Anterior Cruciate Ligament Injury 

Updated: Feb 26, 2021
Author: Matthew Gammons, MD; Chief Editor: Sherwin SW Ho, MD 

Overview

Practice Essentials

Anterior cruciate ligament (ACL) injuries are most often a result of low-velocity, noncontact, deceleration injuries and contact injuries with a rotational component. Contact sports also may produce injury to the ACL secondary to twisting, valgus stress, or hyperextension all directly related to contact or collision. The image below depicts a ruptured ACL.

MRI displaying a ruptured anterior cruciate ligame MRI displaying a ruptured anterior cruciate ligament.

Signs and symptoms

Symptoms of an acute ACL injury may include the following:

  • Feeling or hearing a “pop” sound in the knee

  • Pain and inability to continue activity

  • Swelling and instability of the knee

  • Development of a large hemarthrosis

See Clinical Presentation for more detail.

Diagnosis

Most ACL injuries may be diagnosed through a careful history emphasizing mechanism of injury coupled with a good physical examination.

Lachman test

The Lachman test is the most sensitive test for acute ACL rupture. It is performed with the knee in 30° of flexion, with the patient lying supine. The amount of displacement (in mm) and the quality of endpoint are assessed (eg, firm, marginal, soft). Asymmetry in side-to-side laxity or a soft endpoint is indicative of an ACL tear. Although difficult to measure, a side-to-side difference of greater than 3 mm is considered abnormal.

Pivot shift test

The pivot shift test is performed by extending an ACL-deficient knee, which results in a small amount of anterior translation of the tibia in relation to the femur. During flexion, the translation reduces, resulting in the "shifting or pivoting" of the tibia into its proper alignment on the femur. It is performed with the leg extended and the foot in internal rotation, and a valgus stress is applied to the tibia.

Anterior drawer test

The anterior drawer test is performed with the knee at 90° flexion, with the patient lying supine. There is an attempt to displace the tibia forward from the femur. If there is more than 6 mm of tibial displacement, an ACL tear is suggested. This test is not very sensitive and has been found to be positive in only 77% of patients with complete ACL rupture.

MRI

MRI has a sensitivity of 90-98% for ACL tears. MRI also may identify bone bruising, which is present in approximately 90% of ACL injuries.

An MRI allows the physician to confirm an ACL tear, but it should not be used as a substitute for a good history and physical examination.

See Workup for more detail.

Management

Nonoperative treatment

Nonoperative treatment may be considered in elderly patients or in less active athletes who may not be participating in any pivoting type of sports (eg, running, cycling). Arthroscopy may also be considered for persons who are poor candidates for reconstruction but have a mechanical block to range of motion.

Surgical intervention

Generally, the recommendation is that surgical intervention be delayed at least 3 weeks following injury to prevent the complication of arthrofibrosis. The methods of surgical repair may be categorized into 3 groups: primary repair, extra-articular repair, and intra-articular repair.

Primary repair is not recommended except for bony avulsions, which are mostly seen in adolescents. Because the ACL is intra-articular, the ligamentous ends are subjected to synovial fluid, which does not support ligamentous healing.

Extra-articular repair generally involves a tenodesis of the iliotibial tract. This may prevent a pivot shift but has not been shown to decrease anterior tibial translation.

Intra-articular reconstruction of the ACL has become the criterion standard for treating ACL tears.

See Treatment and Medication for more detail.

Background

Anterior cruciate ligament (ACL) injuries are most often a result of low-velocity, noncontact, deceleration injuries and contact injuries with a rotational component. Contact sports also may produce injury to the ACL secondary to twisting, valgus stress, or hyperextension, all directly related to contact or collision. The MRI image below shows a ruptured ACL.

MRI displaying a ruptured anterior cruciate ligame MRI displaying a ruptured anterior cruciate ligament.

When matched for activities, a greater prevalence for ACL injury is found in females compared with males. Approximately 50% of patients with ACL injuries also have meniscal tears. In acute ACL injuries, the lateral meniscus is more commonly torn; in chronic ACL tears, the medial meniscus is more commonly torn. The only study on the prevalence of ACL injuries in the general population has estimated the incidence as 1 case in 3,500 people, resulting in 95,000 new ACL ruptures per year.

The importance of the ACL has been emphasized in athletes who require stability in running, cutting, and kicking. The ACL-deficient knee has also been linked to an increased rate of degenerative changes and meniscal injuries. For these reasons, approximately 60,000-75,000 ACL reconstructions are performed annually in the United States.

For restoration of activity and stability, the expected long-term success rate of ACL reconstruction is between 75-95%. The current failure rate is 8%, which may be attributed to recurrent instability, graft failure, or arthrofibrosis.

Treatment options must be tailored to a patient's preoperative level of activity. The following activity levels are based on the International Knee Documentation Committee:

  • Level I includes jumping, pivoting, and hard cutting

  • Level II is heavy manual work or side-to-side sports

  • Level III encompasses light manual work and noncutting sports (eg, running and cycling)

  • Level IV is sedentary activity without sports

Nonsurgical treatment may be considered for patients who participate in level III or IV activities; all others should be considered as candidates for surgery. In addition, consider surgical consultation on any young athlete due to potential complications from recurrent instability.[1, 2, 3, 4, 5, 6]

Clinical studies

A randomized, prospective study by Wipfler et al comparing bone-patella-bone (BTB) autografts to hamstring tendon (HT) grafts at 9 years demonstrated significantly better International Knee Documentation Committee (IKDC) scores in the HT group, with no significant differences in laxity, tunnel widening, or any other parameters.[7]

Leys et al also found equivalent IKDC scores and better long-term outcomes (radiological evidence of osteoarthritis, level of activity, knee motion and single leg hop test) in HT versus BTB in a long-term cohort study following patients for 15 years postoperatively. The HT group had higher ipsilateral graft rupture rates (17% versus 8%), but lower contralateral ACL injury (12% versus 26%).[8]

One study compared the clinical outcomes of ACL reconstruction with hamstring tendon autograft versus irradiated allograft. The results found the rate of laxity with irradiated allograft was higher than that with autograft (32.3% vs 8.3%, respectively) in the 67 patients studied. Statistically significant differences were noted between the groups in the Lachman test (P = .00011), anterior drawer test (P = .00016), pivot-shift test (P = .008), and KT-2000 arthrometer assessment (P = .00021); the anterior and rotational stabilities decreased significantly in the irradiated allograft group. No significant differences were found between the 2 groups in functional and subjective evaluations, and activity level testing; however, patients in the irradiated allograft group had a shorter operative time and a longer duration of postoperative fever.[9]

Another study evaluated the outcome of anatomic double-bundle anterior cruciate ligament reconstruction with hamstring tendon autografts in both women and men. After a 2-year postoperative evaluation, the results noted that the assessment results for ligament laxity were approximately identical in both groups.[10]

The results from another study noted that 11 years after anterior cruciate ligament reconstruction, both hamstring and patellar tendon autografts provided good long-term outcomes and stability. However, a positive result on the pivot-shift (1+) test was significantly more frequent in the patellar tendon group, as was the rate of osteoarthritis.[11]

Geib et al compared intermediate-term outcomes of ACL reconstruction by bone-patellar tendon-bone (BPTB) with the outcomes associated with quadriceps tendon with a bone plug (BQT) and quadriceps tendon without a bone plug (QT). They found that QT and BQT produced results equivalent to those of BPTB autograft in arthroscopically assisted ACL reconstruction. When compared with BPTB autograft, the quadriceps tendon autograft showed significantly better results, with less anterior knee pain (4.56% vs 26.7%), less anterior numbness (1.5% vs 53.3%), a higher percentage of arthrometer measurements showing a side-to-side difference of 0 to 3 mm (88% vs 68%), and better extension (mean loss, 0.55º vs 2.77º).[12]

According to the results of a study by Marchant et al, computed tomography is the most reliable imaging modality for evaluation of ACL bone tunnels, as proven by superior intraobserver and interobserver testing results, when compared with results obtained with MRI and radiographs. According to the authors, radiographs and MRIs were not reliable even for identifying the presence of a bone tunnel. Intraobserver kappa scores for tibial cross-sectional area using CT, radiographs, and MRI were 0.66, 0.5, and 0.37, respectively. Interobserver kappa scores for tibial cross-sectional area using CT, radiographs, and MRI were 0.65, 0.39, and 0.32, respectively.[13]

According to a study of National Football League players by Brophy et al, a history of meniscectomy, but not ACL reconstruction, shortens the expected career of a professional football player, but a combination of ACL reconstruction and meniscectomy may be more detrimental to an athlete's durability than either surgery alone. In their study, 54 athletes with a history of meniscectomy, 29 with a history of ACL reconstruction, and 11 with a history of both were identified and matched with control subjects. Isolated meniscectomy reduced the length of career in both years (5.6 vs 7.0; P = .03) and games played (62 vs 85; P = .02). Isolated ACL surgery did not significantly reduce the length of career in years or games played. Athletes with a history of both surgeries had shorter careers in games started (7.9 vs 35.1; P < .01), games played (41 vs 63; P = .07), and years (4.0 vs 5.8; P = .08) than athletes with a history of either surgery alone.[14]

Lyman et al found that although ACL reconstruction appears to be a safe procedure, the risk of a subsequent operation on either knee is increased among younger patients and those treated by a lower-volume surgeon or at a lower-volume hospital. According to the authors, patients were at increased risk for readmission within 90 days after surgery if they were older than 40 years, sicker (eg, had a preexisting comorbidity), male, or operated on by a lower-volume surgeon. Predictors of subsequent knee surgery included being female, having concomitant knee surgery, and being operated on by a lower-volume surgeon. Predictors of a subsequent ACL reconstruction included age less than 40 years, concomitant meniscectomy or other knee surgery, and surgery in a lower-volume hospital.[4]

Functional Anatomy

The knee joint develops as a cleft between mesenchymal rudiments of the femur and the tibia. This occurs around the eighth week of fetal development. The cruciate ligaments appear as condensations of vascular synovial mesenchyme at the same time.

By 14 weeks' gestation, the ACL and posterior cruciate ligament have divided; both have a functional blood supply, which is mainly derived from the middle geniculate artery. The inferomedial and lateral genicular arteries also provide blood supply through the fat pad.

The ACL is composed of densely organized, fibrous collagenous connective tissue that attaches the femur to the tibia. The ACL is composed of 2 groups, the anteromedial and the posterolateral bands. During flexion, the anterior band is taut, while the posterior band is loose; during extension, the posterolateral band is tight, while the anterior band is loose.

The ACL attaches to bone through a transitional zone of fibrocartilage and mineralized cartilage. On the femur, the ACL is attached to a fossa on the posteromedial edge of the lateral femoral condyle. The tibial insertion is located in a fossa that is anterior and lateral to the anterior tibial spine. The tibial attachment is noted to be somewhat wider and stronger than the femoral attachment.

The ACL is intracapsular and extrasynovial. It courses anteriorly, medially, and distally as it runs from the femur to the tibia.

The ACL receives nerve fibers from the posterior branch of the posterior tibial nerve. The main function is believed to be proprioception, providing the afferent arc for postural changes during motion and ligament deformation.

Sport-Specific Biomechanics

The ACL is the primary (85%) restraint to limit anterior translation of the tibia. The greatest restraint is in full extension.

The ACL also serves as a secondary restraint to tibial rotation and varus/valgus angulation at full extension. Since the relationship between the tibia and femur provides little bony stability, the ligamentous structures must provide stability. When the ACL is injured, a combination of anterior translation and rotation occurs.

The average tensile strength for the ACL is 2160 N. This is slightly less than the strength of the posterior cruciate ligament and approximately half as strong as the medial collateral ligament (MCL).

Etiology

High-risk sports

Based on a study performed by Kaiser Permanente, football, baseball, soccer, skiing, and basketball account for up to 78% of sports-related injuries.

Hewson et al found a 100-fold increase in the incidence of ACL injury in college football players when compared to the general population.

Gender

Female athletes are more susceptible to ACL injuries. Studies have shown a 2-fold increase in collegiate soccer players and a 4-fold increase in basketball compared with their male counterparts.

Differences may be due to experience, differences in training, different strength-to-weight ratios, limb alignment, joint laxity, muscle recruitment patterns, and notch index, but further studies to document a definitive cause are ongoing. One study has determined that ACL laxity does not vary with the menstrual cycle, thus dismissing this possible etiology.

Femoral notch stenosis

Femoral notch stenosis is the ratio of the femoral notch width to the width of the femoral condyles. A notch width index of less than 0.2 is defined as notch stenosis. Individuals with notch stenosis have a higher risk of noncontact ACL injuries.

Footwear

Cleats, which have a predominant grip on the periphery, have a higher coefficient of friction on artificial turf and may result in a higher incidence of ACL injuries.

Epidemiology

United States data

An estimated 200,000 ACL-related injuries occur annually in the United States, with approximately 95,000 ACL ruptures. Approximately 100,000 ACL reconstructions are performed each year. The incidence of ACL injury is higher in people who participate in high-risk sports such as basketball, football, skiing, and soccer. When the frequency of participation is considered, a higher prevalence of injury is observed in females over males at a rate 2.4-9.7 times greater for females. A study by Gornitzky et al found that there is an approximately 1.6-fold greater rate of ACL tears per athletic exposure in high school female athletes than males.[15]

Prognosis

Patients treated with surgical reconstruction of the ACL have long-term success rates of 82-95%. Recurrent instability and graft failure is seen in approximately 8% of patients.

A study by Brophy et al found increased rates of chondral damage in patients who underwent partial meniscectomy compared to patients with a previous meniscal repair or no history of meniscal injury.[16]

Knee scores of those treated nonoperatively have fair/poor results up to 50% of the time. As many as 40% of patients treated nonoperatively have no episodes of giving way. The knee scores in this group may be too sensitive, not accurately representing the clinical situation.

Patients with ACL ruptures, even after successful reconstruction, are at risk for osteoarthrosis. The goal of surgery is to stabilize the knee, decrease the chance of future meniscal injury, and delay the arthritic process.

In a retrospective study of 135 young athletes (average age, 14 years) who underwent ACL reconstruction, Anderson et al found that the timing of surgery was related to the risk of secondary knee injuries. Compared with patients who had surgery within 6 weeks after an ACL injury, those who underwent surgery 6-12 weeks after injury had a 1.45 times higher risk of lateral meniscus injury, and those who underwent surgery more than 12 weeks after injury had a 2.82-fold increased risk. Risk for medial meniscal tears was 4.3 times higher when surgery was delayed at least 6 weeks. Other risk factors for secondary knee injuries were younger age, resumption of participation in sports before surgery, and earlier episodes of knee instability.[17]

Complications

The current failure rate for ACL reconstruction is approximately 8%. The 3 major categories of failure in an ACL reconstruction are (1) arthrofibrosis (due to inflammation of the synovium and fat pad), (2) pain that limits motion, and (3) recurrent instability, secondary to significant laxity in the reconstructed ligament. These factors may be related to the surgical procedure (eg, malpositioned tibial or femoral tunnels, misplaced hardware, inadequate notchplasty).

  • Anterior placement of a tibial tunnel may result in graft impingement. If a tunnel is placed too posteriorly on the femoral side, the posterior cortex of the femur may be violated.

  • A graft also may fail due to a lack of incorporation, secondary to rejection or stress shielding.

  • Trauma from re-injury or aggressive rehabilitation also may cause graft failure. The incidence of graft re-rupture is approximately 2.5%.

Other complications include patella fractures and patella-tendon ruptures. Reflex sympathetic dystrophy, postoperative infection, and neurovascular complications are rare (each accounting for less than 1% of complications). The rate of postoperative deep venous thrombosis is approximately 0.12%.

 

Presentation

History

Most ACL injuries may be diagnosed through a careful history emphasizing mechanism of injury coupled with a good physical examination. Remember that a previous ligamentous injury may be the cause of instability. When discussing the history, be sure to document mechanism of injury for this episode and any previous episodes.

Noncontact injury

An audible pop often accompanies this injury, which often occurs while changing direction, cutting, or landing from a jump (usually a hyperextension/pivot combination). Within a few hours, a large hemarthrosis develops.

Patients usually are unable to return to play, secondary to pain, swelling, and instability or giving way of the knee.

Contact and high-energy traumatic injuries

These injuries often are associated with other ligamentous and meniscal injuries. The classic "terrible triad" (ACL, MCL, and medial meniscus tears) involves a valgus stress to the knee with resultant acute injury to the ACL and MCL; however, the medial meniscus tear is now thought to occur later, as a result of chronic ACL deficiency.

Physical Examination

An organized, systematic physical examination is imperative when examining any joint. The Dutch Orthopaedic Association clinical guidelines for the treatment of ACL injury recommend the Lachman test, pivot shift test, and anterior drawer test for diagnosis.[18]  Note that a study found the sensitivity of these tests is lower in obese patients (body mass index of ≥30) than in those who are not obese.[19]

Immediately after the acute injury, the physical examination may be very limited due to apprehension and guarding by the patient.

The examiner should begin with inspection, looking for any gross effusion or bony abnormality. An immediate effusion indicates significant intra-articular trauma. According to Noyes et al, in the absence of bony trauma, an immediate effusion is believed to have a 72% correlation with an ACL injury of some degree.

Assess the patient's range of motion (ROM), especially looking for lack of complete extension, secondary to a possible bucket-handle meniscus tear or associated loose fragment.

Palpation of bony structures may suggest an associated tibial plateau fracture.

Palpation of the joint lines to evaluate a possible associated meniscus tear. Palpation over the collateral ligaments to suggest any possible injury (sprain) of these structures. Up to 50% of ACL ruptures have associated meniscal injuries; acute injuries are likely to have associated injuries of the MCL and meniscus.

Ligamentous laxity may be difficult to detect in the acute situation. The Lachman test, as shown in the image below, is the most sensitive test for acute ACL rupture. Since the Lachman test must be performed when the patient is relaxed, it is often better to conduct this test prior to manipulating the painful knee.

Proper technique for the Lachman test. Proper technique for the Lachman test.

The knee is placed in a position of 20-30° of flexion. The femur is stabilized with a nondominant hand, and an anteriorly directed force is applied to the proximal calf.

The amount of displacement (in mm) and the quality of endpoint are assessed (eg, firm, marginal, soft). Asymmetry in side-to-side laxity or a soft endpoint is indicative of an ACL tear. Although difficult to measure, a side-to-side difference of greater than 3 mm is considered abnormal.

Other ligamentous tests are less reliable especially for primary care providers who may not have as much experience in using these maneuvers. The pivot shift test, as shown in the image below, is performed by extending an ACL-deficient knee, which results in a small amount of anterior translation of the tibia in relation to the femur. During flexion, the translation reduces, resulting in the "shifting or pivoting" of the tibia into its proper alignment on the femur.

The pivot shift test. The pivot shift test.

The pivot shift test is performed with the leg extended, the foot in internal rotation, and a valgus stress is applied to the tibia. Flexion causes a reduction of the anteriorly subluxed tibia at approximately 20-30°.

The anterior drawer test, as shown in the image below, may be influenced by hamstring spasm in the acutely injured knee; thus, this test is considered the least reliable.

Anterior drawer test: Note the anterior excursion Anterior drawer test: Note the anterior excursion of the tibia in relationship to the femur.

This test is performed with the patient supine and the knee flexed to 90°. The examiner can sit on the patient's foot and grasp around the patient's calf with both hands. An anterior force is applied, and tibial excursion is compared to the unaffected knee.

 

DDx

 

Workup

Laboratory Studies

Arthrocentesis

Blood with fat globules are indicative of an osteochondral or tibial fracture.

Tapping of the knee is rarely performed with the advent of other less invasive and more specific diagnostic tests (magnetic resonance imaging [MRI]).

Imaging Studies

Plain radiographs

Radiographic findings are usually negative. Anteroposterior, lateral, merchant, sunrise, and notch views may be used by the physician to diagnose certain radiographic findings that are associated with ACL ruptures. Oblique radiographs may be helpful to exclude tibial plateau fractures.

The Segond fracture (lateral capsular avulsion fracture) may be visualized on an anteroposterior view. This is an avulsion fracture of the lateral tibial plateau, located near the joint line and posteriorly to the Gerdy tubercle. The Segond fracture represents a disruption of the meniscotibial portion of the lateral capsule. Segond fracture is direct evidence of a lateral capsule injury and indirect evidence of an ACL injury.

The lateral notch fracture (lateral view) is located in the lateral femoral condyle. This type of fracture is more commonly seen in chronic ACL-deficient knees, resulting from anterior subluxation of the lateral tibial plateau. The physician must differentiate lateral notch fractures from osteochondral defects or fractures.

Arthrograms

These studies have generally been replaced by MRI. Arthrograms are mostly of historical interest, having occasionally been used by physicians to diagnose ACL ruptures; they must be performed by a radiologist who is highly skilled in double-contrast arthrography.

MRI

MRI has a sensitivity of 90-98% for ACL tears. MRI also may identify bone bruising, which is present in approximately 90% of ACL injuries. An MRI scan allows the physician to confirm an ACL tear, but it should not be used as a substitute for a good history and physical examination. According to the Dutch Orthopaedic Association clinical guidelines for the treatment of ACL injury, MRI has no additional value when physical examination has shown anterior-posterior or rotational instability of the knee. However, MRI is reliable for establishing other intraarticular lesions.[18]

Other Tests

Instrumented ligament testing

KT-1000 compares the difference in tibial excursion between the injured and the unaffected knee of a patient.

An excursion greater than 3 mm as measured by the KT-1000 is classified as pathologic.

 

Treatment

Acute Phase

Rehabilitation program

Physical therapy

Before any treatment, encourage strengthening of the quadriceps and hamstrings, as well as range of motion (ROM) exercises. Performance of ROM helps reduce the amount of effusion and helps the patient regain motion and strength.

Surgical intervention

When deciding whether to perform reconstructive surgery, the physician should consider the following factors:

  • Preinjury activity level

  • Desire to return to high-demand sports (eg, basketball, football, soccer)

  • Associated injuries

  • Abnormal laxity

  • Patient's expectations

Generally, the recommendation is that surgical intervention be delayed at least 3 weeks following injury to prevent the complication of arthrofibrosis. However, the results of one study noted that increased time to surgery (6-12 mo and >12 mo) is strongly associated with a higher risk of medial meniscus injury and decreased repair rate. While females experienced a lower risk of cartilage injury, increasing age and increasing time to surgery (>12 mo) in male patients realized a greater risk.[20]

The methods of surgical repair may be categorized into 3 groups, primary repair, extra-articular repair, and intra-articular repair.

  • Primary repair is not recommended except for bony avulsions, which are mostly seen in adolescents. Because the ACL is intra-articular, the ligamentous ends are subjected to synovial fluid, which does not support ligamentous healing.

  • Extra-articular repair generally involves a tenodesis of the iliotibial tract. This may prevent a pivot shift but has not been shown to decrease anterior tibial translation.

  • Intra-articular reconstruction of the ACL has become the criterion standard for treating ACL tears.

    • Bone-patella-bone (BTB) autografts are currently popular because they yield a significantly higher percentage of stable knees with a higher rate of return to preinjury sports. The major pitfall of these grafts is their association with postoperative anterior knee pain (10-40%).

    • Hamstring tendon (HT) grafts are associated with a faster recovery and less anterior knee pain. Critics believe that these are more susceptible to graft elongation; however, a recent randomized, prospective study by Wipfler et al comparing BTB autografts to HT grafts at 9 years demonstrated significantly better International Knee Documentation Committee (IKDC) scores in the HT group, with no significant differences in laxity, tunnel widening, or any other parameters.[7]

    • Recent literature has supported a greater tensile strength with the use of braided quadruple hamstring grafts. However, this finding has not been confirmed in vivo, and the graft may be limited by the type of fixation.

    • Allografts have also been very popular because of their efficiency, their ability to provide bony fixation, and the lack of associated patella morbidity. However, they are associated with a risk of viral transmission. Allografts are best used in revisions. These have also fallen out of favor by some because several deaths linked to clostridial infections from inadequate sterilization techniques have been reported, which led to increased research into sterilization techniques to ensure safety. In addition, concerns exist regarding what effects the immunologic response and delayed revascularization and remodeling may have on clinical outcomes. Although allografts are generally accepted as having less associated morbidity, no proof of this is present in the literature.

    • Synthetic grafts and ligament augmentation devices have also been used. Synthetic grafts are no longer acceptable, because of their high rate of complications, including failure and aseptic effusions.

    • Intra-articular reconstruction may be performed through a 2-incision technique or a single-incision endoscopic technique; the latter is currently more popular. This procedure requires graft stabilization with some type of fixation hardware for all of the graft options. The stabilization may be performed with metal interference screws, bioabsorbable screws, endobuttons, and cross pins. Each device has its own benefits.

    • Double-tunnel ACL reconstructions attempt to reproduce stability in internal rotation and valgus torque applied to the knee. Investigations into the benefits of such surgical treatment versus the increased level of difficulty and operative time are currently ongoing. Studies at this time have been limited to animal models.

    • The results of a 2-year randomized trial noted that the double-bundle technique resulted in fewer graft failures and significantly lower revision rates than the single-bundle technique in anterior cruciate ligament reconstruction.[21]

    • After a 3-year follow up, the data from one study showed that patients with combined lesions of the ACL and MCL who had undergone an arthroscopic double-bundle ACL reconstruction showed a significantly greater mean medial joint opening (1.7 mm) compared with uninjured knees (0.9 mm). However, no significant difference was noted between the anteroposterior laxity and other clinical parameters. Because the data showed that residual valgus laxity did not affect anteroposterior laxity significantly, these results suggest that no additional surgical procedure is necessary for the medial collateral ligament in combined lesions.[22]

Other treatment

Nonoperative treatment may be considered in elderly patients or in less active athletes who may not be participating in any pivoting type of sports (eg, running, cycling). The goal is to obtain a full ROM and strength compared with the uninjured knee. This modality of treatment requires modification of activity levels and avoidance of physically demanding occupations. Arthroscopy may also be considered for persons who are poor candidates for reconstruction but have a mechanical block to ROM. The goal of this procedure is to debride the remaining stump to increase motion. Patients with significant arthritis are also thought to be poor candidates unless they are experiencing recurrent instability.

Recovery Phase

Rehabilitation program

Physical therapy

Postoperative treatment is discussed.

  • Closed-chain exercises are used to emphasize early and long-term maintenance of full extension.

  • Therapy protocols may be divided into the following 4 categories per Shelbourne and Nitz[23] :

    • Phase I: This is the preoperative period when the goal is to maintain full ROM.

    • Phase II (0-2 wk): The goal is to achieve full extension, maintain quadriceps control, minimize swelling, and achieve flexion to 90o.

    • Phase III (3-5 wk): Maintain full extension and increase flexion up to full ROM. Stair-climbers and bicycles may be used.

    • Phase IV (6 wk): Increase strength and agility, progressive return to sports. Return to all sports without activity may take 6-9 months and should be closely monitored by the surgeon and physical therapist.

Other treatment (injection, manipulation, etc)

The use of knee braces remains a highly controversial topic; braces are well accepted by patients, but most biomechanical studies do not support their use. Studies have shown that functional bracing can limit anterior translation of the tibia at low loads. Furthermore, most braces have been found to decrease the reaction time of the hamstring muscles.

Maintenance Phase

Rehabilitation program

Physical therapy

Open-chain exercises are initiated. The patient's timeframe for returning to sports depends on his/her strength, ROM, and the type of fixation that was performed.

 

Guidelines

Guidelines Summary

AAOS practice guideline for ACL tears

The American Academy of Orthopaedic Surgeons (AAOS) has issued evidence-based practice guideline for the management of ACL tears. Recommendations include the following[24, 25] :

  • To protect the knee joint, patients who are surgical candidates should undergo reconstructive surgery within 5 months following an ACL injury; however, the evidence for this recommendation was considered to be only moderate

  • A relevant history should be obtained and a musculoskeletal exam of the lower extremities performed

  • Magnetic resonance imaging (MRI) should be performed to confirm the ACL diagnosis and reveal any associated joint and cartilage problems

  • Either autograft or appropriately processed allograft tissue can be used in ACL reconstruction, since measured outcomes for both types of graft have been similar; however, the guideline cautions that such results may not apply in all cases

  • Patellar or hamstring tendons should be used in intra-articular ACL reconstruction employing autograft tissue

  • A single- or double-bundle technique should be used in intra-articular ACL reconstruction; both techniques have similar measured outcomes

American Academy of Pediatrics guidelines

In 2014, the American Academy of Pediatrics released clinical guidelines on the diagnosis, treatment, and prevention of ACL injuries in children and adolescents.[26, 27] Recommendations include the following:

  • The best physical examination test for detecting an ACL tear is the Lachman test

  • MRI may be necessary in young patients in whom physical examination is not possible because of pain, swelling, and/or lack of cooperation

  • ACL tears in pediatric patients are not a surgical emergency, and patients should explore their options

  • In young patients who are skeletally immature, measurement of skeletal age with an anteroposterior radiograph of the left hand and wrist and Tanner stage may help guide treatment

  • Treatment of ACL injuries often involves surgery and/or months of rehabilitation

  • Pediatric patients with ACL tears are at increased risk for early-onset osteoarthritis in the affected knee

  • Musculoskeletal changes that affect dynamic joint stability may be the most important factor underlying the higher rate of noncontact ACL injuries in adolescent female athletes; neuromuscular training initiated in early to middle adolescence may reduce their risk

 

Medication

Medication Summary

Medication for ACL injuries mainly consists of analgesics. Preoperative drugs may include cyclooxygenase-2 (COX-2) inhibitors and opioid analgesic agents. Postoperatively, the patient may obtain pain relief through nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid analgesics. NSAIDS have been shown to decrease bone formation in spine fusions and rotator cuff surgery. Although this has not been seen clinically in ACL reconstructions with bone-patella tendon-bone grafts, it is plausible to think that this may be the case. Therefore, long-term postoperative use may not be beneficial.

Nonsteroidal anti-inflammatory drugs

Class Summary

Have analgesic and anti-inflammatory activities. Their mechanism of action is not known, but may inhibit cyclooxygenase activity and prostaglandin synthesis. Other mechanisms may exist as well, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation and various cell membrane functions.

Ketorolac (Toradol)

Inhibits prostaglandin synthesis by decreasing the activity of the enzyme, cyclo-oxygenase, which results in decreased formation of prostaglandin precursors. Used in postoperative pain control.

Ketorolac intranasal (Sprix)

NSAID; inhibits cyclooxygenase (COX), an early component of the arachidonic acid cascade, resulting in reduced synthesis of prostaglandins, thromboxanes, and prostacyclin. Elicits anti-inflammatory, analgesic, and antipyretic effects. Indicated for short-term (up to 5 d) management of moderate to moderately severe pain. Bioavailability of 31.5-mg intranasal dose (2 sprays) is approximately 60% of 30-mg IM dose. Intranasal spray delivers 15.75 mg per 100-µL spray; each 1.7-g bottle contains 8 sprays.

Cyclooxygenase-2 inhibitors

Class Summary

Although increased cost can be a negative factor, the incidence of costly and potentially fatal GI bleeds is clearly less with COX-2 inhibitors than with traditional NSAIDs. Ongoing analysis of cost avoidance of GI bleeds will further define the populations that will find COX-2 inhibitors the most beneficial.

Celecoxib (Celebrex)

Inhibits primarily COX-2. COX-2 is considered an inducible isoenzyme, induced during pain and inflammatory stimuli. Inhibition of COX-1 may contribute to NSAID GI toxicity. At therapeutic concentrations, COX-1 isoenzyme is not inhibited thus GI toxicity may be decreased. Seek lowest dose of celecoxib for each patient. Used for postoperative pain control.

 

Follow-up

Return to Play

Once quadriceps strength reaches 65% of the opposite leg, sports-specific activities may be performed; this usually occurs within 5-8 weeks postsurgery. This may be tested using a Cybex machine. The athlete may return to activity when the quadriceps strength has reached 80%, which is usually after at least 3-4 months of sports-specific therapy.

According to a study by Grindem et al, returning to level I sports after ACL reconstruction leads to a more than 4-fold increase in reinjury rates over 2 years. The study also found that return to sport 9 months or later after surgery and more symmetrical quadriceps strength prior to return substantially reduce the reinjury rate.[28]

A study by Kyritsis et al found that athletes who did not meet the discharge criteria before returning to professional sport had a four times greater risk of sustaining an ACL graft rupture compared with those who met all six return to sport criteria. The study also found that hamstring to quadriceps strength ratio deficits were associated with an increased risk of an ACL graft rupture.[29]