Articular Cartilage Procedures of the Knee
G. Kelley Fitzgerald, PhD, PT and James J. Irrgang, PhD, PT, ATC
Clinical Background
Designing successful rehabilitation programs after articular cartilage surgical procedures requires careful consideration of the healing process and a thorough understanding of the potential stresses applied to articular surfaces during therapeutic exercise. Although it is important to begin early rehabilitation to promote tissue healing and to restore joint motion, muscular strength, and functional capacity, rehabilitation procedures must be applied in a manner that does not interfere with or disrupt the healing articular lesion.
Types of Motion
Evidence from animal studies suggests that early active and passive motion exercises after articular cartilage lesions can enhance the quality of tissue healing, limit the adverse effects of joint immobilization on the remaining healthy articular cartilage, and reduce the risk of adhesions. Complete immobilization is not recommended after surgical procedures that involve the articular cartilage.
However, the application of shear stress while the healing articular lesion is under compression may have adverse effects on the healing process. ROM exercises should be done in a controlled manner to avoid excessive shear loads while the joint is under compression. This can be accomplished by emphasizing passive, active-assisted, and unloaded-active ROM exercises in the early postoperative period (0–6 weeks).
Muscle Strengthening
Muscle performance training is an essential component of postoperative rehabilitation after articular cartilage surgical procedures. Muscles need to be strong enough to assist in absorbing shock and dissipating loads across the joint. The resistance exercise program should be tailored to minimize shear loading across the lesion during the healing period. In general, exercises that have the potential for producing high shear stress coupled with compression, such as closed-chain exercises, should be avoided in the early phases of rehabilitation.
We believe isometric exercises are the safest option for restoring muscle strength during early rehabilitation.
Isometric quadriceps exercises in full knee extension may be effective in preventing or resolving a knee extensor lag, and most articular lesions will not be engaged with the knee in full extension. Isometric exercise at 90 degrees of flexion may also be a safe option because it is unlikely to result in excessive compression or shear loads across most articular cartilage lesions. In addition, it has been shown that isometric quadriceps training at 90 degrees of flexion can result in increased muscle force production at other joint angles. Isometric exercises at angles between 20 and 75 degrees should be used with caution because most articular lesions would be engaged in this arc of motion. If open-chain leg extension exercises are to be used, it is essential that the arc of motion is limited to ranges that do not engage the lesion. This requires effective communication between the surgeon and the therapist regarding ROM limitations for resistive exercises.
Weight-bearing Progression
Progression of weight-bearing and functional activities is a gradual process that begins in the intermediate phase of postoperative rehabilitation. The weight-bearing status after surgery is dependent on the size, nature, and location of the lesion, as well as the surgical procedure that has been used to treat it. Progression of weight-bearing is also dependent on the resolution of joint motion and muscular strength impairments in the early rehabilitation period.
After arthroscopic débridement, patients are usually permitted to bear weight as tolerated with crutches. Weight-bearing can be progressed as long as increased loading does not result in increased pain or effusion. Crutches can be discontinued when the patient has full passive knee extension and at least 100 degrees of knee flexion, can perform an SLR without an extensor lag, and can walk without pain or limp.
When patients have undergone abrasion arthroplasty, microfracture procedure, fixation of an articular cartilage defect, or osteochondral graft, weight-bearing is usually delayed for 6 weeks to allow adequate initial healing of the lesion. Non-weight-bearing or touch-down weight-bearing with crutches is allowed in the immediate postoperative period. In some cases, depending on the location of the lesion or stability of fixation, partial weight-bearing or weight-bearing as tolerated with crutches may be permitted in conjunction with use of a rehabilitation brace locked in full knee extension. Progressive weight-bearing is usually begun 6 weeks after surgery. At this time, fibrocartilage should have begun to fill in the articular defect and an osteochondral graft or articular cartilage fragment should have united with adjacent subchondral bone. Crutches can be discontinued when the patient has full passive knee extension and at least 100 degrees of knee flexion, can perform an SLR without an extensor lag, and can walk without an extensor lag, and can walk without pain or limp. Therapists should monitor patients for increases in pain or effusion during progressive weight-bearing and reduce the progression if these iatrogenic effects arise.
The progression from protected weight-bearing to full weight-bearing can be facilitated by using techniques that gradually increase the load on the knee. Deweighting devices can be used for treadmill ambulation and running. Unloading of body weight by the deweighting device is increased to the point that allows performance of the activity without pain or gait abnormalities. The unloading is then gradually reduced over time until the patient can perform the activity in full weight-bearing without pain. A pool can also be used to unload body weight for ambulation and running activities. These activities can be initiated in shoulder-deep water and then gradually progressed by decreasing the depth of the water.
Once the patient has progressed to pain-free full weight-bearing, a variety of low-impact aerobic activities, such as walking, cycling, and use of step or cross-country ski machines, can be employed to improve local muscular and cardiovascular endurance. Returning to sports activities may not be possible for some patients, depending on the severity of joint damage. These patients should be counseled with respect to appropriate activity modifications. For patients who wish to return to recreational or sports activities, a functional retraining program, involving agility training and sport-specific skill training, should be incorporated into the program. These activities should be delayed until the patient can perform low-impact aerobic activities without recurrent pain or effusion. Agility and sport-specific skill training should be progressed gradually from 50% effort to full effort. The therapist should continue to monitor the patient for changes in pain and effusion as these activities are progressed.
Important Rehabilitation Considerations
The surgeon should include on the physical therapy referral form the type of surgical procedure, the location of the lesion, and restrictions in ROM during exercise. A diagram of the lesion site is also helpful. Therapists must adhere to the surgeon’s ROM limitations so that the lesion is not engaged during exercise.
Unloaded passive or active-assisted ROM exercises should begin as soon as possible after surgery. Closed-chain exercises should be avoided in the first 6 weeks after surgery.
Isometric exercises with the knee in full extension or 90 degrees of flexion should be emphasized for early strength training. Open-chain exercises can be used in arcs of motion that do not engage the lesion.
Protected weight-bearing with the use of crutches, and in some cases, a rehabilitation brace, should be incorporated in the first 6 weeks after surgery. Assistive devices can be discontinued when the patient has full knee extension and 100 degrees of knee flexion, can perform an SLR without an extensor lag, and can walk without pain or limp.
Progression of weight-bearing activities can be made easier by gradually increasing the load on the knee. This can be accomplished with the use of deweighting devices or pool activities. A gradual progression of agility and sport-specific skill training should be completed before the patient is allowed to return to full sports activity.
Rehabilitation Protocol
Our rehabilitation protocol is divided into three phases: early postoperative phase (0–6 weeks), intermediate phase (6–12 weeks), and return to activity phase (12 weeks and beyond). The time frames for these phases are only estimated guidelines. Progression to each phase depends on meeting criteria based on the type of surgical procedure, estimated periods of healing, restoration of joint mobility and strength, and potential recurrence of pain and joint effusion. Individual patients are able to progress at different intervals, and the surgeon and therapist are required to use their clinical judgments in determining when progression should be delayed or can be accelerated.
Trouble-shooting Techniques after Articular Cartilage Procedures
Pain and Effusion with Exercise or Activity Progression
Monitoring of pain and effusion in response to exercise or activity progression is important to maintain a safe and effective rehabilitation process. Pain and effusion in response to exercise may indicate that the articular lesion is being harmed or the intensity of exercise is too rigorous. Therapists should reconsider the ROM restrictions that are being used and perhaps modify them to reestablish pain-free ranges. The frequency and duration of joint mobility exercise or the magnitude of loading during resistance exercises may also have to be reduced.
Recurrent pain and effusion that occur during progression of weight-bearing or functional retraining activities indicate that the joint is not ready to progress to higher levels of activity. Progression of activity may need to be delayed in these circumstances.
Footwear and activity surface-types should also be considered. Patients may need to obtain footwear that provides better cushioning or biomechanical foot orthotics to compensate for faulty foot mechanics. Activities may need to be begun on softer surfaces to acclimate to more rigorous ground reaction forces as higher activity levels are introduced.
Persistent effusion in the early postoperative period may result in quadriceps inhibition (reduced ability to voluntarily activate the quadriceps muscles). This can significantly retard progress with the rehabilitation program. Use of cold treatments, compression bandaging, limb elevation, and intermittent isometric contractions of the thigh and leg muscles may help resolve problems with effusion. If significant effusion persists more than 1 or 2 weeks after surgery, the therapist should notify the surgeon.
Quadriceps Inhibition or Persistent Knee Extensor Lag
Some patients may have difficulty with voluntary activation of the quadriceps muscles after surgery. This problem may be indicated by the inability to perform a full, sustained, isometric quadriceps contraction or the presence of a knee extensor lag on SLR. If patients exhibit this problem, they may not respond well to voluntary exercises alone. In addition, prolonged inability to actively achieve full knee extension may result in a knee flexion contracture that could, in turn, result in gait abnormalities and excessive loading of the knee during weight-bearing activities. Other treatment adjuncts to enhance quadriceps muscle activation such as neuromuscular electrical stimulation or EMG biofeedback may need to be incorporated into the program. If these treatment adjuncts are administered, the intensity of the treatment stimulus should be great enough to produce a full, sustained contraction of the quadriceps as evidenced by superior glide of the patella during the quadriceps contraction. Superior glide of the patella is important to prevent patellar entrapment in the intercondylar groove, which may sometimes be a causative factor in knee extensor lags. |
