CHAPTER 21

Rehabilitation of Knee Injuries

Michelle C. Boling, PhD, LAT, ATC
Darin A. Padua, PhD, ATC
William E. Prentice, PhD, PT, ATC, FNATA

Figure 21-1. Anatomy of the knee—anterior view.

FUNCTIONAL ANATOMY AND BIOMECHANICS

A rehabilitation program for an injured knee must be built on the clinician’s understanding of the functional anatomy and biomechanics of that joint.181 The knee is part of the kinetic chain and is directly affected by motions and forces occurring in and being transmitted from the foot, ankle, and lower leg. In turn, the knee must transmit forces to the thigh, hip, pelvis, and spine.¹⁷⁰ Abnormal forces that cannot be distributed must be absorbed by the tissues. In a closed kinetic chain (CKC), forces must be either transmitted to proximal segments or absorbed in a more distal joint. The inability of this closed system to dissipate these forces typically leads to a breakdown in some part of the system. Certainly, as part of the kinetic chain, the knee joint is susceptible to injury resulting from absorption of these forces. The knee is commonly considered a hinge joint because its 2 principal movements are flexion and extension (Figures 21-1 and 21-2). However, the knee is capable of movement in 6 degrees of freedom—3 rotations and 3 translations—thus the knee joint is truly not a hinge joint. The stability of the knee joint depends primarily on the ligaments, the joint capsule, and muscles that surround the joint.¹⁸⁰ The knee is designed primarily to provide stability in weightbearing and mobility in locomotion; however, it is especially unstable laterally and medially.

Movement between the tibia and the femur involves the physiological motions of flexion, extension, and rotation, as well as arthrokinematic motions including rolling and gliding. As the tibia extends on the femur, the tibia glides and rolls anteriorly. If the femur is extending on the tibia, gliding occurs in an anterior direction, whereas rolling occurs posteriorly. Axial rotation of the tibia relative to the femur is an important component of knee motion. In the “screw home” mechanism of the knee, as the knee extends, the tibia externally rotates. Rotation occurs because the medial femoral condyle is larger than the lateral femoral condyle. When weightbearing, the femur must internally rotate on the tibia to achieve full knee extension because the tibia is fixed. The rotational component gives a great deal of stability to the knee in full extension. When weightbearing, the popliteus muscle must contract and externally rotate the femur to “unlock” the knee so that flexion can occur.

Figure 21-2. Anatomy of the knee—posterior view.

Collateral Ligaments

The medial collateral ligament (MCL) is divided into 2 parts—the stronger superficial portion and the thinner and weaker “deep” medial ligament or capsular ligament, with its accompanying attachment to the medial meniscus.179 The superficial position of the MCL is separate from the deeper capsular ligament at the joint line. The posterior aspect of the ligament blends into the deep posterior capsular ligament and semimembranosus muscle. Fibers of the semimembranosus muscle go through the capsule and attach to the posterior aspect of the medial meniscus, pulling it backward during knee flexion. The MCL functions as the primary static stabilizer against valgus stress. The MCL is taut at full extension and begins to relax between 15 to 20 degrees of flexion and comes under tension again at 60 to 70 degrees of flexion, although a portion of the ligament is taut throughout the range of motion (ROM).^10,92,159 Its major purpose is to prevent the knee from valgus and external rotating forces.

The MCL was thought to be the principal stabilizer of the knee in a valgus position when combined with rotation. In the normal knee, valgus loading is greatest during the push-off phase of gait when the foot is planted and the tibia is externally rotated relative to the femur. It is now known that the anterior cruciate ligament (ACL) plays an equal or greater part in this function.¹⁶⁸ The lateral collateral ligament (LCL) is a round, fibrous cord about the size of a pencil. It is attached to the lateral epicondyle of the femur and to the head of the fibula. The LCL functions with the iliotibial band, the popliteous tendon, the arcuate ligament complex, and the biceps femoris tendon to support the lateral aspect of the knee. The LCL is under constant tensile loading, and the thick, firm configuration of the ligament is well designed to withstand this constant stress.⁹² The LCL is taut during knee extension but relaxed during flexion.

Clinical Decision-Making Exercise 21-1

A high school football player suffered an isolated grade 2 sprain of his MCL 3 days ago. At the emergency room, the X-ray result was negative, and he was given a straight-leg immobilizer and crutches. He was instructed to begin walking after 1 week and return to play when the pain subsides. He has never before sustained a knee injury and is having difficulty regaining pain-free ROM. He has been referred to the athletic trainer in the local sports medicine clinic. What can the athletic trainer do to help increase ROM in the patient’s injured leg?

Capsular Ligaments

The deep medial capsular ligament is divided into 3 parts: the anterior, medial, and posterior capsular ligaments. The anterior capsular ligament connects with the extensor mechanism and the medial meniscus through the coronary ligaments. It relaxes during knee extension and tightens during knee flexion. The primary purposes of the medial capsular ligaments are to attach the medial meniscus to the femur and to allow the tibia to move on the meniscus inferiorly. The posterior capsular ligament is called the posterior oblique ligament. It attaches to the posterior medial aspect of the meniscus and intersperses with the semimembranosus muscle. Along with the MCL, the pes anserinus tendons, and the semimembranosus, the posterior oblique ligament reinforces the posteromedial joint capsule.

The arcuate ligament is formed by a thickening of the posterolateral capsule. Its posterior aspect attaches to the fascia of the popliteal muscle and the posterior horn of the lateral meniscus. The arcuate ligament and the iliotibial band, the popliteus, the biceps femoris, and the LCL reinforce the posterolateral joint capsule.

The iliotibial band becomes taut during both knee extension and flexion. The popliteal muscle stabilizes the knee during flexion and, when contracting, protects the lateral meniscus by pulling it posteriorly. The biceps femoris muscle also stabilizes the knee laterally by inserting into the fibular head, iliotibial band, and capsule.

Cruciate Ligaments

The ACL prevents the tibia from moving anteriorly during weightbearing, stabilizes the knee in full extension, and prevents hyperextension. It also stabilizes the tibia against excessive internal rotation and serves as a secondary restraint for valgus/varus stress with collateral ligament damage. The ACL works in conjunction with the thigh muscles, especially the hamstring muscle group, to stabilize the knee joint.

During extension, there is external rotation of the tibia during the last 15 degrees of the ACL unwinding. In full extension, the ACL is tightest, and it loosens during flexion. When the knee is fully extended, the posterolateral portion of the ACL is tight. In flexion, the posterolateral fibers loosen and the anteromedial fibers tighten.

Some portion of the posterior cruciate ligament (PCL) is taut throughout the full ROM. As the femur glides on the tibia, the PCL becomes taut and prevents further gliding. In general, the PCL prevents excessive internal rotation. Hyperextension of the knee guides the knee in flexion, and the PCL acts as a drag during the initial glide phase of flexion.

Menisci

The medial and lateral menisci function to improve the stability of the knee, increase shock absorption, and distribute weight over a larger surface area. The menisci help to stabilize the knee, specifically the medial meniscus, when the knee is flexed at 90 degrees. The menisci transmit one-half of the contact force in the medial compartment and an even higher percentage of the contact load in the lateral compartment.

During flexion the menisci move posteriorly, and during extension they move anteriorly, primarily due to attachments of the medial meniscus to the semimembranosus and the lateral meniscus to the popliteus tendon. During internal rotation, the medial meniscus moves anteriorly relative to the medial tibial plateau, and the lateral meniscus moves posteriorly relative to the lateral tibial plateau. In external rotation, the movements are reversed.

The Function of the Patella

Collectively, the quadriceps muscle group, the quadriceps tendon, the patella, and the patellar tendon, form the extensor mechanism. The patella aids the knee during extension by lengthening the lever arm of the quadriceps muscle. It distributes the compressive stresses on the femur by increasing the contact area between the patellar tendon and the femur.140 It also protects the patellar tendon against friction. Tracking within this groove depends on the pull of each quadriceps muscle, patellar tendon, retinacular and patellofemoral ligaments, depth of the femoral condyles, and shape of the patella.

During full extension the patella lies slightly lateral and proximal to the trochlea. At 20 degrees of knee flexion, there is tibial rotation, and the patella moves into the trochlea. At 30 degrees, the patella is most prominent. At 30 degrees and more, the patella moves deeper into the trochlea. At 90 degrees, the patella again becomes positioned laterally. When knee flexion is 135 degrees, the patella has moved laterally beyond the trochlea.¹⁴⁰

Muscle Actions

For the knee to function properly, numerous muscles must work together in a highly complex and coordinated fashion. Knee movement requires various lower extremity muscles to act as agonists, antagonists, synergists, stabilizers, and neutralizers and to act as force couples to produce force, reduce force, and dynamically stabilize the knee.³⁶ Traditional rehabilitation has focused on uniplanar force production movements, yet athletic movement demands required multiplanar force with various muscular requirements. Following is a list of knee actions and the muscles that are involved in the agonist movement action, but athletic trainers also need to take into account the various muscle demands for proper movement production.

• Knee flexion is executed by the biceps femoris, semitendinosus, semimembranosus, gracilis, sartorius, gastrocnemius, popliteus, and plantaris muscles.
  
• Knee extension is executed by the quadriceps muscle of the thigh, consisting of 3 vasti—the vastus medialis, vastus lateralis, and vastus intermedius—and by the rectus femoris.
  
• External rotation of the tibia is controlled by the biceps femoris. The bony anatomy also produces external tibial rotation as the knee moves into extension.
  
• Internal rotation is accomplished by the popliteus, semitendinosus, semimembranosus, sartorius, and gracilis muscles. Rotation of the tibia is limited and can occur only when the knee is in a flexed position.
  
• The iliotibial band on the lateral side primarily functions as a dynamic lateral stabilizer and weak knee flexor.

REHABILITATION TECHNIQUES FOR THE KNEE JOINT

After injury to the knee, some loss of motion is likely. This loss can be caused by the effects of the injury, the trauma of surgery, or the effects of immobilization. Ligaments do not heal completely for 18 to 24 months, yet periarticular tissue changes can begin within 4 to 6 weeks of immobilization.⁹⁰ This is marked histologically by a decrease in water content in collagen and by an increase in collagen crosslinkage.⁹⁰ The initiation of an early ROM program can minimize these harmful changes (Figures 21-3 through 21-17). Controlled movement should be initiated early in the recovery process and progress based on healing constraints and patient tolerance toward a normal range of about 0 to 130 degrees.

Pitfalls that can slow or prevent regaining normal ROM include joint effusion, imperfect surgical technique (improper placement of an anterior cruciate replacement), development of joint capsule or ligament contracture, and muscular resistance caused by pain.^65,90 The surgeon must address motion lost from technique, but the athletic trainer can successfully deal with motion lost from soft tissue contracture or muscular resistance.

REHABILITATION EXERCISES FOR THE KNEE COMPLEX

Stretching Exercises

Figure 21-3. Active knee slides on table.

Figure 21-4. Active-assisted knee slides use the good leg supporting the injured knee to regain flexion and extension.

Figure 21-5. Wall slides are done to regain knee flexion and extension.

Figure 21-6. Active-assisted knee slides on wall.

Figure 21-8. Knee extension in prone position with an ankle weight around the foot is used to regain extension.

Figure 21-9. Groin stretch. Muscles: adductor magnus, longus, and brevis; pectineus; gracilis.

Figure 21-10. Side-lying knee extensor stretch using sport cord.

Figure 21-15. Knee flexor stretch using sport cord.

Figure 21-16. Knee flexor stretch against wall.

Isotonic Open Kinetic Chain Exercises

Figure 21-18. Hip abduction. Used to strengthen the gluteus medius and tensor fascia lata, which share a common tendon, the iliotibial band. The tensor fascia lata serves as a weak knee flexor and helps to provide stability laterally. Weight may be above knee as well.

Figure 21-19. Hip adduction. Used to strengthen the adductor magnus, longus, and brevis; pectineus; and gracilis. The gracilis is the only one of the hip adductors to cross the knee joint. Weight placed above knee eliminates the gracilis.

Figure 21-21. Straight leg raising is done early in the rehabilitation for active contraction of the quadriceps.

Figure 21-22. Knee flexion. Primary muscles: biceps femoris, semimembranosus, semitendinosus. Secondary muscles: gracilis, gastrocnemius, sartorius, popliteus. Note: Biceps femoris is best strengthened with tibia rotated externally; semimembranosus and semitendinosus muscles are best strengthened with tibia rotated internally. (Reprinted with permission from Matrix Fitness.)

Closed Kinetic Chain Strengthening Exercises

Figure 21-24. Ankle plantar flexion standing on box. Primary muscles: gastrocnemius, soleus.

Figure 21-25. Mini-squat performed in 0- to 40-degree range.

Figure 21-27. Lunges are done to strengthen the quadriceps eccentrically.

Figure 21-28. Lunges performed at different angles of the “clock face.” Maintain a good squat position in each direction.

Figure 21-29. Leg-press exercise. The seat may be adjusted to whatever knee joint angle is appropriate. (Reprinted with permission from Reyes Fitness.)

Figure 21-31. Terminal knee extensions using surgical tubing resistance for strengthening primarily the vastus medialis.

Figure 21-32. Slide board exercises are used in side-to-side training. The “squat” position should be emphasized.

Figure 21-34. StairMaster (Core Health & Fitness) stepping machine allows the patient to maintain constant contact with the step. (Reprinted with permission from StairMaster.)

Figure 21-35. Stationary bicycling is good for regaining ROM, with seat adjusted to the appropriate height, and also for maintaining cardiorespiratory endurance. (Reprinted with permission from Smooth Fitness and Health.)

Plyometric Exercises

Figure 21-36. Box jumps. Emphasize proper jump-loading technique.

Figure 21-38. Rope skipping is a plyometric exercise that is also good for improving cardiorespiratory endurance.

Isokinetic Exercises

Figure 21-39. Knee extension set up to strengthen the quadriceps concentrically and/or eccentrically. (Reprinted with permission from Biodex Medical Systems.)

Figure 21-40. Knee flexion set up to strengthen the hamstrings concentrically and/or eccentrically. (Reprinted with permission from Biodex Medical Systems.)

Figure 21-42. Biodex manufactures an isokinetic closed chain exercise device. (Reprinted with permission from Biodex Medical Systems.)

Exercises to Reestablish Neuromuscular Control

Figure 21-43. Biomechanical Ankle Platform System (BAPS) board (Spectrum Therapy Products) exercise. (A) Standing. (B) Sitting.

Figure 21-44. Mini-tramp provides an unstable base of support to which other functional plyometric activities may be added.

Figure 21-46. Biofeedback units can be used to help the patient learn how to fire a specific muscle or muscle group.

Figure 21-47. The athletic trainer can emphasize good technique with the aid of a phone or tablet.

Figure 21-48. The single-leg Shark Skill Test is a useful exercise for functional neuromuscular training.

Figure 21-50. Running progression exercises demonstrating proper running technique should include directional changes and pivoting and cutting.

To effectively alleviate lost motion, the cause of the limitation must be identified. An experienced athletic trainer can detect soft tissue resistance to motion by the quality of the feel of the resistance at the end of the range. Muscular resistance, which restricts normal physiological movement, has a firm end-feel and can best be treated by using proprioceptive neuromuscular facilitation (PNF) stretching techniques in combination with appropriate therapeutic modalities (heat, ice, electrical stimulation, etc).147

Strengthening Exercises

A primary goal in knee rehabilitation is the return of normal strength to the musculature surrounding the knee. Along with the return of muscular strength, it is also important to improve muscular endurance and power.¹⁵¹

It is critically important to understand that strength will be gained only if the muscle is subjected to overload. However, it is also essential to remember that healing tissues can be further damaged by overloading the injured structure too aggressively. Especially during the early phases of rehabilitation, muscular overload needs to be carefully applied to protect the damaged structures. The recovering knee needs protection, and the high-resistance, low-repetition program designed to strengthen a healthy knee can compromise the integrity of the injured knee.111 The strengthening phase of rehabilitation must be gently progressive and will generally progress from isometric to isotonic to isokinetic to plyometric to functional exercise.

For years, open kinetic chain (OKC) exercises were the treatment of choice. However, more recently, CKC exercises have been widely used and recommended in the rehabilitation of the injured knee. CKC exercises may be safely introduced early in the rehabilitation process for virtually all types of knee injury.^48,59,178 CKC activities may involve isometric, isotonic, plyometric, and even isokinetic techniques. For years, there has been debate over using OKC vs CKC exercises for knee rehabilitation, especially with regard to ACL postsurgical rehabilitation.^162,177 Several biomechanical investigations have demonstrated that OKC exercises increase anterior tibial shear forces during isokinetic knee extension exercises; in contrast, CKC squat exercises decrease force production.¹⁰⁶ Research on knee muscle activity while performing OKC and CKC exercises has shown that, overall, OKC exercises generate more rectus femoris activity and CKC exercises more vastus medialis and lateralis activity.⁵⁰ This suggests that OKC exercises may be better for patients with isolated rectus femoris weakness, and CKC exercise may be better for vasti musculature strengthening, particularly pathologies involving the patellofemoral joint. Tibiofemoral compressive forces also were reported to be greater in CKC exercises than in OKC exercises, with the squat producing the most compressive force. Another biomechanical investigation¹⁰⁶ also supports these data and has shown that CKC exercises increase compressive forces and cocontraction, whereas OKC exercises at the same angles increase shear force and provide less cocontraction.

Current research has looked at both the force and the strain on the cruciate ligaments during common rehabilitation exercises. An investigation on ACL strain in vivo indicated increased ACL strain during CKC squat from 45 degrees to full extension. OKC knee extension demonstrated a similar pattern, producing ACL strain between 30 degrees and full extension.^15,16 Exercises producing the lowest ACL strain include mostly hamstring activity, quadriceps contraction at knee angles greater than 60 degrees, and isotonic knee flexionextension angles between 35 and 90 degrees.¹⁵ Patellofemoral force during isometric knee extension has been shown to be greatest near full extension. However, during dynamic OKC knee extension, maximum patellofemoral force occurs with 60 to 80 degrees of knee flexion.⁵⁰ This information suggests that OKC dynamic knee extension exercises should be done between 45 to 95 degrees and CKC should be done between 0 to 45 degrees due to optimal patellofemoral contact in these ranges.^25,75,164

CKC exercises may be best for preparing a patient for competition when dynamic stability and functional movement technique are vital to injury prevention. However, specific isolated contractions of certain muscles or muscle groups may demand the use of specific OKC muscle-strengthening exercises. Clinicians should take into consideration the most current biomechanical data to establish the appropriate exercise protocols for various knee ailments and stages of rehabilitation.

Joint Mobilization Techniques

Joint capsule or ligamentous contractures have a leathery end-feel and might not respond to conventional simple passive, active-assisted, and active motion exercises. These contractures can limit the accessory motions of the joint, and until the accessory motions are restored, conventional exercises will not produce positive results. Accessory motions in the knee joint must occur between the patella and femur, the femur and tibia, and the tibia and fibula. Restriction in any or all of these accessory motions must be addressed early in the rehabilitation program.

Mobilization of a knee that is restricted by soft tissue constraints may be accomplished by specifically applying graded oscillations to the restricted soft tissue as discussed in Chapter 13 (see Figures 13-55 through 13-61). In doing so, the athletic trainer is addressing a specific limiting structure rather than assaulting the entire joint with a “crank til you cry” technique. After the release of the soft tissue contracture, accessory motion should improve, and so should physiological motion.

REHABILITATION TECHNIQUES FOR LIGAMENTOUS AND MENISCAL INJURIES

Medial Collateral Ligament Sprain

Pathomechanics

The MCL is the most commonly injured ligament in the knee.¹²⁴ About 65% of MCL sprains occur at the proximal insertion site on the femur. Individuals with proximal injuries tend to have more stiffness but less residual laxity than those with injuries nearer the tibial insertion. Tears of the medial meniscus are occasionally associated with grades 1 and 2 MCL sprains but almost never occur with grade 3 sprains.

Diagnosis of MCL sprains can usually be made by physical evaluation and do not generally require magnetic resonance imaging (MRI). The grade of ligament injury is usually determined by the amount of joint laxity. In a grade 1 sprain, the MCL is tender due to microtears but has no increased laxity, and there is a firm end point. A grade 2 sprain involves an incomplete tear with some increased laxity with valgus stress at 30 degrees of flexion and minimal laxity in full extension, yet there is still a firm end point. There is tenderness to palpation, hemorrhage, and pain on valgus stress test. A grade 3 sprain is a complete tear with significant laxity on valgus stress in full extension. No end point is evident, and pain is generally less than with grade 1 or 2. Significant laxity with valgus stress testing in full extension indicates injury to the medial joint capsule and to the cruciate ligaments.⁸⁵

Injury Mechanism

An MCL sprain almost always occurs with contact from a laterally applied valgus force to the knee that is sufficient to exceed the strength of the ligament. This is especially true with grade 3 sprains. Very rarely, an MCL sprain can occur with noncontact and result in an isolated MCL tear. It has also been suggested that the majority of grade 2 sprains occur through indirect rotational forces associated with valgus movement of the knee.¹⁷⁹ The patient will usually explain that the knee was hit on the lateral side with the foot planted, and that there was immediate pain on the medial side of the knee that felt more like a “pulling” or “tearing” than a “pop.” Swelling occurs immediately, and some ecchymosis likely will appear over the site of injury within 3 days.

Rehabilitation Concerns

Since the early 1990s, the treatment of MCL sprains has changed considerably. Typically grade 3 MCL sprains were treated surgically to repair the torn ligament and then immobilized for 6 weeks. However, several studies have demonstrated that treating patients with isolated MCL sprains nonoperatively with immobilization is as effective as treating them surgically, regardless of the grade of injury, the age of the patient, or the activity level.⁸⁴ This is especially true with isolated MCL tears where the ACL is intact.¹⁷⁶ Patients with a combined MCL–ACL injury will most likely have an ACL reconstruction without MCL repair, and this procedure appears to provide sufficient functional stability.⁸⁵ Three conditions must be met for healing to occur at the MCL: (1) the ligament fibers must remain in continuity or within a well-vascularized soft tissue bed, (2) there must be enough stress to stimulate and direct the healing process, and (3) there must be protection from harmful stresses.¹⁷⁹

With grades 2 and 3 sprains, there will be some residual laxity because the ligament has been stretched, but this does not seem to have much effect on knee function. Patients with grades 1 and 2 sprains may be treated symptomatically and may be fully weightbearing as soon as tolerated. It is possible that a patient with a grade 1 and occasionally even a grade 2 sprain can continue to play. With grade 3 sprains, the patient should not be allowed to play, and a rehabilitative brace should be worn for 4 to 6 weeks set from 0 to 90 degrees to control valgus stress (Figure 21-53).

Rehabilitation Progression

Initially, cold, compression, elevation, and electrical stimulation can be used to control swelling, inflammation, and pain. It may be necessary to have the patient on crutches initially, progressing to full weightbearing as soon as tolerated. The patient should use crutches until (1) full extension without an extension lag can be demonstrated, and (2) the patient can walk normally without gait deviation. For patient comfort, a knee immobilizer may be worn for a few days to a week following injury with grade 2 sprains requiring 7 to 14 days in either an immobilizer or a brace.

The patient with a grade 1 sprain can, on the second day following injury, begin quad sets (Figure 21-20) and straight-leg raising (Figure 21-21). Early pain-free ROM exercises should be incorporated with grade 1 sprains, whereas grade 2 sprains may require 4 to 5 days for inflammation to subside. With grades 1 and 2 sprains, the patient may begin knee slides on a treatment table (Figure 21-3), wall slides (Figure 21-5), active-assisted slides (Figure 21-4 and 21-6), or riding an exercise bike with the seat adjusted to the appropriate height to permit as much knee flexion as can be tolerated (Figure 21-35). As pain subsides and ROM improves, the patient may incorporate isotonic open chain flexion and extension exercises (Figures 21-21 and 21-23), but the patient should concentrate on closed chain strengthening exercises, as tolerated, throughout the rehabilitation process (Figures 21-25 through 21-35). Functional PNF patterns stressing tibial rotation should be incorporated for strengthening, with resistance increasing as the patient becomes stronger (see Figures 14-14 through 14-21). As strength improves, the patient should engage in plyometric exercises (Figures 21-36 through 21-38) and functional activities to enhance the dynamic stability of the knee (see Chapter 16). With a grade 1 sprain, the patient should be able to return to full activity in 3 to 5 weeks.

With a grade 3 sprain, the patient will be in a brace for 2 to 3 weeks with the brace locked from 0 to 45 degrees, and at 0 to 90 degrees for another 2 or 3 weeks, during which time isometric quad sets and straight-leg raise strengthening exercises may be performed as tolerated.¹⁷⁹ The patient should remain nonweightbearing with crutches for 3 weeks. The strengthening program should progress as with grades 1 and 2 sprains, with return to activity at about 3 months.^29,150

Criteria for Return

The patient may return to activity when (1) he or she has regained full ROM, (2) he or she has equal bilateral strength in knee flexion and extension, (3) there is no tenderness, and (4) he or she can successfully complete functional performance tests such as hopping, shuttle runs, carioca, and cocontraction tests.

Lateral Collateral Ligament Sprain

Pathomechanics

Fortunately, the lateral aspect of the knee is well supported by secondary stabilizers. Isolated injury to the lateral collateral ligament (LCL) is rare in athletics, and when it does occur it is critical to rule out other ligamentous injuries.⁹² Most LCL sprains in the athletic population result from a stress placed on the lateral aspect of the knee. Isolated sprain of the LCL is the least common of all knee ligament sprains.¹²⁴ LCL sprains result in disruption at the fibular head either with or without avulsion in about 75% of cases, with 20% occurring at the femur and only 5% as mid-substance tears.¹⁶⁸ It is not uncommon to see associated injuries of the peroneal nerve, because the nerve courses around the head of the fibula. A complete disruption of the LCL often involves injury to the posterolateral joint capsule as well as the PCL and occasionally the ACL.^43,92,111

The extent of laxity determines the severity of the injury. In a grade 1 sprain the LCL is tender due to microtears with some hemorrhage and tenderness to palpation. However, there is no increased laxity and there is a firm end point. A grade 2 sprain involves an incomplete tear with some increased laxity with varus stress at 30 degrees of flexion and minimal laxity in full extension, yet there is still a firm end point. There is tenderness to palpation, hemorrhage, and pain on a varus stress test. A grade 3 sprain is a complete tear with significant laxity on varus stress in 30 degrees of flexion and in full extension compared to the opposite knee. No end point is evident, and pain is generally less than with grades 1 or 2. Significant laxity with varus stress testing in full extension indicates injury to the posterolateral joint capsule, the PCL, and perhaps the ACL.

Injury Mechanism

An isolated LCL injury is almost always the result of a varus stress applied to the medial aspect of the knee. Occasionally a varus stress may occur during weightbearing when weight is shifted away from the side of injury, creating stress on the lateral structures.89 Patients who sustain an LCL sprain will report that they heard or felt a “pop” and that there was immediate lateral pain. Swelling will be immediate and extra-articular with no joint effusion unless there is an associated menicus or capsular injury.

Rehabilitation Concerns

Patients with grades 1 and 2 sprains that exhibit stability to varus stress may be treated symptomatically and may be full weightbearing as soon as tolerated. For patient comfort a knee immobilizer may be worn for a few days to a week following injury. However, the use of a brace is not necessary. It is possible that a patient with a grade 1 and occasionally even a grade 2 sprain can continue to play. With grades 2 and 3 sprains, there will be some residual laxity, because the ligament has been stretched. Grade 3 sprains may be managed nonoperatively with bracing for 4 to 6 weeks limited to 0 to 90 degrees of motion. However, grade 3 LCL tears with associated ligamentous injuries that result in rotational instabilities are usually managed by surgical repair or reconstruction. This is certainly the case if the patient has chronic varus laxity and intends to continue participation in athletics, or if there is a displaced avulsion.

Rehabilitation Progression

The rehabilitation progression following LCL sprains should follow the same course as was previously described for MCL sprains. In the case of a grade 3 LCL sprain that involves multiple ligamentous injury with associated instability that is surgically repaired or reconstructed, the patient should be placed in a postoperative brace with partial weightbearing for 4 to 6 weeks. At 6 weeks, a rehabilitation program involving a carefully monitored, gradual, sport-specific functional progression should begin. In general, the patient may return to full activity at about 6 months.⁸⁹

Criteria for Return

The patient may return to activity when (1) he or she has regained full ROM, (2) he or she has equal bilateral strength in knee flexion and extension, and (3) he or she can successfully complete functional performance tests such as hopping, shuttle runs, carioca, and cocontraction tests, as described in Chapter 16.

Anterior Cruciate Ligament Sprain

Pathomechanics

Injury to the anterior cruciate ligament (ACL) can significantly impair normal function of the knee complex. In simple terms, the ACL functions as a primary stabilizer to prevent anterior translation of the tibia on the fixed femur and posterior translation of the femur if the tibia is fixed as in a closed chain. Specific movement patterns directly influence the load and deformational forces on the ACL.^{14,58,59,96,114} Anterior tibial shear force is the primary factor that contributes to increased ACL loading. Knee flexion angle greatly influences ACL loading as quadriceps contractions at low knee flexion angles (0 to 30 degrees) can generate significant anterior tibial shear forces that facilitate high levels of ACL loading.^8,15,44 Isolated knee valgus and tibial rotation also causes ACL loading, but the magnitude of ACL loading is smaller in comparison to isolated anterior tibial shear force.¹¹⁴ However, when knee valgus and tibial rotation are applied in combination with each other or with anterior tibial shear force, the amount of ACL load is greatly magnified.^14,96,114

The risk for ACL injury is greatest in younger individuals (eg, high school and college ages).157 More ACL reconstruction procedures are performed for high school and college-aged persons than for all other age groups combined.^157,185 However, over the past decade, there has been a significant increase in the number of ACL reconstructions in individuals younger than 15 years.^167,186 The rate of ACL injury is typically greater in women than men, with most research indicating that recreational and competitive female athletes injure their ACL 2 to 5 times more than their male counterparts.^{5,6,7,17,49,63,69,87,105,108,109,123} However, because men have greater exposure to sports and recreational activities than women, the absolute number of ACL injuries in men is greater than the absolute number in women in every age group except at age 15 years.¹⁸⁶ This apparent contradiction is, in fact, an established feature of the epidemiology of ACL injury.⁴ Men account for the majority of injuries in the general population, but, when stratified by physical activity (ie, examining specific sports), women are consistently observed to be at higher risk.^{6,7,17,49,63,69,105,109,123}

Tears of the ACL occur in the mid-substance of the ligament about 75% of the time, with 20% of the tears at the femur and 5% at the tibia.¹¹⁴ As with MCL and LCL sprains, the severity of the injury is indicated by the degree of laxity or instability. A grade 1 sprain of the ACL results in partial microtears with some hemorrhage, but there is no increased laxity, and there is a firm end point. A grade 2 sprain involves an incomplete tear with hemorrhage, some loss of function, and increased anterior translation, yet there is still a firm end point. A grade 2 sprain is painful, and pain increases with Lachman’s and anterior drawer stress tests.

A grade 3 sprain is a complete tear with significant laxity with Lachman’s and anterior drawer stress tests. There is also rotational instability as indicated by a positive pivot shift. No end point is evident. The patient will most often report feeling and hearing a “pop” and a feeling that the knee “gave out.” There is significant pain initially, but pain decreases substantially within several minutes. With a complete ACL tear, insignificant hemarthrosis occurs within 1 to 2 hours.

The term anterior cruciate deficient knee refers to a grade 3 sprain in which there is a complete tear of the ACL. It is generally accepted that a torn ACL will not heal.¹⁶³ An ACL-deficient knee will exhibit rotational instability that may eventually cause functional disability in the patient. Additionally, rotational instability can lead to tears of the meniscus and subsequent degenerative changes in the joint.

Injury Mechanism

The ACL can be injured in several different ways, but noncontact injury mechanisms are most common. There has been considerable discussion on the specific mechanisms that are responsible for injury to the ACL.⁶⁶ To date there is no agreement on one single injury mechanism. However, there is agreement that the ACL may be injured either by direct contact or by a noncontact mechanism. Noncontact mechanisms are about 80% more likely to cause an ACL injury.¹⁰¹

It has become clear that a noncontact injury involves a combination of multiple plane forces collectively acting on the knee joint.^21,155 Most typically, the athlete is decelerating from a jump or forward running.^51,74,134 The foot contacts the ground with the heel, or in a flat-foot position, with little plantar flexion. Weightbearing creates an axial force with the knee near full extension and abducted or in knee valgus.²¹ The axial and valgus forces in combination with a contraction of the quadriceps group produce both an anterior shear and an internal rotation subluxation of the lateral tibia on the femur.¹⁶⁰ This position imposes a substantial strain on the ACL, thus increasing its risk for injury. It should be added that while internal rotation creates greater loading forces on the ACL, external rotation has also produced tears of the ACL.¹⁶⁰

Most recently it has become apparent the position of the hips also has a substantial impact on the incidence of ACL injury.⁵³ It appears that if the hip is adducted relative to the pelvis, the chances of ACL injury are significantly increased. Additionally, in ACL injuries the pelvis on the opposite (nonweightbearing) side drops into a Trendelenburg position, thus further increasing hip adduction on the weight-bearing side and forcing the knee into a more valgus position, increasing the chance of ACL injury even further.35,53 Frank et al described an increase in knee varus internal moment, which is an external knee valgus moment. He describes an external knee valgus moment being associated with a valgus angulation or appearance.⁵³

In a contact injury, the athlete is decelerating and usually changing directions. The foot is planted on the ground with the knee abducted. There is contact from another athlete, most often from lateral and posterior directions, that forces the knee into a valgus and internally rotated position with anterior shear. Once again, in this position, the ACL is at risk for injury. A tear of the ACL and MCL, and possibly a detachment of the medial meniscus, was originally described by O’Donohue as the unhappy triad.¹³⁰

Anterior Cruciate Ligament Injury Risk Factors

Numerous risk factors for ACL injury have been presented in the literature.^{6,69,70,74,80,88,98} Motivated by concern for the high incidence of ACL injuries occurring in 15- to 25-year-old patients, the International Olympic Committee put forth a consensus statement highlighting what is currently known regarding the increased incidence of noncontact ACL injuries in female athletes. The consensus of the Hunt Valley Conference was that ACL risk factors are multifactorial, with 4 distinct areas of risk factors: external, internal, hormonal, and biomechanical.⁶⁶

EXTERNAL RISK FACTORS

The external risk factors include type of competition (game vs practice), footwear and playing surface, protective equipment, and meteorological conditions. At present, there is no evidence to indicate that these factors influence noncontact ACL injury risk, but additional research is needed in this area.

INTERNAL RISK FACTORS

The internal risk factors include anatomical factors. The conference decided that there was a great amount of information on femoral intercondylar notch size, ACL size, and lower extremity anatomic alignment (eg, Q-angle, pronation, tibial torsion) as they related to ACL injury. However, because of the difficulty of obtaining valid and reliable measurements, no consensus on their role in ACL injury could be reached.

HORMONAL RISK FACTORS

A systematic review of the literature investigating the effects of menstrual cycle on ACL injury risk suggests an increased risk of injury during the ovulatory phase.⁷⁴ A summary of published data supports an increase in knee joint laxity during this phase and hence an increased risk of ACL injury. However, more research is still needed in this area to provide stronger evidence for hormonal risk factors for ACL injury.⁷³

BIOMECHANICAL RISK FACTORS

The knee is only one part of the kinetic chain; therefore, the roles of the trunk, hip, and ankle may have importance to ACL injury risk. Common biomechanical factors in many ACL injuries include impact on the foot rather than the toes during landing or when changing directions while running, awkward body movements, and biomechanical perturbations prior to injury.¹⁵⁵ The common at-risk situation for noncontact ACL injuries appears to be deceleration, which occurs when the patient pivots, changes direction, or lands from a jump. The group also noted that neuromuscular factors (eg, joint stiffness, muscle activation latencies, muscle recruitment patterns) are important contributors to the increased risk for ACL injuries in women and appear to be the most important reason for the differing ACL injury rates between men and women.^82,155 The final factor stated was that strong quadriceps activation during eccentric contraction was considered to be a major factor in ACL injury.¹⁵⁵

Anterior Cruciate Ligament Injury Prevention Programs: Prehabilitation

Over the years a number of studies have suggested that ACL injuries are to a large extent preventable.^67,72,99,132 With the majority of ACL injuries being noncontact or indirect contact in nature, injury prevention programs can be effective in correcting faulty biomechanics and in turn reducing the risk of ACL injury.¹³⁶ In a recent position statement published by the National Athletic Trainers’ Association, a preventive training program is recommended for all athletes, most notably those participating in sports that involve landing, cutting, and decelerations.135 Specifically in women between the ages of 13 and 24 years, injury prevention programs have been reported to reduce the risk of ACL injury.^62,102,175 Additionally, in one high quality study, men were found to have a reduction in ACL injury risk following completion of an injury prevention program.¹⁶¹

The position statement also recommends the use of a multicomponent program that includes a variety of exercises and movement feedback.¹³⁵ In a recent meta-analyses, a multicomponent program including strength, balance, plyometric, and proximal neuromuscular control exercises was found to be more effective in reducing ACL injuries than a single-component program.¹⁶⁶ Based on these findings the inclusion of preventive training exercises from at least 3 of the following categories is recommended when implementing an injury prevention program: strength, plyometrics, agility, flexibility, and balance (Figures 21-24 through 21-50). The injury prevention program should also include feedback on movement technique and quality. Previous studies support a change in kinematics and landing forces with the use of movement feedback and a focus on movement quality.^{83,125,141,145,146} No direct link has been made between changes in landing forces and kinematics and a reduction in ACL injury risk; however, these changes likely reduce strain placed on the ACL during dynamic activities.

Preventive training session frequency and duration are 2 important factors to consider when implementing a program. The current evidence supports 2 to 3 training sessions per week to reduce the risk of ACL injuries.¹³⁵ Also, to ensure the preventive program is effective in modifying neuromuscular risk factors for ACL injury and participants can retain these changes in the long term, it is recommended that programs begin early in the preseason and continue into the in-season. The athletic trainer should monitor compliance with completion of the training sessions, as a higher compliance is reported to lead to a greater reduction in ACL injury risk.¹⁶⁷

More high-quality studies are needed to better understand the most important components to be included in an ACL injury prevention program. Additionally, more research is needed to better understand the efficacy of preventive programs in men. However, based on the current evidence, the implementation of a multicomponent program in individuals participating in sport can reduce the risk of ACL injury.¹³⁵

Rehabilitation Concerns

After the diagnosis of injury to the ACL, the patient, the physician, the athletic trainer, and the patient’s family are faced with various treatment options. The conservative approach is to allow the acute phase of the injury to pass and to then implement a vigorous rehabilitation program. If it becomes apparent that normal function cannot be recovered with rehabilitation, and if the knee remains unstable even with normal strengthening and hamstring retraining, then reconstructive surgery is considered. For a sedentary individual, this approach may be acceptable, but most patients prefer a more aggressive approach.

The older and more sedentary the individual, the less appropriate a reconstruction is. This individual may not have the inclination or the time for an extensive rehabilitation program and may not be greatly inconvenienced by some degree of knee instability. Conversely, the ideal patient is a young, motivated, and skilled patient who is willing to make the personal sacrifices necessary to successfully complete the rehabilitation process. Wilk and Andrews state that any active individual with a goal of returning to stressful pivoting activities should undergo surgical ACL reconstruction.¹⁷⁷ Thus, successful surgical repair/reconstruction of the ACL-deficient knee largely depends upon patient selection.⁹⁰ The following would be indications for deciding to surgically repair/reconstruct the injured knee:

• The ACL-injured individual is highly active
  
• The injured person is unwilling to change his or her active lifestyle
  
• There is rotational instability and a feeling of the knee “giving way” in normal activities
  
• There is injury to other ligaments and/or the menisci
  
• There are recurrent effusions
  
• There is failure at rehabilitation and instability after 6 months of intensive rehabilitation90
  
• Surgery is necessary to prevent the early onset of degenerative changes within the knee⁹²

In the case of a partially torn ligament, the medical community is split on a treatment approach. Some feel that a partially damaged ACL is incompetent, and the knee should be viewed as if the ligament were completely gone. Others prefer a prolonged initial period of immobilization and limited motion, hoping that the ligament will heal and remain functional. Decisions to treat a patient nonoperatively should be based on the individual’s preinjury status and willingness to engage only in activities such as jogging, swimming, or cycling that will not place the knee at high risk.¹²⁷ This is clearly a case where the patient may wisely seek several opinions before choosing the treatment course.

The most widely accepted opinion seems to be that when more than one major ligament is disrupted and there is functional disability, surgery is indicated. The surgical approach to ACL pathology is either repair or reconstruction. With a surgical repair, the damaged ligament is sutured if the tear is in the midsubstance of the ligament or the bony fragment is reattached in the case of an avulsion injury. However, it is generally felt that direct repair of an isolated ACL tear will tend to have a poor result.⁴ In the case of suturing, the repair may be augmented with an internal splint or an extra-articular reconstruction, which seems to be more successful than a direct repair.¹⁵⁶

Surgical reconstruction is performed using either an extra-articular or an intra-articular technique. An extra-articular reconstruction involves taking a structure that lies outside of the joint capsule and moving it so that it can affect the mechanics of the knee in a manner that mimics normal ACL function. The iliotibial band is the most commonly used structure. This procedure is effective in reducing the pivot shift phenomena that is found in anterolateral rotational instability but cannot match the normal biomechanics of the ACL.⁹⁰ Isolated extra-articular reconstructions can be effective in patients with mild to moderate instability. Also, it may be the treatment of choice in patients who cannot afford the commitment of time and resources for an intra-articular reconstruction.⁹⁰ The rehabilitation after an extra-articular reconstruction is aggressive and permits an earlier return to functional activities, but as an isolated procedure, it is not recommended for individuals who participate in a high level of activity.

Intra-articular reconstruction involves placing a structure within the knee that will roughly follow the course of the ACL and will functionally replace the ACL. Techniques for reconstructive surgery for the ACL continue to evolve, and the choice of a particular technique is most often based on the surgeon’s preference and expertise.^30,177 Currently there appear to be at least 4 primary surgical techniques that use autografts for reconstructing a torn ACL.

A bone–patellar tendon–bone graft uses the central one-third of the patellar tendon. Since the mid 1980s it has been the gold standard choice for the majority of surgeons because of an excellent surgical outcome success rate of 90% to 95%.^30,34,177

A hamstring tendon graft uses the tendons of either the semitendinosus, the gracilis, or both.³⁰ As graft fixation techniques and hardware have improved, so has the popularity of this technique. Although it is generally considered to be a more technically difficult surgery, it requires a smaller incision, and there is less anterior pain and quadriceps atrophy than with a patellar tendon graft. However, a hamstring tendon graft technique involves soft tissue to bone healing, which occurs at a significantly slower rate than bone to bone healing following a patellar tendon graft. Currently, there does not appear to be any strong evidence to suggest that either technique is superior in terms of outcomes.

A third, less widely used, technique uses a graft from the quadriceps tendon just above the patella that has bone on one end and soft tissue on the other. There seems to be less chance of patellar tendinitis and kneeling pain associated with quadriceps tendon grafts. They are often used for revision ACL surgeries.

Allografts can use patellar, hamstring, or Achilles tendons and are used more often in revisions when an autograft has already been used.91 But most surgeons prefer to use an autograft for an initial reconstruction. Allografts take longer to heal than autografts, but recovery from surgery is quicker because of less pain and tissue healing from not having to harvest the patient’s own tissue. The main problems with allografts are disease transmission and rejection of the tissue. It has been demonstrated that at 6 months post surgery, allografts show a prolonged inflammatory response and a more significant decrease in their structural properties.⁹¹ Rehabilitation following an allograft reconstruction should be less aggressive than with an autograft reconstruction.⁹¹

Procedures that use synthetic replacements have generally not produced favorable results.

Surgical technique is crucial to a successful outcome. Improper placement of the tendon graft by only a few millimeters can prevent the return of normal motion.⁷¹

In cases where there is reconstruction of the ACL along with a repair of a torn meniscus, the time required for rehabilitation will be slightly longer. This will be discussed in detail in the section on meniscal injury.

Rehabilitation Progression

NONOPERATIVE REHABILITATION

If the ACL-deficient knee is to be treated nonoperatively, it is critical to rule out any other existing problems (torn meniscus, loose bodies, etc) and correct those problems before proceeding with rehabilitation.¹²⁷ Initial treatment should involve controlling swelling, pain, and inflammation through the use of cold, compression, elevation, and electrical stimulation. If necessary, the knee can be placed in an immobilizer (Figure 21-52) for the first few days for comfort and minimal protection, with the patient ambulating on crutches until he or she regains full extension and can walk without an extension lag. The patient can begin immediately following injury with quad sets (Figure 21-20) and straight-leg raising (Figure 21-21) to regain motor control and minimize atrophy. Early pain-free ROM exercises include using knee slides on a treatment table (Figure 21-3), wall slides (Figure 21-5), active-assisted slides (Figures 21-4 and 21-6), or riding an exercise bike with the seat adjusted to the appropriate height to permit as much knee flexion as can be tolerated (Figure 21-35).

As pain subsides and ROM improves, the patient may incorporate isotonic open chain flexion and extension exercises (Figures 21-22 and 21-23). With OKC strengthening exercises, it has been recommended that extension be restricted initially to 0 to 45 degrees for as long as 8 to 12 weeks (6 to 9 weeks being a minimum) to minimize stress on the ACL.¹²⁷ Strengthening exercises should be emphasized for both the hamstrings and the gastrocnemius muscles (Figure 21-24), which act to translate the tibia posteriorly, minimizing anterior translation. CKC strengthening exercises (Figures 21-25 through 21-35) are thought to be safer because they minimize anterior translation of the tibia. CKC exercises are used to regain neuromuscular control by enhancing dynamic stabilization through cocontraction of the hamstrings and quadriceps (Figures 21-43 through 21-46). CKC exercises also minimize the possibility of developing patellofemoral pain. A goal of these strengthening exercises should be to achieve a quadriceps/hamstring strength ratio of 1 to 1.

It is important to incorporate PNF strengthening patterns that stress tibial rotation (see Figures 14-14 through 14-21). These manually resisted PNF patterns are essentially the only way to concentrate on strengthening the rotational component of knee motion, which is essential to normal function of the knee. Unfortunately, many of the more widely known and used rehabilitation protocols fail to address this critical rotational component.

Perturbation training may be particularly important for those with an ACL-deficient knee. Perturbation training is a type of neuromuscular exercise focused on improving knee stability and involves the manipulation of an unstable support surface while the patient maintains his or her balance.⁸¹ The inclusion of perturbation training should be performed in combination with the other types of exercises described previously to facilitate strength, cardiorespiratory endurance, and agility.

Perturbation training includes 3 conditions: rollerboard, rockerboard, and rollerboard with block. The use of verbal cues such as “keep your knee soft,” “keep your trunk still,” and “relax between perturbations” are commonly employed during perturbation training to direct patients on successful completion of the tasks and further enhance neuromuscular control. The perturbation training program should be progressive in nature. Hurd et al describe the phasic and progressive nature of perturbation training as follows.81 During the early phase of training, the patient should be exposed to perturbations in all directions. The patient is provided minimal verbal cues as he or she explores to develop the appropriate neuromuscular response patterns to the perturbations without creating a rigid cocontraction of knee musculature. During the middle phase, the addition of light sport-specific activity can be employed during perturbation training. During this phase, the patient should develop improved accuracy in using appropriate neuromuscular responses to the applied perturbation intensity, direction, and speed. In the final or late phase of perturbation training, the difficulty of perturbations is enhanced by using sport-specific stances. Focus should be on obtaining accurate, selective muscular responses to the applied perturbations in any of the applied directions and of any intensity magnitude or speed.

The use of functional knee braces for a patient with either a partial ACL tear or an ACL-deficient knee is controversial (Figure 21-51). These braces have not been shown to control translation, especially at functional loads.^18,148 However, there may be some benefit in terms of increased joint position sense, through stimulation of cutaneous sensory receptors, that may enhance both conscious and subconscious awareness of the existing injury.¹⁰⁴

It is incumbent on the athletic trainer to counsel the patient with regard to the precautions that must be exercised when engaging in physical activity with an ACL-deficient knee. Nonoperative treatment is appropriate for an individual who does not plan on engaging in the types of activities that can potentially create stresses that can further damage the supporting structures of that joint. If the patient is not willing to make lifestyle changes relative to those activities, then surgical intervention may be a better treatment alternative.

Clinical Decision-Making Exercise 21-3

A soccer player has suffered an isolated grade 2 sprain of his ACL. At this point, the physician feels that surgery is not required and decides to try to rehabilitate the patient’s knee and have him return to practice. It is likely that when he returns to full activity, the patient will experience some feeling of instability when stopping, starting, and pivoting. What can the athletic trainer recommend to the patient to help him minimize these feelings of instability and to prevent additional injury to the ACL?

SURGICAL RECONSTRUCTION

There is great debate as to the course of rehabilitation following ACL reconstruction. Traditionally, rehabilitation has been conservative, and there are a great number of physicians and athletic trainers who maintain this basic traditional philosophy.138,139 However, at one point, the trend was to be more aggressive in rehabilitation of the reconstructed ACL, primarily as a result of the reports of success by Shelbourne and Nitz.¹⁵⁹ This was referred to as an accelerated protocol. They demonstrated that this program returning the patient to normal function early results in fewer patellofemoral problems, and reduces the number of surgeries to obtain extension, all without compromising stability. The accelerated rehabilitation protocol is not without its detractors. Some clinicians feel that it places too much stress on vulnerable tissues and that there are not sufficient scientific data to justify the protocol.^128,138,177

There is now such a variety of accelerated and nonaccelerated programs that the difference between “traditional” and “accelerated” has been blurred. Depending on the injury, many factors—such as type of patient, time of athletic season—have been driving the rehabilitation process to a greater extent than science-based outcomes. More studies need to be conducted to better predict the ideal rehabilitation protocol, yet individual differences may never allow for a single protocol to be used for all patients.

ACL rehabilitation protocols generally emphasize the following^{45,48,89,138,183,184}:

• Slow progression to regain flexion and extension
  
• Partial- or nonweightbearing postoperatively
  
• Closed chain exercises at 3 to 4 weeks postoperatively
  
• Return to activity at 6 to 9 months

The accelerated protocol emphasizes the following:

• Immediate motion, including full extension
  
• Immediate weightbearing within tolerance
  
• Early closed chain exercise for strengthening and neuromuscular control
  
• Return to activity at 2 months and to competition at 5 to 6 months¹⁵⁹

Preoperative period. Regardless of the various recommended time frames for rehabilitation, the rehabilitative process begins immediately following injury in what has been referred to as the preoperative phase. There is general agreement that surgical reconstruction be delayed until pain, swelling, and inflammation have subsided and ROM, quadriceps muscle control, and a normal gait pattern have been regained during this preoperative phase. This appears to occur at about 2 to 3 weeks post injury.⁴⁵ It also appears that delaying surgery decreases the incidence of postoperative arthrofibrosis.⁴⁸

Postoperative period. Perhaps the single most important rehabilitation consideration postoperatively has to do with the initial strength of the graft and how the graft heals and matures. It has been demonstrated that the tensile strength of a 10-mm central third patellar tendon graft is about 107% of the normal ACL initially, and it has been predicted that the strength is at 57% at 3 months, 56% at 6 months, and 87% at 9 months.¹³⁸ Stress on the graft should be minimized during the period of graft necrosis (6 weeks), revascularization (8 to 16 weeks), and remodeling (16 weeks).¹⁷⁷ Assuming that the surgical technique for reconstruction is technically sound, the graft is at its strongest immediately following surgery, so rehabilitation can be very aggressive early in the process. Also it appears that an aggressive rehabilitation program minimizes complications and maximizes restoration of function following ACL reconstruction.⁸⁹

Figure 21-53. In a rehabilitative brace, the range of movement can be restricted and changed whenever appropriate. (Reprinted with permission from DonJoy.)

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