Early management or phase one of rehabilitation of an ACL injury in a pediatric patient should focus on addressing acute hemarthrosis or effusion, regaining normal range of motion, and initiating reactivation of the quadriceps. Phase one should begin with guidance from a physician and evaluation of an MRI confirmation and specifying the location of the ACL injury and the absence of associated injuries (including a bucket handle meniscus tear, an osteochondral fracture, or a multi-ligamentous knee injury) [53]. A modified protocol may be required with concomitant injuries.

Protected weight bearing is recommended for the first 3–4 weeks, with a range of motion brace without motion restrictions [1, 29, 44, 51]. If limited weight bearing is desired due to the presence of an osteochondral contusion, this may be employed. Although toe-touch weight bearing is acceptable at this stage, a pediatric patient may have difficulty with understanding and appropriate compliance. Developing trust is important in this early stage to ward off inappropriate weight bearing on crutches. Crutch training could prevent patients from leaning on crutches as it can compress the nerve and blood vessels in the armpit. Cryotherapy and compression should be considered to manage any effusion, since this may limit a patient’s recovery.

Flexion and extension exercises are employed without the brace, with severity of the effusion often dictating how fast each patient progresses. The introduction of modalities and anti-inflammatory techniques may be indicated at this time. Therapeutic techniques with anti-inflammatory effects may include electrical stimulation, ice, warm pad modalities, or ultrasound. Early motion recovery is achieved with focused rehabilitation on both flexion and extension. Achieving terminal extension is of paramount importance to reaching pain-free activities of daily living and more advanced functional goals. The focused extension program is initiated supine with an ankle foam roller (Fig. 8.1a). When pain and effusion are minimized, prone knee hangs (Fig. 8.1b) are implemented without weights, with subsequent progression to weighted prone knee hangs by adding a 3-pound cuff weight distally. For flexion motion and early quadriceps eccentric contraction, wall slides and straight leg raises are also initiated (Fig. 8.1c, d). Initially, straight leg raise is performed in a supine position with the patient’s head supported with elbows propped up in order to visualize the extremity during the exercise. Eyes are instructed to focus on the knee for visual feedback to prevent terminal knee extension lag. Initially, the contralateral knee is flexed to provide support and then progressed to extended once the patient is able to perform a straight leg raise without an extension lag. Following this, sitting straight leg raises are initiated. A stationary bike without resistance for 20 min per day can be implemented during this phase. Once the patient demonstrates knee flexion to 100°, adjust the bike seat height to allow slight knee flexion on downstroke and properly position patient to prevent valgus knee alignment during pedaling stroke. Early quadriceps activation may be improved with supine single leg press using elastic band to 20 (Fig. 8.2a).

Milestones for phase one include complete resolution of effusion, a straight leg raise without a lag, and full unrestricted motion. Completion of these milestones will allow progression to phase two no sooner than 1 week following the initial injury. Underwater or devices that reduce the effects of gravity provide an environment that allows the treating physical therapist to cue, train, and guide the client to develop a normal gait pattern. Utilizing these unloading modalities improves confidence and reduces joint pain.

Phase two should be considered and completed for all patients prior to surgical decision-making. The primary goal of this phase is to normalize activities of daily living (ADLs) by restoring muscle strength and early neuromuscular response [49]. This is accomplished with muscle strength training, plyometrics, and neuromuscular exercises. Early phase two programs may be initiated without weight-bearing activities. Strengthening quadriceps and hamstrings with closed chain exercises is started [1, 29, 50]. Progression of the supine single leg press with an increase in repetitions prior to an increase in resistance is recommended. Emphasis is placed on developing hamstring strength due to its role as a dynamic muscular backup to an AC-deficient knee. Recent evidence has supported the importance of gluteus medius and hip external rotators strengthening in prevention of future ACL injuries [50, 54]. Gluteus medius strengthening is accomplished with a lateral decubitus clamshell exercise (Fig. 8.2b). By instructing the patient to put their hand on the iliac crest, they will minimize rotation during this exercise.

When weight-bearing restrictions are removed, early neuromuscular control is progressed with terminal knee extension in single-leg stance: a mirror for visual feedback and assistance for balance may be useful (Fig. 8.2c, d) [50]. A narrow stance with an elastic band (TheraBand, Akron, OH) around the distal thigh for a single-leg hip external rotation exercise will activate hip rotators. Progressing to a shoulder-width squat will add difficulty. Attention is directed to correct a compensatory weight shift that may develop away from the affected lower leg. It is important to clear the joint above and below the knee for full active range of motion. For instance a loss of ankle dorsiflexion will cause a squat dysfunction.

A stationary bike and a swimming program may be emphasized here. Swimming programs are effective initially with a floatation device that allows for walking, such as a kickboard. Frog kicks should be avoided (i.e., kick used in breaststroke). Proprioception and balance training are initiated with single-leg stance, step-ups, and squatting that avoid dynamic valgus loading [12, 31]. Proximal hip strength is an important consideration during this phase.

A repeat examination by a trained healthcare professional should be performed prior to progressing to phase three in order to confirm no mechanical symptoms or effusion. In order to advance to phase three, the young patient should be able to complete normal stair walking and participate in daily activities. Any history of instability, activity-related pain, or signs of a residual effusion should be addressed by a physician.

Initiation of phase three is intended for those young athletes who are considering nonoperative management of an ACL injury [44]. Moksnes [50] stated that the primary goal of phase three is the ability to run without gait deviation or swelling. The athlete should be able to complete one-mile jog without fear or instability, and, if able to complete, progress to single-leg linear skipping and low-amplitude base hops to single-leg hop. The progression of phase three is primarily determined by the physical therapist.

An emphasis on neuromuscular control, balance, and proprioception is placed during the early stage of phase three. Simple balance routines with uneven surface training using equipment such as a wobble board, Bosu^® balance trainer (Bosu, Ashland, Ohio), or an Airex^® balance pad (AIREX, Switzerland) will aid in building neuromuscular control prior to single jumps and multi-hop plyometric movements. An Airex^® balance pad with a slight knee flexion stance and perturbation with an elastic band will supplement the neuromuscular training. To be performed properly, the young patient will need to be upright with short arc of motion and shoulder in extension (see Fig. 8.3a).

Proper landing techniques are required for successful completion of this phase. Regular supervised jumping and landing are necessary in order to ensure symmetry and trunk alignment. Jumping drills should also focus on knee over toe position with quiet landings [44]. Primary jump and landing may be initiated on a level surface, with a hop onto a step or box added later (see Fig. 8.3b). The goal is to take off and land on the box without knee valgus. Gravity is arrested during the floor to box jump. In this stage, the athlete is not prepared to hop off the box. Running may be initiated with an antigravity treadmill, but traditional running should not start until 12 weeks following an injury [1].

Advancement to open-chain knee extension with resistance attached to proximal tibia for combined hamstring and quadriceps muscles may be emphasized within the home exercise program. Swiss ball bridges are effective in strengthening the gluteus maximus and hamstrings. A seated, elevated, resisted pattern triple flexion (hip, knee, ankle) lower extremity row, with opposite leg maintained in 90° knee flexion or knee extension, using a Thera-Band, provides strengthening of both extremities involved (see Fig. 8.3c, d).

Phase three milestones include running for 15 min without pain or effusion, single-leg hop with appropriate landing, and passing a functional test. Completion of phase three will typically demonstrate that an athlete may be functionally ready to return to sports based on their strength, balance, proprioception, and endurance. Some have advocated isokinetic testing in this age group at 60°/s [23, 50]. Isokinetic testing is a reliable form of testing strength in this age group [55, 56]. However, changes in isokinetic testing during development and maturation remain unclear [57]. A factor to consider in a young athlete is entering peak height velocity (PHV) along the developmental principals of Long-Term Athlete Development (LTAD) [58]. During ACL rehabilitation, a young athlete may demonstrate a large side-to-side deficit due to ongoing physiologic maturation that may occur in the uninjured extremity; making side-to-side differences is difficult to interpret. Another functional test is the series of single-leg hop tests described by Noyes et al. [59]; however, these have not been validated in the pediatric population.

The use of the Y-Balance Test™ (Functional Movement Systems, Chatham, Virginia) has gained popularity due to its ability to quantify strength, balance, proprioception, and a side-to-side difference in young athletes [60, 61]. A patient is tested by performing an excursion movement in three directions with his or her lower extremity, while maintaining a single leg stance with the contralateral extremity. The amount of excursion is compared to the amount of excursion on the contralateral leg and to age-matched normative values.

When interpreting a Y-Balance Test^™ (YBT) , a composite score of less than 90%, a side-to-side difference of 4 cm or greater in the anterior direction, or a side-to-side difference of 6 cm in the posteromedial and posterolateral directions has been correlated with a 2.5–3.5 times increase in lower extremity injury rates [60, 62, 63]. This method was validated by Lehr et al. 2013 in collegiate athletes [64]. Previous injury is a major risk factor and thus included in the composite score calculation. A consideration of the type of primary sport is also used in the composite score. The goal is a composite score of 100% for each lower extremity to minimize risk of injury.

Although not validated in the pediatric population, some providers have begun to use YBT as a functional tool in pediatric patients [48, 65]. Consideration for return to sports following rehabilitation of an ACL injury in a young patient may include a YBT composite score of greater than 90% and a side-to-side anterior difference of less than 4 cm.

At the completion of phase three milestones, athletes should be evaluated by their physician for sport participation clearance. The use of a functional brace during all pivoting activities is recommended for a minimum of 6 months from original injury [66]. Consideration of psychological readiness for return to play is made at this time. Psychosocial factors such as coping resources, emotional distress, social support, athletic identity, and fear of reinjury may have important roles in the recovery process after sport-related injuries [67–75]. An athlete’s psychological response to the injury and recovery process has an impact on return to sport and return to their previous level of activity after an ACL injury. Pediatric patients and their parents must be also counseled regarding the importance of reporting any activity-related effusion, mechanical symptom, or episodes of instability, as this may risk deterioration of joint function [49]. An annual YBT is recommended for ACL-deficient athletes [76].

Emphasis on maintenance program and injury prevention is paramount in this age group. An injury prevention program in the pediatric athlete interested in returning to pivoting sports should be tailored to be to the child’s physical and mental maturation level. Age-specific programs are guided by the principles of LTAD [48, 50, 58, 77]. Chapter 17 will review injury prevention programs for the pediatric athlete.

Historically, a functional brace was used as the primary treatment, along with activity modification, for an ACL injury in the skeletally immature athlete [24]. Today, the use of a functional brace remains an important adjunct to physical therapy in the nonoperative treatment of an ACL injury in this age group [6, 7, 17, 26, 39, 50, 51, 66, 78].

The use of a functional brace remains controversial in the treatment of the mature athlete with an ACL injury with or without a reconstruction. Half of all athletes with ACL deficiency will not be able to return to sports without a brace [33]. Although a brace may provide symptomatic relief of instability, a randomized trial in patients ages 18–50 years old with and without a brace did not demonstrate a difference in outcomes or conversion to surgery [32]. This may not be true for all sports or nonathletes [33]. Kocher et al. demonstrated a decrease in knee injuries in skiers who used a functional brace as opposed to those who did not while skiing. In this study, braced skiers had a 2% incidence of a new injury, while non-braced skiers had a 13% incidence (p = 0.005) [79].

Biomechanical models have demonstrated improvement in the anterior translation of the tibia with the use of the brace [80]. Rotational stability, particularly anterolateral rotational instability, is not supported by the use of a brace [81]. Regardless of the in vitro justification of the use of a functional ACL brace, a majority of patients with ACL deficiency have symptomatic relief with the use of a brace [33].

The use of a functional brace following an ACL tear in a skeletally immature patient is an important part of the treatment if they intend to return to athletic activity. Standard functional braces used in mature patients will typically not fit a young or prepubescent patient. The lack of physiologic quadriceps and gastrocsoleus muscle hypertrophy in the young ACL-deficient patient may not allow for standard ACL functional bracing that is commonly used in sports medicine practice. Few bracing manufacturers have developed pediatric-specific functional braces (see Table 8.2).