Rehabilitation for Anterior Cruciate Ligament Injury Treatment & Management

Updated: Jan 26, 2023
  • Author: Tarek O Souryal, MD; Chief Editor: Stephen Kishner, MD, MHA  more...
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Rehabilitation Program

Physical Therapy

The primary goals in the treatment of anterior cruciate ligament (ACL) rupture are restoration of function in the short term and the prevention of long-term pathologic changes in the knee. Nonoperative treatment is a reasonable approach in patients who are not athletically active.

Research has demonstrated that the natural history of untreated complete injuries of the ACL consists of the progression of symptomatic instability to recurrent injuries. These injuries damage the menisci and the articular cartilage, eventually leading to osteoarthritis and osteoarthrosis. [17]

The key to successful treatment of an ACL tear is proper and early rehabilitation. Preoperative and postoperative rehabilitation programs are similar initially. Swelling control and restoration of motion and strength are the goals of each.

A study by Łyp et al indicated that following rupture of the ACL, the degree of rehabilitation success is inversely related to the length of time between reconstruction and the start of rehabilitation but is not associated with the amount of time passing between ACL rupture and reconstruction. [18]

The postoperative rehabilitation program begins as soon as the patient awakens from anesthesia, especially because patients are discharged earlier now than they were in previous years. Quadriceps co-contractions make up the first exercise that patients should be taught for the maintenance of terminal extension.

Passive motion is emphasized, with active flexion and assisted extension in the sitting or prone position to ensure good leg control (ie, ability to flex the hip and lift the leg against gravity without assistance). A continuous passive motion machine can be used to establish 0-30° of motion immediately postoperatively and to progress to 60° of knee flexion by the morning following the operation. The patient then begins gait training with crutches (weight bearing as tolerated), with the knee in an immobilizer. The patient usually can be discharged on the first postoperative day and should be encouraged to avoid crowds, keep the leg elevated when not ambulating, use the crutches at all times for protection, and continue frequent icing.

A number of different programs are used by different physical therapists. The therapy program chosen depends on the activity level of the patient and the type of surgery performed, coexistent injuries (meniscal or other ligamentous injury), the surgeon, the insurance policy, and time constraints.

Goal-oriented rehabilitation for patellar tendon grafts

The following rehabilitation program is an accelerated program for patellar tendon grafts. Note that the other grafts rehabilitate slightly differently. This rehabilitation program is classified as a goal-oriented approach. The dates listed are not meant to be followed strictly and can be varied by a day or 2, depending on the physician or the patient's schedule.

On day 3 following surgery, have the patient return to the surgeon for evaluation. Begin therapy on an outpatient basis, concentrating on gait training and other ambulation-oriented activities. The goal is to maintain terminal knee extension and progression toward 90° of flexion. The therapist emphasizes a normal heel-to-toe gait pattern, and the patient may weight bear as tolerated on the involved leg. Continue passive flexion ROM exercises. Have the patient increase quadriceps activity, introducing the partial squat with progression from bilateral to unilateral, placing increased body weight on the extremity involved at no more than 45° of flexion. Continue these exercises for 1 week. Continue the knee immobilizer when ambulating and continue regular icing of the knee.

On day 10 following surgery, have the patient return to the surgeon for evaluation. Advance therapy to include wall slide-squats and a stationary bike as tolerated. Place emphasis on terminal extension, progressive flexion, and full weight-bearing ambulation with normal heel-to-toe mechanics. In a controlled environment (no pets, children, or distractions), have the patient begin practicing crutch ambulation while out of the knee immobilizer. The patient should achieve full terminal knee extension and approximately 90-100° of knee flexion.

Three to 4 weeks after the surgery, the aggressive patient is ambulating with normal gait mechanics. At this point, the knee immobilizer can be removed. Advance the patient's activity to include loaded squats, swimming, eccentric quadriceps strengthening, bridging with a physioball, and a stair stepper. During this time, if the therapist is not observant, the patient can develop tendonitis of the quadriceps tendon or other repetitive use injuries of the lower extremity. Application of ice after each therapy session is very important.

Six weeks after surgery, release the patient to light jogging or bicycling. If the patient is older and has concomitant degenerative joint disease, encourage bicycling. The graft is still very weak at this stage, so advise the patient that it is important not to fall. The patient should jog only on a track or other flat protected surface. At this point, active ROM should be approaching 0-125° with minimal or no joint effusion. Work on balance and proprioception with activity drills.

At 3 months, recommend that the patient begin a gradual return to normal activities. At this point, most people do not require bracing, but occasionally, some athletes request a brace to increase their own comfort level when competing.

Open kinetic chain (OKC) and closed kinetic chain (CKC) exercises

Significant discussion surrounds the difference between OKC and CKC exercises during ACL rehabilitation. The difference concerns the assumption that CKC exercises are safer than OKC exercises because they place less strain on the ACL graft, producing less patellofemoral pain. The second assumption is that CKC exercises are more functional and are equally effective in improving quadriceps muscle force production.

A study by Beynnon and colleagues showed no difference in ACL strain characteristics between OKC and CKC exercises. [19, 20] A report by Fleming and coauthors argues that, with improved anatomical placement of the ACL graft, the graft may respond more like the intact ACL during OKC and CKC exercises. Therefore, these 2 articles argue that both types of exercise can be performed safely.

With regard to safety, OKC and CKC exercises can be applied in a manner that minimizes the risk of excessive graft strain and patellofemoral compression. Using different knee joint motion excursions for each type of exercise is the key to risk reduction. When OKC knee extensions are performed, limit knee joint motion to more flexed positions. During CKC lower extremity exercises, limit knee joint motions to more extended positions.

Nonoperative treatment

Patients may for a variety of reasons—if, for example, they are not highly active or athletic or are minimally symptomatic—opt for nonoperative treatment. In these cases, after initial control of pain and effusion, start hamstring and quadriceps activation/disinhibition and protected weight bearing in a hinged brace. As swelling and pain slowly resolve, ROM should return to normal, or nearly normal, parameters. Start exercises that take place in an anterior/posterior plane (eg, stationary cycling). Exercises need to be nonballistic.


Surgical Intervention

Several options exist for the patient who elects to have surgery. For complete rupture, no local healing response is detectable at the injury site, and a graft must be used to replace the ACL. [1] Today, 4 options are used. The first 3 types are autografts using the central one third of the patellar tendon (considered a bone-tendon-bone graft), the quadruple semitendinosus/gracilis tendon, or the quadriceps tendon. [2, 3] The fourth type of graft is a cadaveric allograft.


The patellar tendon with its bony ends has been a popular ACL replacement because of its high ultimate tensile load (~2300 N), its stiffness (~620 N/mm), and the possibility for rigid fixation with its attached bone graft.

By comparison, the dimensions of a round, 10-mm quadruple semitendinosus/gracilis tendon graft (hamstring graft) are more comparable to those of the intact ACL, and its ultimate tensile load has been reported to be as high as 4108 N. The quadruple tendon graft also may provide a multiple bundle replacement graft that better approximates the function of the 2-bundle ACL. Disadvantages of this soft-tissue graft include concern over tendon healing within the osseous tunnels and a lack of rigid bony fixation. A 1998 study from Japan suggests that aggressive early rehabilitation after an ACL reconstruction using the hamstring graft has more risk for residual laxity than does the patellar tendon graft. [21]

The quadriceps tendon graft has been shown to have an ultimate tensile load of as high as 2352 N. This graft has become an alternative replacement graft, especially for revision ACL surgeries and for patients with multiple ligament injuries in the knee.

In patients who are very skeletally immature, an iliotibial band autograft may be used, with the graft “attached over the top of the lateral femoral condyle and over the front of the tibia.” [22]

Cadaver studies have shown that the strength of fixation between the patellar tendon graft and the hamstring graft is equal to approximately 450 N, but the patellar graft can achieve fixation strength of as high as 1000 N. Grafts fixed to bone close to the articular surface (ie, patellar tendon grafts) undergo less strain and are stiffer than are those grafts fixed outside of drill holes (ie, hamstring grafts).


Allograft tissues are harvested from human donors and typically include either the patellar tendon or the Achilles tendon.

Allografts are used for multiple ligament reconstructions and revisions of ligament reconstructions, as well as for the treatment of patients who are not high-performance athletes. However, the reduction of tensile strength that occurs with sterilization is a concern, as is the risk of inflammatory reactions.

Choice of graft type

In a prospective comparative 9-year follow-up study by Wipfler et al, the authors review the innovative technique of implant-free press-fit ACL reconstruction with bone–patellar tendon or quadrupled hamstring tendon grafts. This technique saves the cartilage and meniscal status of the knee, leaving little long-term differences between the operated and nonoperated knee. No significant differences, between the two groups, were found with range of motion, pivot-shift test, or quadriceps strength. Anterior knee pain was considerably less when kneeling and knee walking for those who underwent quadrupled hamstring tendon grafts, but hamstring strength was decreased. [23]

Ultimately, the decision as to which graft is best is still a matter of contention. The agreement is that the patellar and hamstring grafts are superior to the quadriceps graft and the allograft; however, the decision as to which is the better of the patellar and hamstring grafts depends on which surgeon is operating.

With regard to osteoarthritis, hamstring grafts have shown a lower rate of radiological osteoarthritis than patellar grafts at 15 years postsurgery. [24] In spite of the type of graft, some patients will develop osteoarthritis in the reconstructed knee, especially patients with concomitant or subsequent meniscectomy.


A prospective study by Müller et al indicated that results from the single-hop test for distance and the Anterior Cruciate Ligament-Return to Sport After Injury Scale (ACL-RSI) are significant factors in predicting whether an athlete will return to a preinjury level of sport after ACL reconstruction. [25]

In the study, 40 patients who underwent semitendinosus tendon autograft for an ACL rupture were assessed 6 months postoperatively with a variety of tools—including four single-leg hop tests, the ACL-RSI, the 2000 International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, the Tampa Scale of Kinesiphobia-11 (TSK-11), and evaluation of knee extensor and flexor strength—to determine which of these could most effectively predict whether a patient was likely to return to his/her preinjury level of sport. Patients were then interviewed at 7 months postoperatively to identify which of them could be classified as “return to sport” (RS) or “non-return to sport” (nRS). [25]

The investigators found that the single-hop-for-distance limb symmetry index value, with a cutoff point of 75.4%, and the ACL-RSI, with a cutoff point of 51.3 points, had sensitivities of 0.74 and 0.97, respectively, and specificities of 0.88 and 0.63, respectively, for predicting which patients would fall into the RS or nRS group. [25]

A study by Villa et al found that the following factors had a positive influence on recovery in patients following ACL reconstruction: age younger than 20 years, a higher preinjury Tegner activity scale score, professional-level sports practice, an absence of concurrent capsular lesions and of postoperative knee bracing, a higher percentage of on-field rehabilitation sessions during patients’ customized rehabilitation protocol, and a deficit in knee flexor and extensor strength of less than 20% at the first isokinetic knee test. [26]

A study by Paterno et al indicated that when a 90% threshold is used, current criteria for RS fail to determine whether a high risk for a second ACL injury exists in active, skeletally mature adolescent and young adult athletes following ACL reconstruction. The criterion level for passing any of the six RS tests in the study was 90% limb symmetry. However, the investigators found that at 2 years post RS, in athletes who passed all six tests, the rate of second ACL injury (28.6%) did not significantly differ from that (19.7%) of athletes who failed at least one of the tests. The evaluation measures included the International Knee Documentation Committee Subjective Knee Evaluation Form score, the quadriceps limb symmetry index, the single-leg hop for distance, the triple hop for distance, the crossover hop for distance, and the 6-meter timed hop. [27]



In anterior cruciate ligament injury cases, presurgical consultations with other services generally are needed only in connection with surgical clearance. After surgery, it is important to consult with a specialist in physical medicine and rehabilitation (PMR) for initiation of a program to facilitate the patient's rehabilitation.


Other Treatment

Some patients, especially those who are minimally involved in sports, elect not to have surgery and instead choose bracing. Several custom and off-the-shelf, anterior cruciate ligament–specific braces are available. For patients who are involved in vigorous sports, the use of braces without surgical stabilization is not recommended.