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Management of an Anterior Cruciate Ligament Tear in a 5 Year-Old Boy

Masaracchio, Michael PT, PhD, OCS, SCS, FAAOMPT; Comet, Sheryl PT, DPT; Godwin, Ellen PT, PhD, PCS

Author Information
doi: 10.1097/PEP.0000000000000154
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The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments in the body,1–4 with 2 000 000 ACL tears worldwide, annually.2–5 Children and adolescents in the United States account for 0.5% to 3% of these injuries.4 Usually, ACL tears result from sports-related activity, but may also result from non-sports-related traumatic events. Currently, no definitive algorithm is available to treat isolated ACL tears in patients who are skeletally immature.6 In addition, there is a paucity of research comparing early or delayed operative management with nonoperative management.7 Clinicians are therefore left to manage these injuries on the basis of clinical experience, low levels of evidence, and expert opinion.

The ACL is 1 of the 4 major ligaments supporting the knee. An intra-articular ligament, the ACL is located in the intercondylar notch between the femur and the tibia, running from the medial side of the lateral femoral condyle to the medial tibial spine.8,9 The ACL is approximately 18 mm in length and 11mm in width.10 Functionally, the ACL has 2 bundles: the posterior-lateral bundle, and the anterior-medial bundle. The posterior-lateral bundle is the most important component of the ACL, and the 1 that primarily becomes taut with knee extension.8,10 The ACL is well innervated with nerve and vascular supply, receiving innervation from the tibial nerve, a branch of the sciatic nerve, and blood supply from the middle geniculate artery, a branch of the femoral artery.9

The ACL prevents anterior tibial translation on the femur during open kinetic chain knee extension, and posterior femoral translation on the tibia during closed kinetic chain knee extension. The greatest strain on the ACL is during the last 30° of knee extension. Functionally, the ACL is primarily responsible for limiting sagittal plane motion, but also has a role in limiting extremes of varus, valgus, and rotation. Interruption of the fibers in the ACL often leads to instability in both the sagittal and transverse planes.8,10

ACL injuries include contact (traumatic injuries) and noncontact injuries. Most injuries are noncontact in nature.11 Several mechanisms of injury have been reported in the literature. These can include hyperextension of the knee, a valgus force, or a combination of these with a large internal rotation torque, thus causing external rotation of the femur on the tibia.11 Regardless of the mechanism, isolated ACL tears occur less than 50% of the time.12,13 Concomitant injuries may include bone bruises, meniscal tears, cartilage damage, and collateral ligament damage, as well as intra-articular fractures. Clinical decision-making algorithms in the presence of concomitant injuries can assist in the management of ACL tears.14

The current management for isolated ACL injuries includes both operative and nonoperative approaches. The literature suggests positive outcomes after ACL reconstructions in children who are skeletally immature, with all patients returning to their preinjury level of function with minimal complications.15–17 Although limited research is reported on ACL injuries in children younger than 10 years, 2 case studies detail successful management of ACL reconstruction in a 7- and an 8-year-old child.18,19 In both instances, the patients were able to return to sporting activities with minimal complications reported.19 Reports of long-term follow-up after ACL reconstruction in individuals who are skeletally immature are lacking, making it difficult to consider surgical management the reference standard.18

The risks and benefits of conservative versus operative management of ACL injuries in children with open growth plates have been discussed in the literature.20–22 Although surgical management often leads to increased stability of the knee joint, potential growth plate damage can be detrimental to the long-term functional capacity of the child. Authors of a recent case study18 advocated the continued use of the guidelines published by Kocher et al in 2002,23 which recommended conservative management of individuals 14 years or younger who sustained a partial ACL tear with near-normal Lachman and pivot shift tests. Physical therapy (PT) and/or bracing can offset the deleterious effects present after an isolated ACL injury in children with open growth plates. The purpose of our retrospective case study was to illustrate conservative clinical decision making in the management of a 5-year-old boy with an isolated mid-substance ACL tear in the absence of definitive treatment algorithms.


History of Present Injury

The patient, a 5 year-old boy, complained of left (L) knee pain after jumping off a chair, and landing with his knee in flexion, internal rotation, and abduction (valgus force) on June 29, 2013. The chair then landed on the posterior-lateral aspect of the patient's L knee, causing a valgus force, with probable anterior tibial translation. After the injury, the mother reported taking the child to the emergency department (ED) because of the child's inability to bear weight through the L lower extremity (LE). While in the ED, the patient was evaluated by an orthopedic resident who ruled out fractures of the tibia and femur. The patient was instructed to return in 3 days if he was still unable to bear weight symmetrically.

On July 2, 2013, the patient returned to the ED still complaining of pain when bearing weight. The same orthopedic resident who saw the patient initially performed an examination, which revealed a 3+ Lachman test. The resident ordered magnetic resonance imaging (MRI), which confirmed a mid-substance L ACL tear. He then provided education to the mother regarding rest and modified activity, and the patient was discharged home. The patient subsequently began PT approximately 6 weeks later on August 9, 2013, in a private PT practice.

Social History

The patient was living with his mother and began kindergarten in September 2013, 1 month after the initial PT examination. The mother reported that before his injury he was an active child who participated in a youth baseball team during the spring, enjoyed playtime throughout the day at school, and participated in yoga with his mother once a week.

Medical History

During the initial visit, the mother revealed the patient was born with a right (R) clubfoot, which required an Achilles lengthening procedure in 2008, followed by a posterior-medial capsule release in 2011. The mother stated no formal PT followed up these surgical procedures. However, the patient was instructed to wear a brace at night. Other pertinent medical history included a pyloric stenosis surgically corrected in 2008, bilateral hernia repair, and neonatal jaundice.


Pain scale ratings, strength assessment, and a variety of functional outcome assessment tools were used to determine progression and outcomes.

Numeric Pain Rating Scale

The Numeric Pain Rating Scale (NPRS) is an 11-point scale ranging from 0 to 10, with 0 representing no pain and 10 representing the worst pain imaginable. Patients rate the highest pain level over the last 24 hours. Previous research conducted on adults has shown the NPRS to be both reliable and valid, with a change of 2 points being clinically significant.24 The NPRS was chosen as an outcome measure because we believed the patient fully understood the scale and gave an appropriate number to his pain level, which seemed to correlate with the objective examination findings, and nonverbal communication. During the initial examination, the patient reported an NPRS of 4/10, which was located along the anterior aspect of the L knee.

Knee Injury and Osteoarthritis Outcome Score

The Knee Injury and Osteoarthritis Outcome Score (KOOS) is used to measure the patient's self-reported opinions about his/her knee function. This outcome measure is intended for young and middle-aged populations with posttraumatic osteoarthritis, along with injuries that may lead to posttraumatic osteoarthritis. We believed the activities addressed on the KOOS were representative of the child's activities before his injury and in addition believed this outcome measure was appropriate for this child because posttraumatic osteoarthritis can be a potential long term consequence after an ACL injury. The KOOS has 42 items divided into 5 domains. Each item is scored from 0 to 4. The raw score is totaled and converted to a percentage. Higher percentages correspond to greater knee function.25,26 The KOOS has been shown to be both a reliable and valid measure, with a minimal detectable change between 6 and 12 points for knee injuries. No report of a minimal clinically important difference for this measure was found in the literature.25,26 During the initial examination, the KOOS was administered through the patient's mother to improve the accuracy of the score. We recognize this reduces the validity of the measure, and therefore clinicians may want to view the results with caution. The patient's initial KOOS was 58/100.


Neurovascular Testing

Based on the history of congenital clubfoot, his reflexes, myotomes, and dermatomes were examined to assess the integrity of the nervous systems. No radicular symptoms or motor weakness associated with myotomal involvement, or sensory loss, were noted. Tibialis posterior and dorsalis pedis pulses were symmetrical.


During typical musculoskeletal development, children demonstrate genu varum from birth through 2 years of age, when knee alignment begins to move toward genu valgum, peaking at age 4 years. At this point, the child begins to develop neutral knee alignment.27 In standing the patient demonstrated a narrow base of support with R forefoot adductus in combination with R rear foot pronation. Neutral alignment of the L LE, and 1° of genu varum, was noted on the R LE. This alignment represents typical musculoskeletal development for a 5-year-old child.28 Muscle atrophy was observed in the R calf. Visible swelling was noted over the L mid-patella region.


General tenderness to palpation was found over the anterior aspect of the L knee. The sequencing of palpation in the clinical examination process is somewhat controversial. Many clinicians suggest placing palpation at the end of the examination process. This is commonly done because palpation can irritate tissues and subsequently yield questionable results during further clinical testing. We decided to perform palpation in the beginning of the examination to increase rapport with the patient because of his age and fear of pain.


Mid-patella circumferential measurement revealed a 1.5-cm difference in girth (L circumference 24 cm, and R circumference 22.5 cm). This difference may have been due to swelling; however, we recognize the difference could also be attributed to measurement error. In addition to circumferential measurements, the Stroke test29 has been developed to assess knee joint effusion. Beginning below the joint line on the medial aspect of the knee, a gentle upward stroke is applied to the level of the suprapatellar pouch and then down the lateral aspect of the patella. The clinician watches for a wave of fluid along the medial aspect of the patella. This test revealed a 1+ effusion of the patient's L knee. A recent study has demonstrated this test to be a reliable method for assessing knee joint effusion.30 Although this research was conducted on adults, we believe the physiological impairment of edema is similar in adults and children and therefore the Stroke test can still provide information regarding the degree of effusion.

Range of Motion

The patient's LE range of motion (ROM) was tested in the supine position, and was limited in L knee flexion during active and passive ROM testing because of pain (Table 1). Previous research has identified normative values for knee flexion and extension ROM in children between the ages of 1 and 5 years.31 These measures were performed in the same positions using the same landmarks used in the adult population. Intrarater reliability for knee passive ROM has been reported to be excellent for both flexion (intraclass correlation coefficient [ICC], 0.97-0.99) and extension (ICC, 0.91-0.97), respectively. Interrater reliability has been reported to be excellent (ICC, 0.91-0.99) for flexion and good (ICC, 0.64-0.71) for extension.32 Because previous research has identified normative values for knee ROM in children using identical landmarks as adults, we decided to implement the same testing procedures we would on an adult with an ACL tear.

Range of Motion at Initial Examination

Strength Testing

The patient's overall LE strength was found to be limited in the L hip and knee as well as the R ankle during manual muscle testing (MMT) (Table 2). The grades used in this case report (0-5) are based on Kendall's grading scale.33 A previous systematic review suggested that MMT is a clinically useful tool during the examination process. However, further research is needed to scientifically validate MMT results.34 Because the reliability of MMT grades has been called into question, we also performed handheld dynamometer (HHD) strength testing of the quadriceps because of its significance in the rehabilitation of individuals with ACL tears.5 Researchers recently concluded that the use of both MMT and handheld dynamometry was highly valuable in obtaining accurate information to guide clinical decision making.35

Muscle Strength at Initial Examination

When considering the reliability of MMT and HHD in children, the literature suggests MMT is a common method used for assessing strength in children, examining volitional activity of specific muscles throughout the ROM.33,36 However, the use of HHD provides a more precise level of measurement and is more sensitive to small changes in strength. In addition, HHD has been demonstrated to have better interrater reliability, test/retest reliability, and concurrent validity when compared with MMT.36,37 Previous research has documented the use of HHD to provide accurate and consistent readings in children as young as 2 years old.38 Therefore, we decided to assess strength using both standardized MMT grades and HHD to more objectively quantify and evaluate changes in strength over time. The results during the evaluation revealed an asymmetry in quadriceps strength, with the L quadriceps measuring 73% of the R quadriceps (L 8 lb, R 11 lb).

Joint Mobility Assessment

Accessory motion testing of the LE, performed to determine whether limitations in motion were due to capsular restrictions or the presence of pain and inflammation, revealed limitations in tibiofemoral and patellofemoral arthrokinematics of the L knee. As the injury occurred 6 weeks before the patient began PT, we concluded the limitation in mobility was due more to capsular restrictions than the inflammatory process, despite a Stroke test grade 1+ effusion. Our clinical decision was based on 2 factors. First, the child's unwillingness to maintain end-range position for over 1 month could potentially contribute to capsular restrictions. Second, an effusion of 1+ is mild and because the patient was only missing end-range motion, we theorized that the minimal effusion was not the primary impairment limiting mobility.

Positive Special Tests

Lachman Test

This test is designed to assess the integrity of the ACL. The patient is placed in the supine position and the knee is positioned in 30° of knee flexion while the tibia is anteriorly translated with respect to the femur.29,39 A positive test is defined as excessive anterior tibial translation without a firm end-point compared with the other side.39 The standard adult Lachman test was used yielding a 1+ rating, which is considered mildly positive, demonstrating 5 mm or less of anterior tibial translation. This was improved from the original Lachman test conducted by the orthopedic resident in the ED, where the rating was a 3+.40,41 The child subsequently had an MRI confirming the presence of a complete ACL tear. The Lachman test has demonstrated significant specificity and sensitivity, and is considered the reference standard in clinical practice.39 The diagnostic accuracy of the standard adult Lachman test in children has not been extensively studied. One prior study that specifically addressed the accuracy of the Lachman test in a pediatric population yielded similar diagnostic accuracy as currently reported for adults.42 The accuracy of the Lachman test must be considered within the overall presentation of the patient. The ability to accurately assess this ligament in the presence of effusion or hamstring spasm is less than optimal and can potentially lead to a false-negative result. Lachman testing in chronic cases of ACL insufficiency is usually more reliable in the absence of excessive hamstring spasm or joint effusion.40,41

Thomas Test

Designed to detect iliopsoas and/or rectus femoris shortness, the patient is positioned in the supine position with 1 knee pulled to the chest until the lumbar spine begins to flex. The tester then determines whether the thigh of the opposite leg maintains contact with the plinth. A positive test is observed when the thigh does not contact the plinth, thus indicating iliopsoas or rectus femoris muscle shortness.43 An increase in hip extension when the knee was passively extended revealed shortness of the L rectus femoris.

Functional Testing


The patient ambulated with decreased heel strike bilaterally, decreased L terminal knee extension during late swing phase, bilateral femoral internal rotation, and decreased pelvic rotation in the transverse plane throughout the gait cycle. Despite gait impairments, the child did not display a decreased cadence. However, the child demonstrated a slight asymmetry between R and L stance phases. Although the ACL tear was on the L, decreased stance time and stability were noted bilaterally, most likely because of his R congenital clubfoot. We concluded that the gait deviations were due to the limitations in ROM and strength, as well as the R congenital clubfoot.

Stair Negotiation

The patient used a step-to pattern to ascend and descend stairs. The child ascended the stairs leading with his R LE, and descended the stairs leading with his L LE. We believe this was most likely due to his fear of using his injured L leg, but could also result from poor eccentric quadriceps control. He used the handrail to ascend and descend stairs, and demonstrated poor eccentric control of the L quadriceps muscle when descending.

Balance Testing

During single-leg stance, the patient demonstrated an inability to maintain balance in a controlled fashion for greater than 5 seconds bilaterally. The test was conducted 3 times on each LE and an average computed. A recent study has illustrated that single-leg balance in 5-year-old children is at least 10 seconds.44 This correlates with the Peabody Developmental Motor Scales 2 scoring for a 60-month-old child, who receives a full score for a 10-second single-leg stance test.45 Below average scores were recorded during the initial examination.


Interventions throughout the course of PT consisted of manual therapy, therapeutic exercises, neuromuscular reeducation, patient education regarding the home exercise program (HEP), and precautions at home and school. Initially treatment focused mainly on manual interventions consisting of both soft tissue and joint mobilizations to address impairments identified during the examination. As the patient progressed, treatment focused more on therapeutic exercises and neuromuscular control activities (Table 3).

Progression of Interventions

Weeks 1 to 6

Interventions during the first 6 weeks were designed to achieve the following goals: decrease effusion, obtain symmetrical ROM and muscle length compared with the uninvolved side, increase muscle strength by 1 grade, and promote independence during the HEP. By achieving these goals and restoring preinjury objective measures, the patient was able to progress to more advanced functional activities representative of daily life (Table 3).

Weeks 6 to 12

Manual therapy interventions were discontinued, and the main goal of treatment shifted to increasing neuromuscular control and safety during functional activities. Interventions during this period focused on strength training during functional movement patterns, and the progression of balance training from stable to unstable surfaces, double-limb support to single-limb support, contact guard to supervision, and sagittal plane running to multidirectional cutting and pivoting. By achieving these goals and restoring neuromuscular control, balance, coordination and agility, the patient was able to return to unlimited gym and recreational activities without restrictions (Table 3).


After interventions, it is extremely important for clinicians to be able to assess the effectiveness of the treatment provided. It is not sufficient only to assess impairment level outcomes. Functional activities and standardized measures also need to be included to provide a thorough assessment. In this retrospective case report, the patient demonstrated improvement in the NPRS, the KOOS, knee ROM, hip and ankle strength, as well as dynamometer quadriceps strength, and single-leg stance time at discharge. These improvements provided the rationale for allowing the patient to safely return to unrestricted school and home activities (Table 4).

Baseline, Reevaluation, Discharge, and Follow-up Outcome Measures


Evidence-based rehabilitation protocols for the management of ACL injuries in young children are limited.18,19,21,46 Our management of this patient was unique from previous reports because surgical intervention was not considered, and protocols implemented in previous cases were those used for the adult population.5,18,19,46 Similar to our rehabilitation progression (Table 3), those protocols first focused on restoring ROM and strength, and then progressing to more dynamic functional activities to prepare children for unrestricted activity.

To the best of our knowledge, no previous literature exists on the nonoperative management of ACL tears in a 5-year-old child. Despite previous research suggesting the success of ACL reconstruction,15–17,47 this case report demonstrated successful outcomes with conservative management. Researchers have suggested that quadriceps strength of 85% or higher is sufficient to return to higher-impact activities.5,48 The therapist's decision to allow the patient to return to unrestricted physical activity was based on this criterion. As previous research was not focused on young children with ACL tears, our results need to be viewed with caution.

The KOOS increased beyond the minimal detectable change, suggesting increases in function exceeded measurement error. The NPRS demonstrated a complete reduction in pain from baseline to discharge. Although we believe the child understood the concept of this outcome measure and accurately interpreted his pain levels, the NPRS may have limitations in a pediatric population. Other scales such as Oucher's Pain Rating Scale are more commonly used in the pediatric population to capture accurate pain ratings.49

Single-leg stance on the L increased from 5 seconds to 90 seconds on discharge. Kakebeeke et al44 reported single-leg balance in 5-year-old children is at least 10 seconds. Combining these outcomes with reports of no pain, no instability (giving way episodes), and the ability to complete functional testing, we decided the patient was ready for discharge to an HEP.

The child in this report expressed interest in organized physical activities and demonstrated appropriate cognition and understanding to perform exercises appropriately and effectively. Therefore, we chose to implement a more standardized orthopedic approach. We believe children can benefit from this standardized orthopedic approach similarly to adolescents and adults. We believe children can perform structured exercise programs to aid in the restoration of quadriceps muscle strength and neuromuscular control, critical in the management of ACL injuries.5,50 The pediatric population may require less structured exercises to maintain compliance; however, we believe it is important to establish quadriceps control and strength before beginning play activities and sports-related drills. This is particularly true in a child this young, without surgical intervention, because adequate neuromuscular control is necessary to prevent future ACL or other ligamentous and cartilage-related injuries of the knee.5,50

Controversy currently exists regarding the best treatment options after ACL tears in children, as they are skeletally immature.21,22,51 Treatment options include conservative rehabilitation, traditional ACL reconstruction surgery, or ACL reconstruction surgery using a physeal-sparing technique.21,22,51 Although physeal-sparing techniques decrease the risk of growth plate disturbance, completely eliminating this risk is not guaranteed.21,22,51 Depending on the severity, the success of conservative management, and the activity level of the child, surgeons may successfully perform ACL reconstructions on open growth plates.15–17,47 The pediatric orthopedic surgeon had no intention of performing surgical reconstruction in this case, and opted for noninvasive conservative management using PT and bracing. This decision was guided by the potential for spontaneous healing of the ligament in this young child, coupled with the risks of operative management, and the medical and surgical history of the child.


First and foremost, cause-and-effect relationships cannot be established in case reports. However, the authors believe that rehabilitation after ACL injury is extremely important to counteract the potential long-term negative effects this injury poses on the musculoskeletal system. Second, the KOOS, although a valid outcome measure for adults, has not been validated in children, and as the mother completed the KOOS for the patient, the reliability and internal validity of the results are questionable. Third, although conservative management demonstrated positive changes in all outcome measures, possibly this injury favored a positive outcome because of spontaneous recovery of the ACL.

A unique aspect of this case was the fact that the child was born with a congenital R clubfoot. The etiology of this congenital defect was unknown.52 The child did not receive PT after Achilles tendon lengthening and posterior medial capsular release. He was given a brace, but adherence to brace use seemed questionable. Notable weakness in the patient's R LE was apparent, an inability to maintain single-leg stance on the R, and an overall decrease in R LE coordination. The patient coped with these impairments by placing more demand on his L LE. This coping strategy was compromised after the ACL injury to the L leg. The congenital clubfoot made it difficult to use the R leg as a basis for comparison for the L LE, and challenged the clinicians to vigorously assess improvements throughout the course of care. The rehabilitation plan accounted for the R congenital clubfoot, but the emphasis was on the L ACL injury because the L LE was the main focus for rehabilitation.

As with all interventions, adherence to the treatment plan is critical during any rehabilitation program. Throughout this treatment program, adherence to follow-up appointments with the orthopedic surgeon, punctuality with PT, and performing the HEP were inconsistent. Despite progress throughout the course of treatment in this retrospective case study, these inconsistencies may have contributed to less-than-optimal results. The entire health care team recognized this, and efforts to educate the patient and family about the importance of PT were attempted. With this inconsistency in following the treatment plan, we were not surprised that at the 3-month follow-up the patient demonstrated, except for the NPRS, a decline in all measures compared with discharge values, potentially because of poor adherence to the HEP.


This retrospective case report described the successful conservative management of a 5-year-old boy with a mid-substance ACL tear. To the best of the authors' knowledge, this represents the first case report on a child so young. Clinicians are encouraged to consider all variables present when choosing optimal interventions during the management of ACL injuries in patients with skeletal immaturity. We suggest a combination of playful activities along with standardized strengthening and neuromuscular control drills to optimize strength and motor control before a full return to unrestricted activity. The outcomes should be viewed with caution because this is a retrospective case report.


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anterior cruciate ligament/injuries; case management; case report; child; human; male; physical therapy

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