Modalities

In the immediate postoperative period (1–3 days), knee effusion must be controlled to avoid the quadriceps inhibition phenomenon. Electrogalvanic stimulation or high-voltage electrical muscle stimulation (EMS) may be used to augment the ice, compression, and elevation program to control swelling. This treatment uses the concept of like charges repelling. The effusion or swelling has a negative electrical charge, so using the negative electrodes at the knee and the positive (dispersive) electrode on either the low back or the opposite thigh will assist the body in removing the fluid from the joint to be reabsorbed. The treatment duration is approximately 30 minutes, the intensity is set to patient tolerance, and the treatment frequency is three to six times per day. Once the joint effusion is controlled, functional EMS is begun for muscle reeducation and quadriceps facilitation (Table 13-2).

The use of EMS to facilitate and enhance an adequate quadriceps contraction is based on the evaluation of quadriceps and vastus medialis oblique (VMO) muscle tone. One electrode is placed over the VMO and the second electrode is placed on the central to lateral aspect of the upper third of the quadriceps muscle belly (Fig. 13-1). The treatment duration is 20 minutes. The patient actively contracts the quadriceps muscle simultaneously with the machine’s stimulation. A portable EMS machine for home use may be required in individuals whose muscle rating is poor. EMS is continued until the muscle grade is rated as good.

FIGURE 13-1 Electrical muscle stimulation is used to facilitate and enhance an adequate quadriceps contraction early postoperatively.

Biofeedback therapy also has an important role in facilitating an adequate quadriceps muscle contraction early postoperatively. The surface electrode is placed over the selected muscle component to provide positive feedback to the patient and clinician regarding the quality of active or voluntary quadriceps contraction (Fig. 13-2). Biofeedback is also useful in enhancing hamstring relaxation if the patient experiences difficulty achieving full knee extension secondary to knee pain or muscle spasm. The electrode is placed over the belly of the hamstring muscle while the patient performs range of motion (ROM) exercises.

FIGURE 13-2 Biofeedback therapy is implemented to facilitate an adequate quadriceps muscle contraction early postoperatively.

The most widely used modality after ACL reconstruction is cryotherapy, which is begun in the recovery room after surgery. Cost of various cryotherapy options and patient compliance are two major factors in the successful control of postoperative pain and swelling. The standard method of cold therapy is an ice bag or commercial cold pack, which is kept in the freezer until required. Empirically, patients prefer motorized cooler units (Fig. 13-3). These units maintain a constant temperature and circulation of ice water through a pad, which provides excellent pain control. Gravity flow units are also effective; however, temperature maintenance is more difficult with these devices than with the motorized cooler units. The temperature can be controlled by using gravity to backflow and drain the water, refilling the cuff with fresh ice water as required. Cryotherapy is used for 20 minutes at a time from three times a day to every waking hour depending upon the extent of pain and swelling. In some cases, the treatment time is extended owing to the thickness of the buffer used between the skin and the device. The motorized units contain a thermostat, which is helpful when cold therapy is used for an extended treatment time. Vasopneumatic devices offer another option for cold therapy. The Game Ready device (Game Ready, Berkeley, CA) allows the clinician to set the temperature and, as well, one of four different compression levels depending on patient tolerance. Although this is primarily a clinical treatment tool, it may be used at home as well. Cryotherapy is typically done after exercise or when required for pain and swelling control and is maintained throughout the entire postoperative rehabilitation protocol.

FIGURE 13-3 A motorized cooler unit used to provide cryotherapy.

Postoperative Bracing

The use of postoperative braces after ACL reconstruction represents a controversial area. Screening patients for personality type, pain tolerance, and program compliance may provide insight into the individual who will require brace protection postoperatively. The primary indication for the use of a brace is protection of the patient during weight-bearing in the event of a fall and to initiate early, more comfortable weight-bearing during the first few postoperative weeks. The brace should be rigid in nature and the knee held initially at 0° (Fig. 13-4). The brace is opened based on the protocol to allow normal knee flexion during ambulation. Periodic evaluation of the brace and its position on the leg must be done to ensure maximal benefit is achieved. The authors do not routinely prescribe a derotation or functional knee brace upon return to full activities after ACL reconstruction for patients in this protocol.

FIGURE 13-4 A long-leg postoperative brace protects the patient during weight-bearing in the event of a fall and promotes early, comfortable weight-bearing during the first few postoperative weeks.

Range of Knee Motion

The goal in the 1st postoperative week is to obtain a ROM of 0° to 90°. A continuous passive motion machine is not required or routinely used by the authors. Patients perform passive and active ROM exercises in a seated position for 10 minutes a session, approximately four to six times per day (Fig. 13-5).

FIGURE 13-5 Passive (A and B) and active range of motion exercises in a seated position.

Full passive knee extension must be obtained immediately to avoid excessive scarring in the intercondylar notch and posterior capsular tissues. If the patient has difficulty regaining at least 0° by the 7th postoperative day, he or she begins an overpressure program. The foot and ankle are propped on a towel or other device to elevate the hamstrings and gastrocnemius that allows the knee to drop into full extension (Fig. 13-6A). This position is maintained for 10 minutes and repeated four to six times per day. A 10-pound weight may be added to the distal thigh and knee to provide overpressure to stretch the posterior capsule. Full knee extension should be obtained by the 2nd postoperative week. If this is not accomplished, or if the clinician notes a firm end feel, then an extension board (see Fig. 13-6B) or additional weight of 15 to 20 pounds is used six times a day. If this is still not effective, a drop-out cast (see Fig. 13-6C) is implemented for 24 to 36 hours for continuous extension overpressure. The goal is to obtain 0° to 2° to 3° of hyperextension, which is in the normal knee motion limit. In patients with physiologic bilateral knee hyperextension, the authors recommend the gradual return of 3° to 5° of hyperextension in the reconstructed knee to more closely resemble the amount of hyperextension present in the contralateral knee. However, the authors do not recommend that the patient regain more than 5° of hyperextension owing to potentially deleterious forces that may be placed on the healing graft.

FIGURE 13-6 Overpressure program for extension. A, Hanging weight exercise. B, Extension board. C, Drop-out cast.

Knee flexion is gradually increased to 120° by the 3rd to 4th postoperative week and 135° by the 5th to 6th postoperative week. Passive knee flexion exercises are performed initially in the traditional seated position, using the opposite lower extremity to provide overpressure. Other methods to assist in achieving flexion greater than 90° include chair rolling (Fig. 13-7A), wall slides (see Fig. 13-7B and C), knee flexion devices (see Fig. 13-7D), and passive quadriceps stretching exercises. Patients who have difficulty achieving 90° by the 4th week require a gentle ranging of the knee under anesthesia (not a forceful manipulation) as described in Chapter 41, Prevention and Treatment of Knee Arthrofibrosis.

FIGURE 13-7 Overpressure program for flexion. A, Rolling stool exercise. B and C, Wall slides. D, Overpressure flexion device.

Patellar Mobilization

Maintaining normal patellar mobility is critical to regain a normal range of knee motion. The loss of patellar mobility is often associated with arthrofibrosis and, in extreme cases, the development of patella infera.^18–20 Patellar glides are performed beginning the 1st postoperative day in all four planes (superior, inferior, medial, and lateral) with sustained pressure applied to the appropriate patellar border for at least 10 seconds (Fig. 13-8). This exercise is performed for 5 minutes before ROM exercises. Caution is warranted if an extensor lag is detected, because this may be associated with poor superior migration of the patella, indicating the need for additional emphasis on this exercise. Patellar mobilization is performed for approximately 6 weeks postoperatively.

FIGURE 13-8 Patellar glides are begun the first postoperative day in all four planes: A, Superior and inferior. B, Medial and lateral.

Weight-Bearing

Partial weight-bearing is permitted immediately postoperatively as long as pain and swelling are controlled and a voluntary quadriceps contraction is demonstrated. Initially, bilateral crutches may be used and 50% body weight is placed on the involved foot. The amount of weight the patient is allowed to place on the involved limb is progressed as tolerated to allow full weight-bearing by the 3rd to 4th postoperative week. Importantly, a normal gait pattern is advocated that avoids a locked knee position and encourages normal knee flexion throughout the gait cycle. This technique allows for normal patterning of heel-to-toe ambulation, quadriceps contraction during midstance, and hip and knee flexion during the gait cycle. The locked-knee position is avoided owing to the potential for the development of a quadriceps-avoidance gait pattern.

Flexibility

Hamstring and gastrocnemius-soleus flexibility exercises are begun the 1st day after ACL reconstruction. A sustained static stretch is held for 30 seconds and repeated five times. The most common hamstring stretch is the modified hurdler stretch (Fig. 13-9), and the most common gastrocnemius-soleus stretch is the towel pull (Fig. 13-10). These exercises help control pain owing to the reflex response created in the hamstrings when the knee is kept in the flexed position. As well, the towel-pulling exercise can help lessen discomfort in the calf, Achilles tendon, and ankle. These stretches represent critical components of the knee extension ROM program, because the ability to relax these two muscle groups is imperative to achieve full passive knee extension.

FIGURE 13-9 Hamstring modified hurdler stretch.

FIGURE 13-10 Gastrocnemius-soleus towel pull stretch.

Quadriceps (Fig. 13-11) and iliotibial band (Fig. 13-12) flexibility exercises are performed to assist in achieving full knee flexion and controlling lateral hip and thigh tightness. A complete evaluation of the lower extremity will reveal deficit areas in flexibility that should be corrected. When designing a flexibility program, the therapist should take into account the particular sport or activity the patient wishes to return to as well as the position or physical requirements of that activity. Flexibility is incorporated in the maintenance program the patient performs once discharged.

FIGURE 13-11 Quadriceps stretch.

FIGURE 13-12 Iliotibial band stretch.

Strengthening

The strengthening program is begun on the first postoperative visit. Early emphasis on the generation of a good voluntary quadriceps contraction is critical for a successful and safe return to functional activity. Isometric quadriceps contractions are completed on an hourly basis following the repetition rules of 10-second holds, 10 repetitions, 10 times per day. Adequate evaluation of the quadriceps contraction by both the therapist and the patient is critical. The patient can monitor contractions by visual or manual means, comparing the quality of the contractions with those achieved by the contralateral limb. The patient can also assess the superior migration of the patella during the contraction, which should be approximately 1 cm, and the inferior migration of the patella during the initial relaxation of the contraction. The patient must not let the knee go into hyperextension during isometric contractions, but hold the knee flexion position throughout the exercise. If necessary, biofeedback can also be used to reinforce a good quadriceps contraction.

Straight leg raises are initiated the 1st postoperative day in the four planes of hip movement. The adduction straight leg raise has a beneficial effect on the VMO. Supine straight leg raises must include a sufficient isometric quadriceps contraction to benefit the quadriceps. Straight leg raises in the other two planes are also important for proximal stabilization. As these exercises become easy to perform, ankle weights are added to progress muscle strengthening. Initially, 1 to 2 pounds of weight is used, and eventually, up to 10 pounds is added as long as this is not more than 10% of the patient’s body weight. Active-assisted ROM can also be used to facilitate the quadriceps muscle if poor tone is observed during isometric contractions. These exercises are primarily used during the first 8 postoperative weeks in which emphasis is placed on controlling pain and swelling, regaining full ROM, achieving early quadriceps control and proximal stabilization, and resuming a normal gait pattern.

Closed kinetic chain exercises are initiated the 1st postoperative week. Mini-squats from 0° to 45° (Fig. 13-13A) are begun when tolerated by the patient. Initially, the patient’s body weight is used as resistance and gradually, TheraBand (see Fig. 13-13B) or surgical tubing is employed as a resistance mechanism. Quick, smooth, rhythmic squats are performed to a high-set/high-repetition cadence to promote muscle fatigue. Hip position is important to monitor in order to promote a quadriceps contraction.

FIGURE 13-13 Minisquats from 0° to 45° using the patient’s body weight (A) and TheraBand (B) for increased resistance.

Toe-raises for gastrocnemius-/soleus strengthening and wall-sitting isometrics for quadriceps control are begun the 2nd postoperative week. The goal of wall-sitting is to improve quadriceps contraction by performing the exercise to muscle exhaustion (Fig. 13-14A). If anterior knee pain is experienced, it may be decreased by either altering the knee flexion angle of the sit or subtly changing the toe-out/toe-in angle by no more than 10°. The exercise may also be modified to produce greater challenge to the quadriceps. The patient may voluntarily set the quadriceps muscle once she or he reaches the maximum knee flexion angle, which is typically between 30° and 45°. This contraction and knee flexion position are held until muscle fatigue occurs and the exercise is repeated three to five times. The patient may squeeze a ball between the distal thighs, inducing a hip adduction contraction and a stronger VMO contraction (see Fig. 13-14B). In a third variation, the patient holds dumbbell weights in the hands to increase body weight, which promotes an even stronger quadriceps contraction (see Fig. 13-14C). Finally, the patient can shift the body weight over the involved side to stimulate a single-leg contraction. This exercise is promoted as an excellent one for the patient to perform at home four to six times a day to achieve quadriceps fatigue in a safe knee flexion angle that does not induce an abnormal anterior tibial translation.

FIGURE 13-14 A, Wall sitting to muscle exhaustion. B, Squeezing a ball between the distal thighs induces a hip adduction contraction and a stronger vastus medialis obliquus contraction. C, Use of dumbbell weights to increase body weight promotes an even stronger quadriceps contraction.

Lateral step-ups are begun when the patient has achieved full weight-bearing (Fig. 13-15). The height of the step is gradually increased based on patient tolerance.

FIGURE 13-15 The step-up exercise.

Hamstring curls are begun with Velcro ankle weights within the first few weeks and eventually advanced to weight machines (Fig. 13-16). Weight machines are advantageous owing to the muscle isolation obtained as the machine provides stability to the knee joint. The patient exercises the involved limb alone as well as both limbs together. If the lightest amount of weight on the machine is too heavy to be lifted by the involved limb alone, the exercise may be performed as an eccentric contraction in which the patient lifts the weight with both legs and lowers the weight with the involved side. Eccentric contractions may also be used in the advanced stages of strength training. Hamstring strength is critical to the overall success of the rehabilitation program because of the role that this musculature plays in the dynamic stabilization of the knee joint. Weight training is used throughout the advanced program and continues in the return-to-activity and maintenance phases of rehabilitation.

FIGURE 13-16 A and B, Hamstring curls.

Open kinetic chain extension exercises are incorporated within the first few weeks to further develop quadriceps muscle strength. Caution is warranted because of the potential problems these exercises may create for the healing graft and the patellofemoral joint. Resisted knee extension is begun with Velcro ankle weights in the 1st week from 90° to 30°. The terminal phase of extension is avoided because of the forces placed on the patellofemoral joint and ACL graft. The patellofemoral joint must be monitored for changes in pain, swelling, and crepitus to avoid a patellar conversion in which painful patellofemoral crepitus develops with articular cartilage damage. The surgeon should advise the therapist if there are abnormal patellofemoral findings of joint damage.

A full lower extremity–strengthening program is critical for early and long-term success of the rehabilitation program. Other muscle groups included in this routine are the hip abductors, hip adductors, hip flexors, and hip extensors. These muscle groups can be exercised on either a multi-hip or cable system machine (Fig. 13-17) or a hip abductor-adductor machine. Gastrocnemius-soleus strength is a key component for both early ambulation and the running program. In addition, upper extremity and core strengthening are important for a safe and effective return to work or sports. Sport and position specificity are taken into account when devising the strengthening program to maximize its benefits. Kraemer and Ratamess⁶ provided the recommendations for progression of muscle strength, hypertrophy, power, and endurance training according to the American College of Sports Medicine¹ (Tables 13-3 to 13-6). Specific strengthening and sports-specific timing drills are beyond the scope of this chapter; however, the therapist should work with the patient and appropriate coaches to determine the individual patient’s program.

FIGURE 13-17 A–D, Multi-hip cable system machine.

Balance, Proprioceptive, and Perturbation Training

Balance and proprioceptive training are initiated the 1st postoperative week. Initially, the patient simply stands and shifts weight from side-to-side and front-to-back. This activity encourages confidence in the leg’s ability to withstand the pressures of weight-bearing and initiates the stimulus to knee joint position sense.

Cup-walking is begun when the patient achieves full weight-bearing (Fig. 13-18) to promote symmetry between the surgical and the uninvolved limbs. This exercise helps develop hip and knee flexion and quadriceps control during midstance of gait to prevent knee hyperextension. In addition, cup-walking controls hip and pelvic motion during midstance, gastrocnemius-soleus activity during push-off, and excessive hip hiking. These components of gait control are critical in the early phases of rehabilitation to decrease forces on the healing graft.

FIGURE 13-18 Cup walking to promote symmetry between the reconstructed and the uninvolved limbs.

Double- and single-leg balance exercises in the stance position are beneficial early postoperatively. During the single-leg exercise, the foot is pointed straight ahead, the knee flexed 20° to 30°, the arms extended outward to horizontal, and the torso positioned upright with the shoulders above the hips and the hips above the ankles (Fig. 13-19A). The objective is to remain in this position until balance is disturbed. A minitrampoline or unstable platform may be used to make this exercise more challenging, because these devices promote greater dynamic limb control than that required to stand on a stable surface (see Fig. 13-19B). To provide a greater challenge, patients may assume the single-leg stance position and throw/catch a weighted ball against an inverted minitrampoline (Fig. 13-20) until fatigue occurs.

FIGURE 13-19 Single-leg balance exercise performed first on a stable surface (A) and then on an unstable surface (B).

FIGURE 13-20 A and B, Single-leg balance exercise in which the patient throws and catches a weighted ball against an inverted minitrampoline.

Perturbation-training techniques are initiated at approximately the 7th to 8th postoperative week during balance exercises. The therapist stands behind the patient and disrupts her or his body posture and position periodically to enhance dynamic knee stability. The techniques involve either direct contact with the patient (Fig. 13-21A) or disruption of the platform the patient is standing on (see Fig. 13-21B).

FIGURE 13-21 Perturbation training involving direct contact with the patient (A) and disruption of the platform the patient is standing on (B).

Half foam rolls are also used in this time period as part of the gait-retraining and balance program (Fig. 13-22). This exercise helps the patient develop balance and dynamic muscular control required to maintain an upright position and be able to walk from one end of the roll to the other. A center of balance, limb symmetry, quadriceps control in midstance, and postural positioning are benefits developed through this type of training. Use of the Biomechanical Ankle Platform System (Camp, Jackson, MI) in double-leg and single-leg stance is another effective balance and proprioceptive exercise (Fig. 13-23).

FIGURE 13-22 Gait and balance retraining using half foam rolls.

FIGURE 13-23 The Biomechanical Ankle Platform System (Camp, Jackson, MI) is used in double-leg and single-leg stance.

The use of more expensive devices adds another dimension to the proprioception program, because certain units objectively attempt to document balance and dynamic control. Two of the more common units include balance systems from Biodex (Fig. 13-24) (Biodex Medical Systems, Inc., Shirley, NY) and Neurocom (Neurocom, Clackamas, OR).

FIGURE 13-24 The Biodex Balance System (Biodex Medical Systems, Inc., Shirley, NY) may be used for balance training and to objectively measure balance and dynamic control.

Conditioning

The primary consideration for a conditioning program throughout the rehabilitation period is to stress the cardiovascular system without compromising the knee joint. Depending on accessibility, a cardiovascular program is begun as soon as the patient can sufficiently tolerate the upright position with an upper extremity ergometer. The surgical limb should be elevated to minimize lower extremity swelling. This exercise is performed as tolerated. Stationary bicycling is begun in the 3rd postoperative week. Water walking may be initiated when the surgical wound has healed. Early goals of these programs include facilitation of full ROM, gait retraining, and cardiovascular reconditioning. In order to improve cardiovascular endurance, the program should be performed at least three times per week for 20 to 30 minutes, and the exercise should be performed to at least 60% to 85% of maximal heart rate. It is generally regarded that performing in the higher levels of percentage of maximal heart rate achieves greater cardiovascular efficiency and endurance.

Cross-country ski and stair-climbing machines are permitted during the 5th to 6th postoperative weeks. Protection against high stresses to the patellofemoral joint is strongly advocated. During bicycling, the seat height is adjusted to its highest level based on patient body size and a low resistance level is used initially. Stair-climbing machines are adjusted to produce a short step and low resistance.

An effective cardiovascular exercise program is an important component of the latter phases of rehabilitation. In addition to the previously described exercises, an aquatic program that includes lap work using freestyle or flutter kicking, water walking, water aerobics, and deep-water running is encouraged. Determining which cardiovascular exercises are appropriate is based on each patient’s access to and preference for specific equipment.

Running and Agility Program

In order to initiate the running program, the patient must demonstrate no more than a 30% deficit in average torque for the quadriceps and hamstrings on isokinetic testing, have no more than 3 mm of increase in AP displacement on arthrometer testing, and be at least 9 weeks postoperative. It is important to note that the majority of patients initiate running at approximately 16 to 20 weeks postoperative. Only in exceptional cases does this program begin before this time period at which muscle strength has returned to normal, no pain or joint effusion is present, and no concurrent operative procedures were performed such as a complex meniscus repair or other ligament reconstruction.

The running program is designed based on the patient’s athletic goals, particularly the position or physical requirements of the activity. For instance, an individual returning to short- duration, high-intensity activities should participate in a sprinting program rather than a long-distance endurance program. The running program is performed three times per week, on opposite days of the strength program. Because the running program may not reach aerobic levels initially, a cross-training program is used to facilitate cardiovascular fitness. The cross- training program is performed on the same day as the strength workout.

The first level consists of straight-ahead walk/run combinations. Running distances are 20, 40, 60, and 100 yards (18, 37, 55, 91 m) in both forward and backward directions. The initial running speed is approximately one quarter to one half of the patient’s normal speed, which gradually progresses to three quarters to full speed. An interval-training–rest approach is applied in which the rest phase is two to three times the length of the training phase. After the patient is able to run straight ahead at full speed, lateral running and crossover maneuvers are begun. Short distances, such as 20 yards (18 m), are used to work on speed and agility. Side-to-side running over cups may be used to facilitate proprioception. At this time, sports-specific equipment is introduced to enhance skill development (e.g., a soccer ball for a soccer player to work on dribbling and passing activities). These variations are useful to motivate the patient and minimize training boredom.

The third level of the running program incorporates figure-eight running drills. Long and wide movement patterns over 20 yards (18 m) are initially used to encourage subtle cutting. As speed and confidence improve, the distance is decreased to approximately 10 yards (9 m). Progression through this phase is similar to that used in the lateral side-to-side program just described. Speed and agility are emphasized, and equipment is introduced to develop sports-specific skills.

The fourth phase in the running program introduces cutting patterns. These patterns include directional changes at 45° and 90° angles, which allow the patient to progress from subtle to sharp cuts.

Plyometric Training

Plyometric training is begun upon successful completion of the running program in order to minimize bilateral alterations in neuromuscular function and proprioception. Important parameters to consider when performing plyometric exercises include surface, footwear, and warm-up. The jump training should be done on a firm, yet forgiving surface such as a wooden gym floor. Very hard surfaces like concrete should be avoided. A cross-training or running shoe should be worn to provide adequate shock absorption as well as adequate stability to the foot. Checking wear patterns and outer sole wear will help avoid overuse injuries.

During the various jumps, the patient is instructed to keep the body weight on the balls of the feet and to jump and land with the knees flexed and shoulder-width apart to avoid knee hyperextension and an overall valgus lower limb position (Fig. 13-25). The patient should understand that the exercises are reaction and agility drills and, although speed is emphasized, correct body posture must be maintained throughout the drills.

FIGURE 13-25 During plyometric training, the patient is instructed to keep the body weight on the balls of the feet, to jump and land with the knees flexed and shoulder-width apart to avoid knee hyperextension and an overall valgus lower limb position, as shown here.

The first exercise is level-surface box-hopping using both legs. A four-square grid of four equally sized boxes is created with tape on the floor. The patient is instructed to first hop from box 1 to box 3 (front-to-back; Fig. 13-26), and then from box 1 to box 2 (side-to-side; Fig. 13-27). The second level incorporates both of these directions into one sequence and also includes hopping in both right and left directions (e.g., box 1 to box 2 to box 4 to box 2 to box 1). Level three progresses to diagonal hops (Fig. 13-28), and level four includes pivot hops in 90° and 180° directions (Fig. 13-29). Once the patient can perform level four double-leg hops, the same exercises are done on a single leg. The next phase incorporates vertical box hops.

FIGURE 13-26 A–C, Initial plyometric training, jumping front-to-back on a level surface using both legs.

FIGURE 13-27 A–C, Initial plyometric training, jumping side-to-side on a level surface using both legs.

FIGURE 13-28 A–C, Plyometric training using diagonal hops, forward and backward.

FIGURE 13-29 A–C, Plyometric training using pivot hops in 90° and 180° directions.

It is important to stress that plyometric exercise is intense and adequate rest must be included in the program. Individual sessions can be performed in a manner similar to that for interval training. Initially, the rest period lasts two to three times the length of the exercise period and is gradually decreased to one to two times the length of the exercise period. Plyometric training is performed two to three times weekly.

Improvement is measured by counting the number of hops in a defined time period. The initial exercise time period is 15 seconds. The patient is asked to complete as many hops between the squares as possible in 15 seconds. Three sets are performed for both directions and the number of hops recorded. The program is progressed as the number of hops increases, as does patient confidence.

The authors recommend that patients complete a course of Sportsmetrics training to reduce the risk of a noncontact reinjury before return to strenuous athletics. This training program teaches athletes to control the upper body, trunk, and lower body position; lower the center of gravity by increasing hip and knee flexion during activities; and develop muscular strength and techniques to land with decreased ground reaction forces. In addition, athletes are instructed to pre-position the body and lower extremity prior to initial ground contact in order to obtain the position of greatest knee joint stability and stiffness. The program consists of a dynamic warm-up, plyometric jump training, strengthening exercises, aerobic conditioning, agility, and risk-awareness training. The training is conducted three times a week on alternating days for 6 weeks and is described in detail in Chapter 19, Decreasing the Risk of ACL Injuries in Female Athletes.

Once the patient has completed the running and plyometric programs and strength and function testing reach normal values, return to sports is allowed. A trial of function is encouraged in which the patient is monitored for knee swelling, pain, overuse symptoms, and giving-way episodes. Some athletes will experience transient knee swelling upon return to strenuous activities and should be educated on how to recognize this problem and the importance of reducing activities until the swelling subsides. If swelling persists, the athlete is advised to reduce athletics for 2 to 6 weeks, consider use of nonsteroidal anti-inflammatories, and use ice and elevation. Upon successful return to activity, the patient is encouraged to continue with a maintenance program. During the in-season, a conditioning program of two workouts a week is recommended. In the off-season or preseason, this program should be performed three times a week to maximize gains in flexibility, strength, and cardiovascular endurance.