16 patients) for a mid-substance ACL rupture. After an average follow-up of 2.5 years, they found that only 7 of the 16 nonoperatively treated patients had returned to sports and all 16 reported recurrent episodes of giving way, effusions, and pain. Conversely, all of the 24 patients who underwent ACL reconstruction (10 I.T. band, 14 patellar tendon) returned to sport and 22 of the 24 were still competing at the 2.5 year follow-up. One of the 24 had reinjured the meniscus and another had reinjured the ACL. No patients from the surgical group sustained leg length discrepancy. McCarroll et al9 concluded that the athletic desires of the patient should be used as an indication as to whether operative or nonoperative treatment route is best for the patient.

In 1995, Mizuta and colleagues reported on 18 skeletally immature patients with ACL tears all treated nonoperatively. At the time of follow-up only 1 patient had returned to the same level of preinjury athletics, and the overall functional scores were fair to poor in 16/18 patients. They concluded that the results of nonoperative treatment yielded poor, unacceptable results.10

In 2013, Moksnes and colleagues reported on a study of 40 patients 11.0±1.4 years of age with ACL injuries (80.5% nonoperative treated knees and 19.5% surgically treated). At the 3.8±1.4 year follow-up, only 28.5% of the 28 nonoperatively treated knees showed an increase in meniscal injury, as found in the follow-up magnetic resonance imaging. Only 3.6% of the nonoperative knees were found to have obtained new meniscal and cartilage injuries. They report the majority (88%) of the patients were physically active at the 3.8±1.4 year follow-up.11

Conversely, Vavken and Murray conducted a systematic review in 2011 on conservative versus operative treatment of ACL tears in the skeletally immature patient culminating in a review of 12 conservative treatment articles. They reviewed a total of 476 patients with an average follow-up time of 52.7±11.9 months and report multiple accounts of knee instability and meniscal and cartilage damage eventually requiring surgical intervention.12 One study reviewed found no increase in secondary injury rates between the operative and nonoperative treatment groups. These authors maintain that “absolute activity restriction is key” to avoiding further injury.13 Vavken and Murray conclude that conservative treatment should be reserved for compliant patients who have a low physical activity levels.

Because of concerns about physeal injury, some centers have implemented protocols to delay ACL surgical reconstruction until skeletally maturity. Moksnes et al14 demonstrated that use of ACL brace and rehab may allow the majority of skeletally immature to return to activities with a brace, with up to 65% returning to sports before ACL reconstruction after maturity. About 10% sustained secondary meniscus injury. Additional research by Moksnes et al15 showed immature athletes returned to activity, but at reduced levels in up to 38%. In 2014, Moksnes and colleagues reported on a prospective case series of 41 skeletally immature ACL injuries treated with nonoperative care. After an average follow-up at 3.8 years postinjury, 88% of the patients were participating in pivoting sports suggesting nonoperative treatment may be a viable option for some patients. However, 19.5% of the patients had sustained new meniscal injuries.11 Moksnes et al16 suggested that nonoperative treatment could be an option for the skeletally immature patients who do not present with major instability, and could allow the patient to postpone surgery until they have reached skeletal maturity. The main downside to this approach appears to be a significant risk of secondary meniscus injury for active children who delay ACL reconstruction.


This review shows that nonoperative treatment protocols may be considered reasonable for pediatric ACL ruptures for those patients who can comply with significant or complete activity restriction.17,18 For active patients, conservative treatment has been shown to result in secondary meniscal and cartilage injury and premature degeneration, even in the setting in which rehab training and brace wear are part of the treatment protocols.9,10,12,14,15,19–25 Recurrent episodes of knee instability are common for those who attempt to resume high level athletics without a reconstruction. Some surgeons chose a nonoperative treatment route such as physical therapy, bracing, and activity modification until the patient is skeletally mature. Physical therapy focused on muscle strengthening combined with bracing may improve the functional outcomes of those ACL deficient knee, but nonoperative measures were not often effective unless coupled with significant activity restriction.11,13,26


The ACL is a vital knee ligament providing stability and preventing secondary knee injury in active individuals. Knee instability, further meniscal/chondral damage, and an inability to resume sporting activity have been reported as consequences of delayed surgical treatment after ACL injury in young patients. For these reasons, surgical procedures may be recommended in active patients to restore functional knee stability, and to reduce the risk of secondary injury.


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anterior cruciate ligament; skeletally immature; natural treatment; knee instability; osteoarthritis

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