Background: Anterior cruciate ligament (ACL) tears are increasingly prevalent in the pediatric population. ACL rehabilitation is an essential component of recovery following injury and reconstruction, yet there are few explicit descriptions of pediatric-specific ACL rehabilitation protocols in the literature, especially in the context of varying treatment interventions. Our aim was to systematically review the literature on rehabilitation following ACL tears in children in order to describe common principles among different treatment options and areas of future research.
Methods: Using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we performed a systematic review of the PubMed, EMBASE, and Cochrane databases (for the past five years) to identify detailed rehabilitation protocols described in the pediatric population following ACL rupture. When available, the following aspects of rehabilitation were extracted: “prehabilitation” (exercises prior to surgery), bracing, weight-bearing status, range of motion, strength, modalities (ice, heat, electrical stimulation, etc.), plyometrics/proprioceptive exercises, return-to-sport criteria, and suggested ACL injury-prevention programs.
Results: Two hundred and two unique articles were identified. Twenty-seven articles meeting inclusion criteria with extractible rehabilitation data were included. A table, categorized by differing orthopaedic intervention, was designed to detail the components and duration of the different aspects of rehabilitation. While there are substantial differences across protocols, several trends emerged, particularly regarding weight-bearing, bracing, range of motion, and strength training. Interestingly, we found that many current protocols are based on time frame alone rather than on functional milestones; of the fourteen unique articles that addressed return-to-sport criteria by specific orthopaedic intervention, seven were based on temporal progression whereas seven also involved achievement of physical milestones. In addition, only three of the eight articles that mentioned a future ACL injury-prevention plan described a formal prevention program.
Conclusion: We systematically identified, and subsequently outlined and compared, the current trends of the various components of pediatric-specific ACL rehabilitation protocols, categorized by orthopaedic intervention. Several protocols are based on time frames rather than milestones achieved, with newer protocols involving milestone-based progression. Newer protocols are also incorporating formal prevention programs. Just as skeletally immature patients require unique methods of operative fixation, so too do they require catered rehabilitation protocols. To effectively prevent re-rupture or contralateral injury, future research should focus on prospectively evaluating each component of the rehabilitation protocols described and return-to-sport criteria for young patients.
Recent trends in sports participation demonstrate a continually increasing number of childhood athletes1,2. Improved injury recognition3,4, coupled with increases in overall participation, early sport specialization, the level of competition, and year-round high-intensity training, has led to a commensurate increase in the treatment of sports-related injuries5-7. With knee injuries accounting for approximately 50% to 60% of high school sports-related surgical procedures8,9 and the anterior cruciate ligament (ACL) accounting for >25% of all knee injuries10, the rate of ACL reconstruction in the United States continues to rise11,12. Overall, ACL injury rates vary by sport, sex, level of competition, and exposure type, with a reported injury rate among high school athletes of between six and seven injuries per 100,000 athlete-exposures1,13.
Multiple factors explain the increased risk of sports-related injury in young athletes, including growth-plate vulnerability, discrepancies between biological and chronological age, the adolescent growth spurt, and differential growth14. Younger athletes also have underdeveloped coordination, skills, and perception15. The most common mechanism of ACL injury is either a noncontact pivoting motion (valgus stress) with the knee partially flexed and the foot planted or trauma to a hyperextended knee16. The Lachman, anterior drawer, and pivot-shift tests are all highly valuable clinical tools to aid in the diagnosis; of these, the Lachman test is the most sensitive5.
Historically, concern about iatrogenic physeal injury and subsequent limb-length and angular deformities has limited ACL reconstruction in skeletally immature patients4,17. However, this paradigm has shifted, with instability, activity limitations, poor functional status, and increasing risk of irreparable meniscal and articular cartilage injuries having been noted in association with delayed reconstruction and nonoperative management18-26. Many new physeal-respecting techniques are able to minimize risk of physeal damage27, including the extraphyseal28, all-epiphyseal29, and all-inside all-epiphyseal approaches4. Furthermore, transphyseal reconstructions30 performed with use of central, smaller tunnels without hardware crossing the physis have been shown to be safe as well31-33.
Just as skeletally immature patients require unique methods of operative reconstruction, so too do they require distinct rehabilitation protocols because of variations in fixation methods, age, and patient maturity level4,34. Furthermore, younger patients are more active than adults35-37 and have a higher risk of reinjuring the ACL3,38. Nevertheless, few reports have explicitly detailed rehabilitation programs designed specifically for skeletally immature patients, especially in the context of varying treatment interventions. In the present review, we describe the results of a systematic review of the literature for rehabilitation following ACL ligament tears in children in order to outline common principles. The goals of the present study are to provide an accessible resource to orthopaedic surgeons and physical therapists and to identify areas for further research and improvement.
Materials and Methods
Using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines39, two reviewers (J.L.Y. and A.G.) independently carried out a comprehensive search of the PubMed, EMBASE, and Cochrane computerized databases for meta-analyses, randomized controlled studies, prospective cohort studies, retrospective case-control and cohort studies, case reports, and review articles; the last search date was October 3, 2014.
The following search terms were used: (ACL OR “anterior_cruciate_ligament”) AND (pediatric OR child*OR preadolescent OR juvenile OR “skeletally_immature”) AND (rehab*OR management). Articles were limited to human studies, written in English, that were published within five years before the search date. A secondary search was conducted by reviewing the bibliographies of included articles.
Following the primary electronic search, two reviewers (J.L.Y. and A.G.) independently conducted a title search for articles that potentially contained relevant information. If either reviewer deemed the title eligible, the manuscript was included in the review (1) if the study involved a pediatric patient population (with the patients being less than eighteen years old) and (2) if the ACL tear rehabilitation protocol was directly mentioned. The article was excluded if (1) the full article was not available in the English language, (2) the full article was not available online, or (3) the article had been published more than five years before the search date (Fig. 1).
Two hundred and two unique manuscripts were identified. The title search excluded ninety-nine studies, and the full text review excluded an additional seventy-eight articles (Fig. 1). One article was excluded because of the specific use of adult rehabilitation guidelines. The secondary search revealed two additional articles to be included, leaving twenty-seven in the final analysis.
Two authors (J.L.Y. and A.G.) collected data from each study, including general information (author and publication year), patient age, type of study, and all elements of the rehabilitation protocol. Table I displays a full list of included articles and the interventions discussed.
When available, the following aspects of rehabilitation were extracted: “prehabilitation” (exercises conducted prior to surgery), bracing, weight-bearing restrictions, range-of-motion restrictions, modalities (including ice, heat, electrical stimulation, etc.), strength, plyometrics and proprioceptive exercises, return-to-sport criteria, and ACL injury-prevention programs (Table II).
The twenty-seven analyzed articles (one Level-II article, two Level-III articles, twelve Level-IV articles, three Level-V articles, and nine review articles) were organized into nonoperative and postoperative rehabilitation protocols. The operative category was divided into transphyseal, partial transphyseal, intra-articular and extra-articular extraphyseal (e.g., iliotibial band), and all-epiphyseal protocols. Our aim was to systematically compare current rehabilitation protocols among the various treatment interventions.
Importantly, none of the included articles were designed to primarily evaluate rehabilitation protocols. Rather, they described the authors’ preferred rehabilitation protocol following ACL intrasubstance rupture. Three articles solely addressed nonoperative treatment, ten discussed transphyseal ACL reconstruction, four addressed all-epiphyseal ACL reconstruction, one discussed extraphyseal ACL reconstruction, one addressed a partial transphyseal approach, and the remaining eight addressed more than one intervention.
Eight articles addressed rehabilitation following nonoperative management7,40-46. Despite literature describing the merits of operative intervention in the skeletally immature patient population, operative intervention may not always be necessary (e.g., the patient may have no desire to return to competitive cutting and pivoting sports)40.
Two of the eight articles described rehabilitation guidelines according to the post-injury time frame, including early bracing, range-of-motion limitations and progression, weight-bearing status (toe-touch weight-bearing for the first eight weeks41 or partial weight-bearing guided by pain42), and a strength-training regimen including closed-chain and proprioceptive exercises, ultimately suggesting a slow return to sports three to six months after the injury with bracing41,42. The guidelines and return-to-sport criteria in the two articles are further detailed in Table II. The protocol described by Ziebarth et al. permitted contact sports six months following the injury and encouraged indefinite bracing during all sports activity following complete rehabilitation42. The protocol described by Streich et al. recommended informing patients of secondary intra-articular risk and regular follow-up surveillance41.
In one study, the nonoperative rehabilitation protocol was divided into four phases that were separated by physical therapy milestones rather than following a specific time frame43. The detailed protocol is outlined in Table III. Three other articles40,44,45 provided rehabilitation suggestions without describing a specific protocol. Activity limitation and functional bracing44 were encouraged, with a focus on active physical therapy emphasizing quadriceps strengthening40,44, neuromuscular rehabilitation40, and jump-landing44. Prior to return to sport, the protocol described by Moksnes et al. requires functional testing and offers a subsequent injury-prevention protocol consisting of neuromuscular and functional muscle-strengthening exercises following formal physiotherapy45.
Although partial ACL tears occasionally may be treated nonoperatively47, specific rehabilitation protocols for this patient population are not thoroughly described in the literature. The two articles that addressed this recommended activity modification, proprioceptive and neuromuscular physical therapy46, and possible bracing7,46. Frank and Gambacorta recommended return to sport within three to six months after the return of clinical knee stability7.
Ten articles were limited to the transphyseal approach in the pediatric population32,48-56. One article was strictly limited to patients with closed physes, so data were not extracted48. Five additional articles discussed transphyseal ACL reconstruction rehabilitation protocols in the broader context of pediatric ACL treatment7,41,43,46,57. The guidelines and return-to-sport criteria are detailed in Table II.
Eight articles discussed postoperative bracing, with the majority suggesting the use of a hinged knee brace for six weeks postoperatively7,41,49,50,57 and the others suggesting bracing for eight weeks51, for twelve weeks52, and for four weeks with restriction of motion between 0° and 90°53. Courvoisier et al. uniquely advocated postoperative long-leg casting54.
Eleven articles addressed postoperative weight-bearing. Five recommended touch-down or toe-touch weight-bearing postoperatively for two weeks7,54,57, for four weeks41, or until quadriceps function had fully returned52. Four studies described immediate weight-bearing as tolerated postoperatively32,50,51,55. Nikolaou et al. restricted patients to non-weight-bearing for three weeks followed by partial weight-bearing for two weeks53, and Mall and Paletta utilized a nonspecific “progressive weight-bearing” protocol46.
Six articles encouraged immediate or early progression of passive range of motion following surgery46,49,51,52,55,56, with three articles recommending the use of a continuous passive motion device49,51,57. Three articles recommended limiting range of motion to 0° to 90° for two weeks57 or four weeks41,53, with no restrictions thereafter. Another article suggested “motion limits” for the first two weeks or until the patient could perform twenty straight-leg raises without extensor lag50. One article encouraged increasing range of motion within the first three months postoperatively7, and another article suggested the goal of full knee extension by two weeks postoperatively32. Two articles encouraged early patellar mobilization7,50.
Nine articles discussed strength training, with two articles endorsing “progressive muscle strengthening exercises”46,52 and the remainder endorsing closed-chain exercises7,32,41,50,51,55,56. Three articles emphasized quadriceps and hamstring strengthening in the initial three months following surgery alongside modalities such as electric stimulation7,50,51. Hui et al.32 and Redler et al.50 further encouraged proprioceptive training during this early time period.
Plyometrics and straight-line jogging are allowed by approximately three months after surgery7,50, with some studies permitting cycling and swimming as early as eight weeks postoperatively and running by sixteen weeks postoperatively41.
Several articles discussed return-to-sport time frames and measures or programs designed to prevent repeat or contralateral injury. Five articles endorsed full return to sport at six months following reconstruction7,50,52,53,57, with an additional two suggesting the avoidance of sports involving cutting and/or pivoting until nine months51 or twelve months41 postoperatively. Two studies involved the use of hop tests or “sport tests” to determine when the patient can fully return to play, usually ranging from six to twelve months32,56. Four articles recommended the use of a functional ACL brace for one to two years postoperatively7,41,50,57, and one article suggested an ACL injury-prevention program56.
Finally, Moksnes et al.43 outlined four important differences between adult and pediatric rehabilitation protocols, describing slower progression to running and jumping to reduce physeal strain, less use of external loads during strength rehabilitation, an emphasis on home-based exercise, and a later return to sports in the pediatric population as compared with the adult population.
Physeal Sparing Techniques: All-Epiphyseal and Intra/Extra-Articular Extraphyseal
Two articles that addressed the transphyseal approach noted differences in the rehabilitation protocol following extraphyseal ACL reconstruction with use of the iliotibial band modified MacIntosh technique28. Both Frank and Gambacorta7 and Nwachukwu et al.57 described the use of bracing for six weeks postoperatively, with the patient being restricted to toe-touch weight-bearing. Nwachukwu et al. also limited range of motion from 0° to 90° for this period. Frank and Gambacorta7 encouraged patellar mobilization and closed-chain quadriceps and hamstring exercises within the first three months before progression to straight-line jogging and plyometrics. Both groups of authors recommended full return to sports at six months and the use of a functional ACL brace for one to two years. Although a third article on a unique physeal sparing technique provided fewer details, it described a forty-five-day period of casting in a long-leg cast in 10° of flexion followed by a forty-five-day period of rehabilitation involving a home exercise program58.
Four articles, including two from The Children’s Hospital of Philadelphia (CHOP)59,60 and two from the Hospital for Special Surgery (HSS)4,61, discussed rehabilitation following an all-epiphyseal ACL reconstruction.
In one of the studies from CHOP, Greenberg et al.60 described a brief “prehabilitation” protocol consisting of gait training, the assessment of maturity level and motivation, and substantial education of both the patient and family (addressing toe-touch weight-bearing precautions, pain management, techniques to reduce swelling, and an early exercise regimen). The authors described preoperative goals addressing range of motion, strength, effusion, and education (Table II).
Investigators from both HSS and CHOP have described detailed rehabilitation regimens involving the use of a hinged knee brace locked in full extension (Table II). In the CHOP protocol, the brace is unlocked at four weeks and brace use is discontinued at six weeks after the patient has met specific range-of-motion and strength requirements60. The CHOP protocol supports weight-bearing as tolerated with crutches beginning at two weeks, and the HSS protocol endorses partial weight-bearing through the end of the fourth week. Both the CHOP and the HSS protocols encourage the use of a continuous passive motion device for range of motion. The goals and time frames associated with the CHOP protocol are described below, in the section on the senior author’s preferred method. The HSS protocol strives for 90° and 125° of flexion by the end of the fourth and eighth weeks, respectively, while also emphasizing patellar mobility. The CHOP protocol specifies the use of electrical stimulation for quadriceps activation within the first week59, and the HSS protocol emphasizes immediate cryotherapy along with the potential use of an underwater treadmill after wound-healing if a patient is apprehensive about weight-bearing4.
Both the HSS and the CHOP rehabilitation protocols detail week-by-week strength goals and offer specific exercises as detailed in Table II and in the section below on the senior author’s preferred method. In addition, both protocols emphasize a home exercise program and specify criteria that are required to advance through to the sequential stages of rehabilitation. Finally, these institutions both have stringent return-to-sport criteria (Table II). Furthermore, the HSS protocol involves an ACL injury-prevention assessment during the sixteenth through twentieth weeks and evaluates for compliance with functional bracing after twenty-eight weeks61.
Partial Transphyseal Approach
Only one article specifically described a rehabilitation protocol for the partial transphyseal approach, which involves avoiding the physis of the distal part of the femur while traversing the physis of the tibia62. Of note, that report described a new technique involving the use of a single hamstring graft. For the first four weeks following surgery, patients who were less than twelve years old were managed with immobilization with the knee in extension in a long-leg resin cast whereas those who were more than twelve years old were managed with splinting in extension. During this four-week postoperative period, patients were restricted from weight-bearing and physiotherapy. No further rehabilitation protocol was described.
Three articles did not specify the operative technique used but provided guidelines regarding postoperative rehabilitation in youth athletes44,63,64. Albright and Crepeau64 discussed the “prehabilitation” goals of achieving good range of motion, resolution of acute inflammation, and early quadriceps activation and strengthening and suggested perturbation training prior to surgery.
With regard to range of motion, emphasis is placed on quickly regaining full knee extension within the first one to two weeks and patellar mobilization within the first few months to allow for progressive flexion44,63,64. Albright and Crepeau64 recommended 0° to 90° of flexion by two to four weeks, 0° to 120° by six weeks, and 0° to 135° by eight weeks. Schub and Saluan44 encouraged immediate use of continuous passive motion. No specific recommendations were made regarding postoperative bracing and weight-bearing.
Recommendations were made regarding early quadriceps activation and strengthening along with hamstring, hip, and core strengthening in the first few weeks postoperatively, with specific emphasis on straight-leg raises and active knee extension. Closed-chain exercises begin around five to six weeks and later progress to open-chain exercises. Within the first few months postoperatively, proprioceptive exercises, including perturbation, balance, and endurance training, should be emphasized63,64. LaBella et al.63 endorsed straight-line jogging, plyometrics, and sport-specific exercises beginning after the fourth to sixth postoperative months.
LaBella et al.63 described return to sport at around seven to nine months, whereas Albright and Crepeau64 offered performance-based guidelines, including >80% to 85% isokinetic quadriceps strength and >70% to 75% hamstring strength as compared with the contralateral limb, functional testing (including single-leg hop and triple jump), and successful progression through the rehabilitation protocol. Schub and Saluan44 recommended functional bracing for twisting, cutting, and pivoting sports, whereas Albright and Crepeau64 noted that no literature supports functional bracing in the pediatric population.
Considering Meniscal Involvement
When ACL injuries require concomitant meniscal repair, the rehabilitation protocol often is adjusted, specifically with regard to postoperative weight-bearing and range of motion. Nwachukwu et al.57 modified their rehabilitation protocol after transphyseal reconstruction with “restricted” range or motion and toe-touch weight-bearing for two to six weeks (as opposed to only two weeks) postoperatively, depending on the severity of the tear. Akinleye et al.59 modified the all-epiphyseal rehabilitation protocol by keeping patients partial weight-bearing and restricting range of motion from 0° to 90° until after four weeks postoperatively. In addition, in their protocol, isolated hamstring strengthening and squats below 60° are avoided until after the sixth week. Finally, McCarthy et al.4 and Fabricant et al.65 endorsed protected weight-bearing in the setting of meniscal repair and/or cartilage-restoration procedures. Conversely, restricted weight-bearing typically is not prescribed in the case of partial meniscectomy.
Rehabilitation after ACL injury and ACL reconstruction is an important aspect of the continuum of care ensuring that a young athlete will make a complete and safe return to his or her desired activity. In the present review, we have systematically identified and subsequently described current and various components of pediatric-specific ACL-rehabilitation protocols, categorized according to orthopaedic intervention. Several trends emerge among the different protocols, particularly regarding weight-bearing and range-of-motion restrictions, bracing (ranging from four to twelve weeks, with a majority of articles advocating six weeks), and strength-training progression (with a heavy emphasis on earlier closed-chain lower-extremity exercises progressing through open-chain activity); specific differences among orthopaedic interventions are detailed in Table II. In addition, many rehabilitation protocols are based on time progression, whereas more contemporary protocols are based on functional milestones32,42,43,48,56,60,61,64. Of the fourteen unique articles that addressed return-to-sport criteria according to specific intervention, seven (50%) were based on temporal progression7,41,50-53,57 whereas seven (50%) also involved the achievement of physical milestones32,42,43,48,56,60,61. Few have also implemented ACL injury-prevention plans7,41-43,50,56,57,61. Only three (37.5%) of the eight articles that mentioned a prevention plan described a formal prevention program. Despite the impact of rehabilitation on treatment success, explicit descriptions of rehabilitation protocols and objective functional outcome measures in youth athletes are currently limited43,66. With several ACL reconstruction techniques described for the skeletally immature individual, future research to develop evidence-based protocols tailored by procedure would ensure consistent success postoperatively.
Physiological and psychological factors specific to preadolescents may impact recovery after ACL reconstruction and thus limit the application of adult studies to this specialized population34. For example, while several studies have demonstrated the limited benefit of postoperative bracing and continuous passive motion in the adult population67, behavioral and emotional maturity differences may increase the importance of these modalities in children. Differences in attention span and information retention in this population must be kept in mind in general. In addition, exercise progression and training strategies may warrant a different approach in the preadolescent athlete because of differences in the mechanisms of strength gains and neuromuscular adaptation68,69. Neuromuscular control is of particular importance in this population, with many systematic reviews and meta-analyses having supported a role for neuromuscular training programs in preventing future ACL injury70-73. Moreover, preventative neuromuscular training has been shown to be cost-effective, and some have advocated for universal implementation of such training for the management of youth athletes74.
Current trends in ACL reconstruction rehabilitation in children emphasize a combination of time and performance-based criteria to assist with activity progression75,76. In particular, the postoperative periods of protected weight-bearing, activity advancement, and return to sports are often longer for children as compared with adults. The recommendation for prolonged activity progression stems from concern for extended strength and functional performance recovery times and out of respect for youth immaturity and behavioral challenges34,60. A recent retrospective study demonstrated delayed strength recovery following ACL reconstruction when preadolescent athletes were compared with adults34. This finding supports prolonged rehabilitation requirements; however, additional research is needed to derive improved guidelines for rehabilitation time frames and protocol advancement.
Currently, the majority of published studies have relied on patient-reported outcome scales, such as the International Knee Documentation Committee scale, the Tegner activity scale, or the Lysholm score, to judge successful return to activity77,78. Although useful, these scales do not provide the rehabilitation professional with documented physical performance criteria in order to judge the ability of a young athlete to handle the rigors of return to full sports activity and they are not validated for the evaluation of children. Going forward, researchers should employ pediatric and adolescent-specific scales35,79. Some protocols have suggested using the criteria of 85% to 90% limb symmetry on a group of standardized single-leg hop-tests as objective outcome measures for return to sports60,61, whereas others have suggested using an assessment of quadriceps peak torque symmetry59,64. Although these tests are widely used within the adult population, they are not validated for the evaluation of youth athletes. Experts recently have voiced concern that our current methods of judging full performance recovery after ACL reconstruction are inadequate and may be contributing to the occurrence of re-rupture or contralateral limb injury on return to activity80. Lentz et al. examined differences in a variety of clinical variables and an athlete’s return to pre-ACL injury function and discovered specific variables that were tightly associated with return-to-sport status, including joint effusion, episodes of instability, and patient-reported knee function81. The replication of a similar study in the pediatric population could help to answer several questions and establish more specified guidelines for return to sport.
We recognize that the present study has limitations, including restricting the included studies to the English language, the inclusion of studies with varying levels of evidence, and limiting the study period to five years. We recognize that children were at risk for ACL injury long before 2009; however, as reconstructive techniques are evolving rapidly, several currently used surgical procedures did not exist several years ago. We also recognize that heterogeneity in surgical procedures, rehabilitation protocols, and outcome measures preclude meta-analysis; none of the included studies specifically examined the outcomes of rehabilitation in terms of the retear or reinjury rate. The present study was therefore not intended to be a comparative outcomes paper, but rather an up-to-date overview and resource for orthopaedic surgeons and physical therapists who treat ACL ruptures in pediatric patients. Future research employing validated outcome data following rehabilitation protocols is needed.
ACL tears are becoming increasingly prevalent in the pediatric patient population. While innovative surgical interventions continue to be developed, it is imperative for each patient to undergo adequate rehabilitation prior to returning to sport in an effort to both return to preoperative functional ability while preventing a repeat tear or contralateral injury. Currently, few youth-specific rehabilitation protocols have been described, and many have been designed on the basis of a combination of the adult literature and clinical expertise. Many are based on time frames rather than milestones achieved. Additional studies should be conducted to prospectively evaluate rehabilitation protocols and return-to-sport criteria for young athletes while keeping in mind both physical and psychosocial differences between children and adults.
Senior Author’s Preferred Rehabilitation Protocol: All-Epiphyseal ACL Reconstruction
Protocol modifications for concomitant meniscal repair are described in Table II.
Patients are maintained with toe-touch weight-bearing for two weeks postoperatively7,57,60. Continuous passive motion is prescribed for six hours per day, beginning from 0° to 30° and increasing 5° to 10° per day as tolerated4,49,51,57,59. When the patient is not performing range-of-motion exercises, the knee is immobilized in a hinged knee brace in full extension to protect the reconstruction during transfers and to minimize the risk of a knee flexion contracture4,60. Isometric quadriceps-activation exercises (i.e., quad sets) are started immediately82. Compression, cryotherapy, and elevation strategies are used to minimize pain, edema, and effusion4,59.
Formal physical therapy begins on the fifth to seventh postoperative day. More advanced knee flexion range-of-motion exercises are added to the program (Fig. 2), along with hamstring/calf stretches to ensure that the patient maintains full knee extension. Range-of-motion milestones include 0° to 90° by the end of the second week postoperatively57,60, 0° to 120° by the end of the fourth week, and full range of motion by the sixth to eighth week. Neuromuscular electrical stimulation (Fig. 3) and alternate exercises are utilized to improve quadriceps contraction (Video 1, Video 2, Video 3)7,50,51,59. Therapeutic exercises are advanced, with primary focus on closed-chain functional exercises targeting the knee, hip, and core (Fig. 4, Video 4, Video 5, Video 6, and Video 7). Although weight-bearing as tolerated without a brace is permitted during therapy, walking status at home continues to be restricted for several weeks to minimize impulsive activities that risk reinjury.
Walking is progressed to weight-bearing as tolerated with the brace locked in extension after the second week. If the patient demonstrates adequate knee control, the brace may be unlocked during the fourth week. Use of the brace can be discontinued during the sixth postoperative week if the patient meets specific criteria, including a knee range of motion 0° to 100° and the performance of a single-leg squat from 0° to 30° with adequate knee control. Exercises such as cone walking (Video 8 and Video 9) and mirror-feedback motor-control activities are utilized to help restore normal gait.
During the sixth to sixteenth postoperative weeks, exercises progress to higher-demand activities that increase strength requirements (Video 10), balance demands, and functional limb control68-73. Examples include progressing from double-limb to single-limb closed-chain activities (double-leg to single-leg squat [Video 4 and Video 11]), moving from uniplanar to multiplanar functional exercises (forward lunge [Video 12] to multi-angle lunges or star activity [Fig. 5]) and progressing from controlled to more dynamic surfaces (e.g., ground to BOSU ball).
Advancement to running and double-leg jumping is allowed at the sixteenth week if the specific criteria are met, including a limb symmetry index (LSI) of 75% or better in peak torque quadriceps strength82, full knee range of motion, no effusion, and toleration of all activity progressions. Jogging progression begins with walk/run intervals of 0.1 mi (0.16 km) each. The volume and distance of running are tailored to the individual patient on the basis of the previous level of physical function. Progression of plyometric exercises similarly advances from double to single-leg and more dynamic/multiplanar jumping as power and control improve (Video 13, Video 14, and Video 15). Progression of sports-specific training typically occurs through the sixth through ninth months if specific requirements, including an LSI of 90% in peak torque quadriceps strength82 and a series of single-leg hop-tests with appropriate quality of movement (i.e., adequate knee flexion during landings, no dynamic knee valgus during takeoff or landings, no loss of trunk or pelvic control during activity). During the return-to-sports integration period (six to twelve months), emphasis is placed on restoring cardiovascular endurance, anaerobic training, sports-specific agility and coordination, ongoing plyometric exercises, and a long-term structured lower-extremity injury-prevention program.
Physician clearance for full return to unrestricted activity is based on successful completion of the above protocol and occurs no earlier than nine months postoperatively, and typically at twelve months postoperatively, in order to prevent repeat injury82,83. A functional ACL brace is recommended for most patients prior to return to full activity7,41,50,57,61. For multisport athletes, focus on a single sport is recommended for the first season (minimum) on returning to full activity.
Source of Funding: No external funding source was provided for this study.
Investigation performed at The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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