Chapter 65 Principles of Anterior Cruciate Ligament Rehabilitation

Introduction

Rehabilitation with anterior cruciate ligament (ACL) reconstruction has evolved considerably since the 1970s when intraarticular ACL reconstructions were first being performed. We have evolved from using casts on the leg for 6 weeks after surgery to no immobilization at all, from restricting weight bearing to encouraging weight bearing, from limiting range of motion to foster stability to emphasizing exercises to achieve full knee extension and flexion, and from restricting the return to sports until 1 year after to surgery to allowing participation in sports as soon as the patient is able to do so. We made this progression by systematically evaluating how different factors about surgery and what patients actually did during rehabilitation affected our patients’ results, and then we made improvements in our rehabilitation techniques to improve the overall outcome.

Proper perioperative rehabilitation with ACL reconstruction is just as important as proper graft placement with surgery. We suggest that the orthopaedic surgeon needs to be intimately involved with the rehabilitation process to provide a consistent and effective program for patients to follow. It is most helpful to develop a close relationship with one or two physical therapists who will treat all the physician’s patients. The repetition of seeing many patients after ACL reconstruction done by the same surgeon allows the physical therapist to become familiar with what condition the knee will be in after surgery, to learn the best way to treat any problems that arise, and to develop a rehabilitation program that prevents postoperative complications. Furthermore, when the surgeon has a good working relationship with a physical therapist, the physical therapist can do preoperative rehabilitation and testing to let the physician know when a patient is physically ready for surgery.

The main complication after ACL reconstruction has been the limitation of knee range of motion or arthrofibrosis. Arthrofibrosis is defined as abnormal proliferation of fibrous tissue in and around a joint that can lead to loss of motion, pain, and muscle weakness. It is believed that arthrofibrosis is more common with the patellar tendon autograft, but it is found with all graft sources.¹^–⁴ We believe that improper perioperative rehabilitation, not the graft source itself, is the culprit for causing arthrofibrosis and that it can be avoided with all ACL reconstruction surgery if the proper rehabilitation is applied before and after surgery.

Regardless of surgical technique or graft source, the goal for all patients after ACL reconstruction is to have a normal knee—one that has full range of motion, strength, and function. If the ACL reconstructed knee feels different than the contralateral normal knee, then the patient can function only at the level of the worst leg. Therefore symmetry between legs is the ultimate goal, not just ACL stability.

People have symmetrical knees that are unique to the individual. In evaluating full range of motion, an important consideration is that 99% of women and 95% of men show some degree of hyperextension in their knees with averages of 5 and 6 degrees, respectively.⁵ Current data analysis of results of ACL reconstruction shows that any loss of knee extension or flexion is the major factor related to lower subjective scores at 10 to 20 years after surgery. Even the loss of 3 to 5 degrees of extension compared with the opposite knee can result in lower postoperative subjective scores.⁶ Thus the definition of full range of motion must depend on symmetry between the knees rather than the conventional practice of gauging knee motion against a fixed standard.

To measure knee extension, the heel of the foot should be placed on a bolster so that the knee can fall into hyperextension (Fig. 65-1). The motion should be compared with the opposite normal knee. To get a kinetic feel for how easily the knee moves into hyperextension, the examiner can evaluate hyperextension by placing one hand above the knee to fix the femur and placing the other hand on the patient’s foot to lift the heel off the table (Fig. 65-2). Knee flexion can be measured by having the patient pull the heels toward the buttocks. When the knee is normal, the patient can kneel and sit back on the heels comfortably (Fig. 65-3). These evaluation tools should be used to determine whether the patient has full symmetrical knee motion.

Fig. 65-1 The heel of the foot should be placed on a bolster so that the knee can fall into hyperextension. A goniometer is used to measure extension.

Fig. 65-2 The examiner can get a kinetic feel for how easily the knee moves into hyperextension by placing one hand above the knee to fix the femur and placing the other hand on the patient’s foot to lift the heel off the table.

Fig. 65-3 Patients who have normal knee flexion can sit back on their heels without having any tilt in the hips.

With the knowledge that full range of motion is essential—not only for athletes to function at a high level, but also for less active patients to be able to comfortably perform everyday activities such as squatting, kneeling, ascending, and descending stairs—we have designed our perioperative rehabilitation program with the principal goal of achieving postoperative symmetry between knees. The program begins at the time of the initial evaluation to include preoperative rehabilitation through the time the patient is fully recovered and has returned to full activities. Patients follow a cascade of events that has few time constraints but must be followed sequentially to be most effective.

Preoperative Rehabilitation

After an acute ACL injury, the knee almost always develops a hemarthrosis. The hemarthrosis and inflammatory reaction cause the knee to lose range of motion and the leg to lose some quadriceps muscle strength. Patients typically walk with a bent-knee gait and require crutch assistance. Preoperative rehabilitation is divided into two areas of emphasis. First, physically the patient should regain normal knee range of motion with very little swelling and should be able to walk with a normal gait. Secondly, the patient should be prepared mentally for the operative procedure and subsequent rehabilitation.

The initial emphasis after an acute injury to the ACL is to control and then decrease the amount of swelling and pain. We use the knee Cryo/Cuff (Aircast, Summit, NJ), which combines cold with compression to reduce the hemarthrosis. The second goal of rehabilitation after an acute ACL injury is to restore normal knee range of motion, including full hyperextension equal to the noninjured knee. Obtaining full range of motion before surgery reduces the likelihood of motion problems postoperatively.⁷^–⁹

A habit of performing full hyperextension exercises is important to develop preoperatively so that the exercises are easily a part of a daily routine after surgery. Several exercises and modalities are used to gain full normal hyperextension. Towel stretches are performed as a passive self-mobilization technique using a towel looped around the midfoot. The towel ends are held in one hand while the other hand is used to press and hold the thigh to the table. The towel is used to lift the heel of the affected lower extremity to end-range hyperextension by pulling the end of the towel upward toward the shoulder, where it is held for a count of 5 seconds, and then the heel is lowered back to the table (Fig. 65-4). For patients who have decreased quadriceps muscle control, an active heel-lift exercise can easily be added to the towel stretch. The active heel lift is accomplished by contracting the quadriceps musculature after the towel stretch is performed, trying to keep the heel of the affected leg elevated without using the towel to hold it in the air. Initially after injury, patients often display some degree of quadriceps muscle inhibition, making a normal gait pattern difficult. It is important that the patient continue to try to actively elevate the heel to the height of the passive stretch.

Fig. 65-4 Towel stretch exercise. The towel is used to lift the heel of the affected lower extremity to end-range hyperextension by pulling the end of the towel upward toward the shoulder.

Passive extension in a seated position can be obtained by performing a heel prop on a towel or other type of bolster. The bolster should be high enough to elevate both the calf and the thigh of the affected extremity off the level of the table. A small weight can be added to the proximal tibia to facilitate full extension.

The standing extension habit focuses on the patient’s ability to stand on the affected leg with the knee in a full hyperextended position. It is normal to stand on one leg with the knee locked into full hyperextension, and following an injury, patients will tend to favor their injured leg and stand on the nonaffected leg. To stand comfortably on one leg, patients must regain full hyperextension to rest on the passive joint structures. Forcing patients to stand on their affected lower extremity ensures that full hyperextension is regained and maintained.

Regaining full knee flexion is achieved through performing wall slide and heel slide exercises. Wall slides are performed while lying supine with both legs extended up the wall. The heel of the injured leg is allowed to slide down the wall so that the knee is put into a flexed position with assistance from the noninjured leg until a stretch is felt in the knee. This is maintained for approximately 10 to 15 seconds; the leg is then extended back to the starting position, where the quadriceps muscle is squeezed and the leg is locked out for 5 seconds, and then the exercise is repeated. Heel slide exercises are started once the patient has at least 90 degrees of flexion. They are performed while in a long sitting position as the patient grasps the ankle of the involved extremity and passively pulls the leg into knee flexion. This is held for 10 to 15 seconds, and then the leg is allowed to fully extend back to a resting position. Patients should be instructed to watch for compensation in the hip during these flexion exercises. It is common for patients to substitute hip retraction in place of knee flexion when first trying to perform these flexion exercises. This should be avoided in order to maximize full flexion of the knee.

Full weight bearing is allowed as tolerated by the patient, but a normal gait pattern must be achieved. Crutches are used to assist ambulation if the patient exhibits an antalgic gait pattern. Once a normal gait pattern is obtained, patients are allowed to ambulate without the use of any assistive device or prophylactic braces. Once the patient has achieved full range of motion, good leg control, and a normal gait with minimal swelling, he or she can begin a low-impact strength and conditioning program until surgery. Appropriate activities include the use of a stationary bicycle, elliptical machine, or stair-stepping machine, along with closed kinetic chain strengthening exercises for the lower extremity such as leg press, hip sled, and step-down exercises. Education on avoidance of high-risk activities that include twisting and rotation of the knee should be emphasized with the patient so that instability episodes prior to surgery can be avoided.

We perform preoperative testing so that we can have objective measures for closely monitoring postoperative progress and to assist the patient in setting performance goals. The testing includes KT-1000 arthrometer testing of anterior translation, isokinetic strength at 180 degrees/sec and 60 degrees/sec, and isometric leg press test. The single leg–hop test is performed on the uninjured leg only. Strength is measured as a percentage of the involved lower extremity against the noninvolved lower extremity. Differences observed between the two lower extremities should be within 25% of each other before surgery when using an ipsilateral patellar tendon graft source. If the differences between the two legs are greater than 25%, a delay in surgery may be recommended so that the patient can work on strengthening the weaker lower extremity. When using a contralateral patellar tendon graft source, strength differences of greater than 25% are allowable as long as the patient has good quadriceps muscle control and normal ambulation. These data are used again postoperatively, starting at 1 month, to compare the athlete’s status with his or her preoperative strength and function.

The overall goal of physical therapy in the preoperative phase is to control and decrease pain and swelling, restore full range of motion, aid in the resumption of a normal gait pattern, and initiate a strengthening program. By accomplishing these goals, the patient will present to the operative room for the reconstructive procedure with a normal-appearing and functioning knee except for the absence of the ACL.

Mental Preparation

The second important factor in the preoperative preparation of an ACL reconstruction procedure is the mental preparation of the patient. Physical therapists follow patients closely and communicate with the surgeon regarding a patient’s mental and physical preparation for surgery, as the success of reconstruction depends on both factors.¹⁰ The physician must explain the nature of the injury to the athlete and family. The patient benefits from a detailed explanation of the operative procedure and the postoperative rehabilitation. The physical therapist should also review with the patient exactly what will be performed in all phases of the postoperative rehabilitation and how each phase of rehabilitation will be accomplished. The patient should approach the reconstruction procedure with a positive mental outlook. A “let’s just get it over with” attitude is not acceptable and can lead to less than superior results, even with perfect surgical and rehabilitation techniques. The patient should arrive in the operating room ready to go with an attitude of looking forward to the reconstructive procedure and with an understanding of the postoperative rehabilitation.