I. Anterior Cruciate Ligament Injuries
A. Overview and epidemiology
1. The anterior cruciate ligament (ACL) is most commonly injured during sports-related activity, with a minority of ACL injuries occurring in high-energy trauma or activities of daily living.
2. Approximately 70% of patients hear or feel a pop at the time of injury.
3. Almost all patients notice swelling of the knee within 24 to 48 hours of the injury.
4. Injuries may be classified as contact or noncontact injuries. Noncontact injuries usually occur with cutting or pivoting.
5. Female athletes have a two- to four-fold higher risk of ACL injury than males when level of competition, age, and time exposed are taken into consideration.
a. The reason for the higher rate of injuries among females is not clearly understood.
b. Potential contributing factors include biomechanics, alignment, muscle strength, hormonal factors, and training.
B. Pathoanatomy
1. The overwhelming majority of ACL injuries are complete disruptions.
2. In the skeletally mature patient, the femoral insertion or midsubstance is usually the site of disruption.
3. In the skeletally immature patient, the tibial attachment may be avulsed with or without a piece of bone.
*Jon K. Sekiya, MD, or the department with which he is affiliated has received research or institutional support, miscellaneous non-income support, commercially derived honoraria, or other nonresearch-related funding and royalties from Arthrex and is a consultant for or an employee of Arthrex.
C. Evaluation
1. History
a. An appropriate and detailed patient history can raise suspicion for an ACL injury.
b. The patient who sustains a knee injury during sports activity that is followed by sudden knee swelling should be carefully evaluated for a possible ACL injury.
i. ACL injuries are also extremely common during skiing.
ii. Conversely, ACL injuries are less common among snowboarders.
c. In the setting of chronic ACL injury, the patient may have recurrent episodes of knee injury, mechanical symptoms from a secondary meniscal tear, or frank instability.
2. Physical examination
a. In the setting of acute ACL injury, physical examination can be difficult or limited secondary to pain.
b. Effusion is related to hemarthrosis, secondary to bleeding from the vascular, torn ligament.
c. The knee should be palpated carefully, with attention focused on the joint lines and the femoral origin of the medial collateral ligament (MCL) in particular.
d. Patient apprehension on movement of the patella should be noted, since acute patellar dislocations often present with a history that is very similar to ACL injury, and the two injuries can be confused in the acute setting.
e. The quadriceps and patellar tendons also should be examined in the acute setting, as tendon ruptures may be confused with ACL injuries.
f. The Lachman test is the most useful in diagnosing ACL injuries in the acute setting. In the Lachman test, the distal femur is held securely in one hand while the examiner translates the tibia anteriorly with the other hand. A sense of increased movement and lack of a solid end point are indicative of ACL injury.
g. The collateral ligaments must also be assessed for stability with varus and valgus stress and rotation.
h. The posterior cruciate ligament (PCL) must also be examined. Ideally, this is done with the knee at 90° of flexion; however, this maneuver is often difficult in the acute setting because the patient is in pain.
i. Neurovascular injury must be ruled out by assessing motor and sensory function as well as pedal pulses.
i. In multiligament injuries with higher-energy trauma, vascular injuries can occur.
ii. With posterolateral corner injuries and a varus stress, peroneal injuries can also be found.
j. The pivot-shift test is pathognomonic for ACL injury (best in the chronic setting).
i. This test begins with the knee in full extension, and the knee is then flexed while applying a valgus moment.
ii. As the iliotibial band passes posterior to the axis of knee rotation at approximately 15° of knee flexion, the tibia (which is subluxated anteriorly on the femur) reduces with a visible shift at the lateral joint line.
iii. This should always be compared with the contralateral side, where a physiologic pivot shift or pivot glide may occasionally be present.
k. The patient who does not have a clearly positive examination for an acute ACL injury may have a partial ACL injury, despite a positive MRI.
i. Partial ACL injuries require strict physical examination and visualization criteria.
ii. Partial injuries may or may not withstand future trauma, allowing the knee to give way.
3. Imaging
a. Radiographs are useful in the acute setting to rule out fracture.
b. In the skeletally immature patient, radiographs should be evaluated for open physes, particularly because this can impact surgical options.
c. MRI is not required for the diagnosis of ACL injury, but it is useful for assessing for meniscal pathology, subchondral fracture ("bone bruise"), and other ligamentous injury.
[
Figure 1. Lateral T2-weighted MRI demonstrating a typical "bone bruise" of the anterior lateral femoral condyle and posterior lateral tibial plateau. This type of injury is believed to result from an anterior translational event of the tibia in reference to the femur secondary to an ACL injury.]
i. A characteristic edema pattern on MRI, particularly in the acute setting, relates to transchondral fractures in the posterolateral tibial plateau and the more anterolateral femoral condyle, and it is indicative of a translational event that is likely secondary to an ACL injury (Figure 1).
ii. In sagittal and coronal MRI scans, ACL injuries appear as disruptions in the normal black ACL fiber.
D. Treatment
1. Nonsurgical
a. Individualized treatment is appropriate for patients with partial injuries to the ACL, including those with low-energy skiing injuries, who may have a good outcome with nonsurgical treatment.
b. Nonsurgical treatment involves rehabilitation to strengthen hamstrings and quadriceps, as well as proprioceptive training.
c. Activity modification is also an important part of nonsurgical management, as patients who avoid cutting and pivoting sports are at lower risk for knee instability.
d. ACL sports braces are available as well. However, they have not been shown to prevent abnormal anterior tibial translation. Functional braces and simple knee sleeves improve proprioception, which may give patients a sense of improved knee function and stability.
2. Surgical
a. Indications—In the acute setting, the decision to reconstruct the ACL is generally related to the patient's activity level.
i. Patients who are older or less physically active may elect to modify their activities and proceed with nonsurgical treatment. If non-surgical treatment fails or knee instability persists, surgery can be performed.
ii. Athletes with ACL injuries rarely return to cutting and pivoting sports, such as basketball, football, soccer, squash, and handball, without first undergoing surgery. For individuals who wish to return to such sports, surgery is generally recommended to avoid instability and secondary meniscal and/or articular cartilage damage.
iii. The decision about whether ACL surgery is needed for an individual to return to sports activity is not always obvious. Many recreational skiers who do not participate in cutting and pivoting sports can often function well without surgery.
iv. Individuals who work in occupations that may involve physical combat, such as police officers, or risk, such as firefighters, should have ACL reconstruction before returning to work.
v. Most patients can function well and perform activities of daily living (ADLs) without instability after a complete ACL injury. However, some have difficulty performing even simple ADLs because of ACL deficiency-related instability, and they may require surgery.
b. Contraindications
i. Contraindications include lack of quadriceps function, significant comorbidities, or inability to tolerate the surgery.
ii. After an acute injury, patients should not have surgery until they have regained full range of motion (ROM), good quadriceps function, control of effusion, and normal gait. Patients who undergo ACL reconstruction before swelling has been eliminated and full ROM has been reestablished are at higher risk for postoperative arthrofibrosis.
iii. Advanced osteoarthritis is a relative contraindication. Patients with osteoarthritis may have significant pain after the surgery despite a stable knee; therefore, they may not experience a satisfactory outcome.
c. Surgical procedures
i. The most important surgical factor is a well-performed technique, not the specific type of technique.
ii. Graft choices include autologous bone-patellar tendon-bone, autologous hamstring tendons, autologous quadriceps tendon, and allograft tissue. Clinical outcomes appear similar for all.
iii. There is no definitive evidence regarding the superiority of using a bone-patellar tendon-bone autograft versus a hamstring tendon autograft. A bone-patellar tendon-bone autograft may have a lower rerupture rate than a hamstring tendon autograft, but the bone-patellar tendon-bone procedure is associated with more postoperative pain from the donor site and a higher risk of postoperative anterior knee pain, particularly when the patient kneels. In addition, the risk of patella or tibia fracture, although very rare with a bone-patellar tendon-bone autograft procedure, is virtually eliminated when autograft hamstring tendons are used.
iv. During the past few years, there has been a trend toward increasing allograft use in the United States. However, most studies published to date on allograft reconstructions involved an older patient population. In addition, allograft tissue carries a risk of disease transmission.
d. Surgical outcomes
i. Reconstruction of the ACL generally results in excellent outcomes, with most patients returning to their previous level of activity.
ii. Autograft choice and the use of the one- or two-incision technique do not appear to affect outcome.
iii. Rerupture rates vary from 2% to 5%, according to the literature.
iv. Instrumented laxity with KT-1000 arthrometer has demonstrated 75% to 97% of patients have <3 mm of side-to-side difference in laxity.
E. Complications
1. Anesthesia-related complications (eg, pain related to a spinal or epidural block, spinal headache, or major respiratory or allergic problems secondary to general anesthesia) can occur.
2. Deep infection following ACL reconstruction is uncommon (<1%).
a. When it does occur, deep infection may require repeat arthroscopies for irrigation and debridement, as well as possible hardware removal and removal of graft to eradicate the infection.
b. Deep infections involving the knee are generally treated with 6 weeks of intravenous antibiotic therapy.
3. Knee stiffness is generally uncommon and can usually be resolved with physical therapy. It is more common after multiligament reconstructive surgery; in some cases, repeat surgery or manipulation under anesthesia may be required.
4. Thromboembolic disease is uncommon, but patients with a family history for this condition or with hypercoagulability may be considered for anticoagulation.
5. Painful hardware at the proximal tibia near the tibial tunnel can lead to repeat surgery for hardware removal, should this be sufficiently disabling for patients.
6. Loss of full extension can occur secondary to scarring from the graft or if remaining ACL tissue scars and forms a cyclops lesion (which is a scar formed in the intercondylar notch, blocking extension). This can require repeat surgery to remove the tissue that blocks full extension.
F. Revision surgery
1. When evaluating a failed ACL reconstruction, the surgeon must attempt to determine the etiology of failure.
2. Graft failure is classified as biologic, traumatic, or related to technical failure.
3. Revision surgery is more technically demanding due to the existence of prior tunnels and hardware.
4. Allograft tissue is often preferred for revision surgery, because graft tissue is not limited and harvesting from the contralateral leg is not necessary.
5. Outcome following ACL revision surgery appears to be inferior compared with primary reconstruction, although the reason for this is not well documented.
G. Pearls and pitfalls
1. Tunnel placement is the most critical aspect of ACL reconstruction.
2. The most common error in an ACL reconstruction is to place either the tibial or femoral tunnel too anteriorly, leading to graft impingement and failure.
3. When using a single-incision technique, the tibial tunnel should begin at the anterior part of the tibial insertion of the MCL to allow the graft to be placed obliquely and arrive at the 10:30 or 1:30 position on the intercondylar notch of the femur. If the tibial tunnel is placed too anteriorly on the tibia, the graft will be vertically placed, which is not desirable. It is important to understand that the direction of the tibial tunnel influences femoral tunnel placement with the use of a single-incision technique (if the femoral tunnel is drilled through the tibial tunnel). This problem can be avoided by drilling the femoral tunnel through a medial portal.
H. Rehabilitation
1. Studies have shown that a postoperative leg immobilizer is not required after the first day or two.
2. After surgery with modern fixation techniques, patients are allowed to bear weight (ie, stand) as tolerated with crutches. They can then ambulate with the crutches until they can walk normally without them, which is generally 1 month after surgery.
3. Patients then work on closed-chain strengthening and are allowed to start light running between 3 and 4 months if they have progressed sufficiently with strengthening.
4. Return to sports is generally not allowed until 6 months after surgery. For most patients, it is allowed between 6 and 12 months, depending on their rate of progression with rehabilitation.
II. Posterior Cruciate Ligament Injuries
A. Overview and epidemiology
1. The PCL is the primary restraint to posterior tibial translation in the intact knee.
2. It has been previously reported that 5% to 20% of all ligamentous injuries to the knee involve the PCL, and many of these injuries are believed to go undiagnosed in the acutely injured knee.
3. Injuries to the PCL may be isolated or combined with other capsuloligamentous injuries in the knee.
4. Although the diagnosis of a combined PCL injury may be obvious in a knee subjected to high-energy trauma, an isolated PCL injury may be less obvious because instability is often subtle or even asymptomatic.
B. Pathoanatomy
1. A direct blow to the proximal aspect of the tibia is the most common cause of PCL injury.
a. In athletes, the mechanism of injury is usually a fall onto the flexed knee with the foot plantar flexed, which places a posterior force on the tibia and subsequently causes rupture of the PCL.
b. In high-energy trauma, such as motor vehicle accidents, the PCL is often injured with other capsuloligamentous structures.
[
Figure 2. MRI of an acute PCL injury. A, Initial MRI (lateral view) showing PCL injury. B, Follow-up MRI (lateral view) showing healing of the PCL.]
2. When three or more ligamentous structures are injured, the physician should view the injury as a dislocated knee.
3. The natural history of these injuries is not entirely clear, but there is evidence that certain PCL injuries (especially combined) will progress to instability, pain, and osteoarthritis of the knee.
C. Evaluation
1. History
a. The history of the injury helps differentiate between high- and low-energy trauma.
b. Dislocation, neurologic injury, and additional injuries based on mechanism may further assist in the evaluation.
2. Physical examination
a. The physical examination relies heavily on the posterior drawer test; however, the Lachman test for ACL injury, testing for varus and valgus, and testing for external and internal rotation are critical in differentiating between isolated and combined injuries.
b. A knee with an isolated PCL injury will exhibit a positive posterior drawer test at 90°, which translates as >10 to 12 mm in neutral rotation. This will be reduced to 6 to 8 mm of posterior translation when the knee is in internal rotation.
c. On the other hand, in a combined PCL and capsoligamentous injury (ie, when the PCL is injured in conjunction with other structures such as the ACL, posterolateral corner, or medial side), a positive posterior drawer test at 90° will be >15 mm in neutral rotation and >10 mm in internal rotation.
3. Imaging
a. Plain radiographs are important initially, to rule out fractures and avulsions and to ensure that the knee is not dislocated.
b. The key is to recognize that when the knee (intact ACL and PCL) is centered in the sagittal plane, the tibia is anterior to the femoral condyles.
c. MRI complements the history and physical examination, and it helps to determine the site of injury and continuity of the PCL (Figure 2). MRI findings may also influence treatment strategies.
D. Classification
1. PCL injuries do occur in isolation or in combination with other injuries.
2. Types of PCL injuries are listed in
Table 1.
E. Treatment
1. Nonsurgical
[Table 1. Classification of PCL Injuries]
a. Nonsurgical treatment is reserved for isolated PCL injuries or combined PCL injuries in totally noncompliant patients.
b. The PCL can heal in this scenario (Figure 2) if the treatment is relative immobilization (daily ROM exercises for a short period of time) in extension for 1 month followed by rehabilitation, particularly quadriceps strengthening.
2. Surgical
a. Indications—Surgical treatment is indicated for isolated chronic PCL injuries when there are continued instability symptoms (particularly when ascending and descending stairs and inclines), and for combined PCL/capsuloligamentous injuries.
b. Surgical procedures
i. The PCL can be repaired (avulsions) and augmented, or reconstructed.
ii. Reconstruction can be done via a femoral tunnel technique with a tibial inlay (
Figure 3) or a tibial/femoral tunnel technique (
Figure 4).
iii. In addition, single-bundle (anterolateral) or double-bundle (anterolateral/posteromedial) femoral tunnel techniques have been popularized. Allograft tissue is usually utilized for single-bundle and double-bundle reconstructions. Typically, Achilles tendon is used, but bone-patellar tendon-bone, hamstring tendons, and anterior tibialis tendons are viable alternatives.
iv. No clinical outcome studies in the literature clearly support one technique over the other.
[Figure 3. Illustrations of single femoral tunnel PCL reconstruction with tibial inlay using bone-tendon-bone graft. A, Lateral view. B, Posterior view.]
[Figure 4. Illustrations of PCL reconstruction with single tunnel technique in femur and tibia with bone-tendon-bone graft. A, Lateral view. B, Posterior view.]
v. In addition to the one versus two femoral tunnel and the tibial tunnel versus inlay technique controversy, there is controversy about the best tissue for reconstruction.
vi. Graft choices include (1) autologous middle-third patellar tendon-bone; (2) autologous quadriceps tendon-bone; (3) allograft bone-patellar tendon-bone; (4) allograft Achilles tendon-bone; or (5) semitendinosus tendon and gracilis tendon.
vii. Tissue preference is based on training and availability and not on any outcomes study.
F. Complications
1. Patellofemoral pain and/or arthritis (chronic PCL deficiency) can occur as a result of increased dynamic stabilization by the quadriceps.
2. Neurovascular injury can be a devastating complication.
3. Failure to reference the tibia in relation to the femur can lead to misdiagnosis.
G. Pearls and pitfalls—Knee instability occurs less frequently with isolated PCL injuries than it does with ACL injuries.
H. Rehabilitation—Should focus on quadriceps strengthening and reducing patellar pain.
III. Medial Collateral Ligament and Posteromedial Corner Injuries
A. Overview and epidemiology
1. The tibial MCL is the most commonly injured ligament of the knee. The true incidence may be underestimated due to a lack of reporting for lesser grades of injury.
2. Concomitant ligamentous injuries (95% are ACL) occur in 20% of grade I, 52% of grade II, and 78% of grade III injuries.
3. Concurrent meniscal injuries have been noted in up to 5% of isolated medial ligamentous injuries.
B. Anatomy
1. The medial capsuloligamentous complex is comprised of a three-layered sleeve of static and dynamic stabilizers extending from the midline anteriorly to the midline posteriorly (
Figure 5).
2. Static stabilizers
a. The superficial MCL
b. The posterior oblique ligament (POL)
c. The deep MCL (middle capsular ligament)
3. Dynamic stabilizers—The semimembranosus complex (composed of five insertional attachments), the pes anserinus muscle group (the sartorius, gracilis, and semitendinosus muscles), the vastus medialis, and the medial retinaculum provide abduction stability under dynamic conditions.
C. Biomechanics of the medial capsuloligamentous restraints
1. The main function of this complex is to resist valgus and external rotation loads.
2. The superficial MCL is the primary restraint to valgus loads.
3. Posterior oblique, deep medial collateral, and cruciates are secondary restraints to valgus stress.
[Figure 5. Illustration of the static and dynamic stabilizers of the medial and posteromedial aspects of the knee.]
D. Evaluation
1. History
a. Lesser degrees of MCL sprains result from a noncontact valgus, external rotation force. Complete disruption usually results from a direct blow to the lateral aspect of the knee.
b. Occasionally, a "pop" is noted by the patient.
c. The ability to ambulate and/or continue to participate in athletic activities depends on the degree of disruption, the player's position, and the presence of any concurrent injuries.
2. Physical examination
a. The knee should be inspected for ecchymosis, localized tenderness, and the presence of an effusion.
b. Abduction stress testing should be performed with the knee at 0° and 30° of flexion.
c. The superficial MCL is isolated with a valgus stress at 30° of flexion.
i. Pathologic laxity is indicated by the amount of increased medial joint-space separation compared to the opposite, normal knee (Grade I: 1 to 4 mm; Grade II: 5 to 9 mm; Grade III: ≥10 mm).
ii. Valgus laxity with the knee at or near full extension implies concurrent injury to the posteromedial capsule and/or cruciate ligaments.
iii. Summary MCL evaluation
(a) If stable in 0° of extension, then either grade I or II (nonsurgical treatment)
(b) If increased laxity at 0°, then grade III with injury posteromedial (consider ACL or PCL combined injury)
d. Evaluation of associated and other injuries
i. The Lachman and anterior drawer tests should be performed to rule out an ACL injury.
ii. The pivot-shift test is often falsely negative in the presence of a grade III MCL sprain.
iii. A PCL injury is assessed by palpation of the tibial-condylar step-off and posterior drawer test (both performed at 90° of flexion), the quadriceps-active test, and observation of posterior tibial sag.
iv. Patellar apprehension and tenderness over the patella and medial retinaculum indicate possible patellar dislocation.
v. Diagnosis of an isolated medial meniscal injury is suggested by medial joint-line tenderness, the absence of pain to valgus stress, and increased pain on flexion-rotation testing (McMurray test).
3. Imaging
a. Plain radiographs are typically normal but should be inspected for fractures, lateral capsular avulsion (Segond fracture), and Pellegrini-Stieda lesion (indicative of prior MCL injury).
b. Stress radiographs may be indicated in skeletally immature individuals to rule out a physeal injury.
c. MRI has become the imaging modality of choice to evaluate the injured MCL.
i. The advantages of MRI are that it identifies the location and extent of injury, and it is useful in ruling out associated meniscal, chondral, and cruciate injuries.
ii. The disadvantages of MRI are that it is expensive, reader-dependent, and may overestimate the degree of injury.
E. Classification—Sprains of the MCL are classified based on the extent of ligamentous disruption and resulting degree of patholaxity (
Table 2).
F. Treatment
1. Nonsurgical
a. Indications
i. All isolated grade I and II injuries
ii. Grade III injuries that are stable in extension without associated cruciate injury
b. Contraindications
i. Gross laxity to valgus stress at 0° and sometimes 30° of flexion, which implies concurrent ligamentous and/or capsular damage to ACL or PCL (combined injury).
ii. A grade III injury with the ligament displaced into the joint
c. Procedures/treatment protocol
i. Crutches, ice, compression, elevation, and anti-inflammatory/pain medication are initiated.
ii. No brace is usually required for grade I injuries; crutches can be used as necessary. A knee immobilizer (comfort) or hinged brace (for walking) is recommended for grade II and grade III injuries.
iii. Quadriceps setting and straight-leg raises are initiated immediately for all injuries.
iv. Cycling and progressive resistance exercises are started when tolerated.
v. Thigh adduction exercises should be performed above the level of the joint line.
vi. A low-profile, open-hinged brace is used for grade II and III injuries as activity improves and for a return to sports.
d. Complications
i. Proximal injuries are associated with difficulty obtaining full motion. Distal injuries are associated with residual laxity.
ii. Asymptomatic residual laxity is typically seen following the conservative treatment of grade II and III injuries.
iii. Residual rotatory knee instability during cutting and pivoting activities is seen when there is an unrecognized ACL injury.
iv. A Pellegrini-Stieda lesion (calcification at the femoral origin of the MCL) is common and may become tender from direct pressure over the bony mass.
e. Pearls and pitfalls
i. Grade I injuries result in the production of minimal swelling or effusion; the presence of a large effusion implies a grade II injury and/or concurrent ligamentous or cartilaginous injury. Grade III injuries are associated with disruption of the joint capsule that allows any accumulated effusion to leak into the soft tissues, resulting in only a small palpable effusion.
ii. MRI is indicated for a significant effusion, an inconclusive cruciate examination, or suspicion of a concurrent meniscal or cartilaginous injury.
iii. Timing of return to sports is directly related to the degree of injury: Grade I injuries, 5 to 7 days; grade II injuries, 2 to 4 weeks; grade III injuries, 4 to 8 weeks.
iv. Timing of ACL reconstruction with a concurrent MCL injury should be delayed proportional to the degree of MCL injury to allow for ligamentous healing. A rough estimate is as follows: Grade I injuries, 3 to 4 weeks; grade II injuries, 4 to 6 weeks; grade III injuries, 6 to 8 weeks.
f. Rehabilitation—Rehabilitation activities are progressed based on the athlete's ability to reach specific milestones: jogging, agility drills, sport-specific drills, and return to sports. The athlete should be pain-free during these activities before progressing to the next level.
2. Surgical
a. Indications
i. Isolated grade III injuries with persistent instability despite attempted supervised rehabilitation and bracing
[Table 2. Classification of MCL Sprains*]
ii. Grade III injuries with valgus laxity in full extension (>10 mm of medial joint-space opening)
iii. Ligament entrapment within the medial compartment
iv. Chronic valgus instability with associated cruciate deficiency
v. Grade III injuries with PCL, or ACL/PCL combined injuries
b. Contraindications
i. All grade I and grade II injuries
ii. Grade III injuries stable to valgus stress in full extension
c. Surgical procedures—Acute repair
i. Diagnostic arthroscopy is recommended to rule out associated damage.
ii. Ligament avulsions should be reattached with suture anchors with the knee at 30° of flexion.
iii. Interstitial disruption warrants attachment of the MCL to its femoral and tibial origins with anterior advancement.
iv. Once the MCL is repaired, the POL is advanced anterosuperiorly to the adductor tubercle and distally to the tibial metaphysis.
d. Surgical procedures—Chronic reconstruction
i. If sufficient tissue remains, proximal advancement of the femoral origin of the MCL with attached bone block and advancement of the POL is recommended.
ii. If insufficient local tissue remains, a semitendinosus autograft may be used to reconstruct the superficial MCL with isometric fixation using a screw and washer to the medial epicondyle. Allograft hamstring, tibialis anterior, or Achilles tendon may also be used for chronic instability.
e. Complications
i. Loss of motion (flexion and extension) is the most common complication following surgical treatment.
ii. Injury to the saphenous nerve may be temporary (neurapraxia) if it is stretched, or permanent (axonotmesis) if it is cut.
f. Pearls and pitfalls
i. MRI can be useful in planning a limited surgical exposure based on the location of injury (proximal or distal).
ii. For primary repair, knee motion should be checked after the placement of each suture. Limitation of motion or suture disruption indicates nonisometric suture placement.
IV. Lateral Collateral Ligament and Posterolateral Corner Injuries
A. Overview and epidemiology
1. Injuries to the lateral collateral ligament (LCL) and posterolateral compartment are reported less commonly than injuries to the medial side of the knee, in part due to lack of recognition.
2. Between 7% and 16% of all knee ligament injuries are to the lateral ligamentous complex.
B. Anatomy
1. The lateral compartment of the knee is supported by both dynamic and static stabilizers (
Figure 6).
a. The dynamic stabilizers consist of the biceps femoris, the iliotibial band, the popliteus muscle, and the lateral head of the gastrocnemius muscle.
b. The static ligamentous (arcuate) complex consists of the fibular (lateral) collateral ligament, the popliteus tendon, and the arcuate ligament.
2. The lateral capsular complex of the lateral aspect of the knee is divided into thirds.
a. The anterior third attaches to the lateral meniscus anterior to the LCL.
b. The middle third attaches proximally at the femoral epicondyle and distally at the proximal tibia.
c. The posterior third is located posterior to the LCL.
C. Biomechanics of the lateral capsuloligamentous restraints
1. The LCL is the primary restraint to varus stress at 5° and 25° of knee flexion, providing 55% of restraint at 5° and 69% at 25°.
2. The popliteus restricts posterior tibial translation, external tibial rotation, and varus rotation.
[Figure 6. Illustration of the static and dynamic stabilizers of the lateral and posterolateral aspects of the knee.]
D. Evaluation
1. History
a. Injuries to the lateral ligament of the knee most frequently result from motor vehicle accidents and athletic injuries.
b. Lateral ligament injuries result from either a direct blow or force to the weight-bearing knee, resulting in excessive varus stress, external tibial rotation, and/or hyperextension.
c. A posterolaterally directed force to the medial tibia with the knee in extension is the most common mechanism.
d. Combined injury to the cruciates is more common than isolated injury to the lateral and posterolateral structures.
e. Instability in the active patient is most commonly noted with the knee near full extension. Patients may experience difficulty ascending and descending stairs as well as with cutting or pivoting activities.
f. Patients may report lateral joint-line pain.
2. Physical examination
a. Adduction stress is performed at both 0° and 30° of knee flexion.
i. Isolated laxity at 30° is consistent with injury to the LCL.
ii. Laxity at both 0° and 30° is seen with additional injury to the ACL, PCL, or arcuate complex.
b. The posterolateral drawer test is specific for rotatory injury to the posterolateral corner.
i. This test should be performed at both 30° and 90° of flexion.
ii. A positive test at 30° is most consistent with posterolateral injury.
iii. A more pronounced test at 90° of flexion implies an associated PCL injury.
c. The Dial test, performed at 30° of flexion, is considered positive when the involved foot and ankle exhibit >10° of external rotation compared with the normal side.
d. The external recurvatum test is performed with the examiner lifting the great toes of both feet with the knees in full extension. A positive test is indicated by both lateral knee hyperextension and external tibial rotation.
e. In the reverse pivot-shift test, the knee is taken from flexion to extension with the foot held in external rotation while a valgus force is applied. With a positive test, the tibia reduces with a shift or jump from its posteriorly subluxated position at 20° to 30° of flexion.
f. With chronic injuries, an evaluation of gait is important to detect the presence of a varus or hyperextension thrust.
g. Neurovascular injuries (eg, common peroneal nerve injuries in the LCL and posterolateral corner, and popliteal vascular structure injuries in knee dislocation) are associated with patterns of knee ligament injuries. Evaluation of neurovascular structures is imperative, as up to 29% of patients with acute posterolateral corner injuries have peroneal nerve deficits.
3. Imaging
a. Plain radiographs should be obtained for all patients with suspected injury to the posterolateral corner, to rule out an associated osteochondral fracture, fibular head avulsion, Gerdy tubercle avulsion, or fracture of the tibial plateau.
i. A Segond fracture (lateral capsular avulsion) is often seen with an ACL injury.
ii. Chronic posterolateral instability may show lateral tibiofemoral or patellofemoral degenerative changes.
b. MRI is the imaging modality of choice to evaluate the status of the LCL, popliteus tendon, and cruciate ligaments. MRI will provide information about the severity (mild sprain versus complete tear) and location (avulsion versus midsubstance tear) of injury.
E. Classification
1. Instability can be defined as either straight or rotatory, depending on the degree of associated patholaxity.
a. Isolated injury to the LCL resulting in coronal plane laxity (straight instability) is rare.
b. Rotatory instability resulting in multiplanar laxity is seen with combined injury to the LCL and either the ACL and mid-third capsular ligament (anterolateral instability) or arcuate ligament, popliteus tendon, and fabellofibular ligament (posterolateral instability).
c. Combined instability patterns may occur either as acute or chronic injuries. Chronic, isolated injury to the LCL is rare, as most patients with chronic injury to the LCL eventually develop associated injury patterns involving the posterolateral corner structures.
2. Posterolateral corner injuries are often classified as grade I, II, or III sprains, depending on if there is minimal, partial, or complete ligament disruption.
[
Table 3. Classification of Posterolateral Corner Injuries*]
3. A more accurate classification is based on the quantification of lateral joint opening (as compared with the normal contralateral knee) with varus stress (Table 3).
F. Treatment
1. Nonsurgical
a. Nonsurgical treatment of ligamentous injuries to the lateral side of the knee is limited to partial (grade I and II) isolated injuries of the LCL without involvement of the arcuate complex. These patients have little functional instability, especially if they possess valgus knee alignment.
b. Nonsurgical treatment consists of limited immobilization with protected weight bearing for the first 2 weeks. Progressive ROM, quadriceps strengthening, and functional rehabilitation are then initiated as tolerated.
c. Contraindications to nonsurgical treatment include complete (grade III) injuries or avulsions of the LCL and combined rotatory instabilities involving the LCL and posterolateral compartment structures.
d. The most common complication of nonsurgical treatment of these injuries is progressive varus/hyperextension laxity due to unrecognized associated injuries to the posterolateral structures.
e. Return to sports can be expected in 6-8 weeks.
2. Surgical
a. Indications
i. Complete injuries or avulsions of the LCL
ii. Rotatory instabilities involving the LCL and arcuate ligament, popliteus tendon, and fabellofibular ligament
iii. Combined instability patterns involving the LCL/posterolateral corner and ACL or PCL
b. Surgical procedures—Acute injuries
i. Surgical options for acute injuries include primary repair of torn or avulsed structures and reconstruction if the native tissue is of insufficient quality.
ii. Surgery is usually recommended within 2 weeks of injury to prevent the formation of scar tissue and distortion of tissue planes that could hinder a direct repair.
iii. Arthroscopy is recommended to assist in the diagnosis of all torn structures as well as any meniscal or chondral injuries.
iv. Suture anchors can be used to repair avulsed structures.
v. Direct suture repair can be used for midsubstance injuries.
c. Surgical procedures—Chronic LCL and posterolateral corner insufficiency. Allograft tissue has been used to form either a single-stranded graft (bone-patellar tendon-bone) to reconstruct isolated LCL injuries, or a bifid graft (Achilles tendon) to anatomically reconstruct multiple injured structures including the LCL, popliteus, and popliteofibular ligament.
d. Complications
i. Persistent varus or hyperextension laxity is often seen with advancement of attenuated lateral and posterolateral structures in chronic injuries.
ii. Injury to the peroneal nerve can occur during surgical exposure of the fibular neck, or during drilling or graft passage through a transfibular tunnel.
iii. Loss of knee motion usually occurs with the reconstruction of multiple ligaments, especially the ACL.
iv. Hardware irritation most commonly occurs at the lateral femoral condyle.
G. Pearls and pitfalls
1. The results of surgery performed acutely have a more favorable outcome than surgery performed for chronic laxity.
2. All ligamentous deficiencies should be addressed to prevent persistent rotatory instability.
3. Previously described methods of anterior femoral advancement (Hughston procedure) or recession of the attenuated arcuate complex are no longer recommended for chronic instability.
4. Use of the biceps femoris as a reconstructive graft in chronic posterolateral instability should be discouraged, because it does not prevent external tibial rotation and it eliminates the biceps as a dynamic lateral stabilizer of the knee.
5. Ligamentous reconstruction of the LCL should involve placement of graft tissue directly to the fibular head rather than to the lateral tibia to optimize graft isometricity.
6. Identification of the peroneal nerve is best done just posterior to the fibular head and then traced proximally.
7. Long-leg casting is recommended for the first 4 postoperative weeks to prevent external tibial rotation that may occur with the use of a simple hinged knee brace.
8. Full-length upright radiographs of both lower extremities should be obtained for all patients with chronic instability to assess for the presence of varus mechanical axis. In these cases, a high tibial osteotomy is recommended before ligamentous reconstruction.
V. Multiligament Knee Injuries
A. Overview and epidemiology
1. Multiligament knee injuries are usually caused by high-energy trauma and are often considered knee dislocations.
2. Less frequently, low-energy trauma or ultra-low-velocity trauma in obese patients can also result in this injury pattern.
3. A bicruciate injury or a multiligament knee injury involving three or more ligaments should be considered a spontaneously reduced knee dislocation.
4. A knee dislocation should be considered a limb-threatening injury, and careful monitoring of vascular status after the injury is imperative.
B. Pathoanatomy
1. Multiligament knee injuries most frequently involve a partial or complete rupture of both cruciate ligaments.
2. Rare cases of knee dislocation have been reported with one cruciate intact.
3. Most commonly, either the medial or lateral side of the knee will also be injured.
4. When high-energy trauma is involved, occasionally both medial and lateral-sided injuries can accompany the bicruciate injury.
5. Popliteal artery (estimated at 32%) or peroneal nerve injury (20% to 40%) also can occur.
6. Extensor mechanism injury (quadriceps or patellar tendon) or patellar dislocation also is encountered in this injury pattern.
7. Associated fractures can complicate management of the multiligament-injured knee, and definitive fixation of unstable fractures should be performed first in a staged fashion or concomitantly with any ligament surgery.
C. Evaluation
1. History
a. A high index of suspicion for a reduced knee dislocation should accompany any knee injury that involves three or more ligaments.
b. Mechanism of injury, position of the knee when it was injured, and timing of the injury are all important historic factors.
c. A history of previous knee injury and current function are also relevant, as are age, activity level, and previous surgery or other injuries.
2. Physical examination
a. Vascular examination is critical in an acutely dislocated knee.
i. Pulse and ankle-brachial index (ABI) should be carefully assessed. An ABI of less than 0.90, and most certainly less than 0.80, should be considered abnormal.
ii. If there is any concern about an abnormal vascular examination, there should be a low threshold for ordering an angiogram.
iii. If pulses are still abnormal or absent following reduction of the dislocation, immediate vascular surgery consultation with intraoperative exploration should be the next step in management.
iv. A vascular injury in a knee dislocation (estimated at approximately 32%) is a limb-threatening injury and needs to be corrected within 6 to 8 hours. If not corrected, amputation may be required.
b. Neurologic examination is also critical, as peroneal nerve injury can occur with multiligament injuries, particularly in concomitant lateral/posterolateral corner injuries.
c. Swelling should be assessed.
d. A patellar examination should be conducted to assess extensor mechanism integrity and stability.
e. ROM should be determined.
f. Stability testing is critical, including anterior and posterior drawer tests, posterior sag test, Lachman test, varus and valgus testing at 0° and 30°, and Dial testing at 30° and 90°.
g. Assessment of gait and pivot and reverse pivot-shift testing can be performed in more chronic multiligament injuries.
3. Imaging
a. Plain radiographs are an essential part of the initial evaluation of multiligament knee injuries.
[
Figure 7. MRI of a KDIIIL acute multiligament knee injury in a college football quarterback. A, T2-weighted coronal image showing the lateral and posterolateral corner structures avulsed off the posterolateral tibia and fibular head with proximal retraction. B, T1-weighted sagittal view showing a bicruciate ligament injury.]
i. Associated fractures, including fibular head or PCL tibial plateau avulsions, may affect the timing of surgery, and early open reduction and internal fixation of these fractures may improve healing.
ii. In chronic multiligament-injured knees, standing long-cassette alignment films should be obtained to evaluate lower limb alignment.
iii. Often, radiographs can reveal posterior tibial subluxation on lateral views or medial or lateral joint-space widening on AP or PA views.
b. MRI—When evaluating a multiligament-injured knee, MRI is useful for determining the site and extent of ligament injuries (eg, distal versus proximal for collaterals or avulsions for cruciates) (Figure 7). This is particularly useful in severe injuries, as physical examination is often difficult due to significant pain and guarding.
D. Classification is based on the direction of dislocation and the anatomic area of injury.
1. Direction of dislocation (direction of tibia displacement)
a. Anterior, posterior, lateral, medial, posterolateral
b. Posterolateral dislocations are often irreducible as a result of the medial femoral condyle buttonholing through the medial capsule, causing the "dimple" sign.
2. Anatomic classification of knee dislocations is shown in
Table 4.
E. Treatment—In the multiligament-injured knee that presents as a knee dislocation, emergent closed reduction and splinting or bracing should be performed immediately. Postreduction radiographs should be taken to confirm knee reduction.
1. Nonsurgical
a. Indications
i. With current reconstructive techniques, non-surgical management of multiligament injuries is usually reserved for elderly low-demand patients, patients who have comorbidities that would make surgical risks greater, or patients who have concomitant injuries (including vascular injuries, head injuries, compartment syndrome, or associated fractures).
ii. Desire for nonsurgical management
iii. Partial or incomplete multiligament injuries resulting in reasonable knee stability
b. Contraindications
i. Nonsurgical treatment is contraindicated in the presence of the comorbidities or concomitant injury patterns described above (irreducible dislocations, neurovascular injuries).
ii. Despite these contraindications, surgical stabilization may still be pursued in a staged fashion after healing of associated fractures or vascular repair or bypass.
c. Complications
i. Persistent knee instability
ii. Knee stiffness or loss of motion (if motion is restricted for extended periods of time as part of the nonsurgical management protocol)
d. Pearls and pitfalls
i. Treatment should include a relatively short period of immobilization in full extension followed by protected ROM, preferably in a hinged knee brace to provide varus/valgus stability.
ii. Treatment should include patellar mobilizations to prevent patellar entrapment and the development of arthrofibrosis.
iii. Careful monitoring of gait, to avoid chronic dynamic instability patterns such as a varus thrust, is important.
iv. If fractures require skeletal stabilization, this care should be carefully coordinated with the trauma team to ensure appropriate placement of incisions for future planned ligament stabilization.
v. If vascular repair is necessary, a consultation with the vascular surgery team about planned incisions, timing of future ligament reconstructions, and motion limitations should be initiated.
e. Complications, including persistent knee instability, arthrofibrosis, and gait abnormalities, such as a fixed varus deformity or dynamic varus thrust, can occur.
2. Surgical
a. Indications
i. Injury of two or more ligaments (definition of multiligament injury) that result in an unstable knee
ii. Inability to perform ADLs without knee instability
iii. Ability to comply with the postoperative rehabilitative protocol
iv. Associated fractures requiring stable fixation
v. Emergent surgical indications: irreducible knee dislocation requiring open reduction, open dislocation, vascular injury, or compartment syndrome.
b. Contraindications
i. Urgent concomitant injuries that preclude surgical reconstruction or repair of injured ligaments such as vascular injury, compartment syndrome, certain associated fractures (can sometimes be done together), open injuries, or head injuries
[Table 4. Anatomic Classification of Knee Dislocations]
ii. Inability to comply with the postoperative rehabilitative protocol
iii. Other medical comorbidities that preclude surgery such as unstable coronary artery disease
3. Surgical procedures
a. There are many approaches to the surgical management of multiligament-injured knees.
b. There is no high level of evidence available at the current time to make any definitive recommendations on surgical management.
c. Controversies about the optimal surgical management of multiligament injuries that are currently being argued and debated include:
i. Timing: Acute (restore knee stability early, allowing for early protected ROM) versus delayed (regain motion, allow swelling and inflammation to subside)
ii. Type of graft: Autograft (improved healing of grafts and ligamentization) versus allograft (decreased morbidity given large number of structures requiring reconstruction)
iii. Surgical approach: Open (improved visualization and no risk of arthroscopic fluid-induced compartment syndrome) versus arthroscopic (decreased morbidity)
iv. Which ligaments: Reconstruct all ligaments (restore knee stability early, allowing for early protected ROM) or reconstruct certain ligaments and perform staged reconstructions (gradual restoration of knee stability while limiting morbidity from each procedure and allowing restoration of motion)
v. Repair (refers to medial and lateral-sided acute injuries, usually within 2 to 3 weeks) versus reconstruction of torn ligaments (refers to the ACL, PCL, or delayed reconstruction or augmentation of medial or lateral repairs for added stability)
vi. Early protected motion (regain early motion) versus initial immobilization (protect healing of reconstructed or repaired ligaments)
vii. Initial stabilization with brace (would allow early protected ROM, but fixed posterior subluxation may occur) versus external fixation (allows anatomic reduction of tibiofemoral joint, but arthrofibrosis may lead to significant ROM problems and pin tracks may get in the way of future planned ligament surgery), particularly in cases of vascular injury or need for nonsurgical management or delayed surgical reconstruction due to the presence of surgical contraindications
d. Complications
i. Arthrofibrosis with loss of motion
ii. Recurrent instability
iii. Infection
iv. Neurovascular injury including injury to the popliteal artery or peroneal nerve injury
e. Pearls and pitfalls
i. The available literature suggests that earlier reconstruction may improve outcomes when compared with outcomes for chronically reconstructed knees.
ii. If a lateral-sided injury occurs, acute repair and/or reconstruction is recommended, preferably within 2 weeks of injury and certainly within 3 weeks. With repairs later than 3 weeks, the lateral/posterolateral structures are often scarred and retracting, which often necessitates a concomitant reconstruction.
iii. If performing arthroscopy during the multiligament knee surgery, be very careful about pump pressure and watching the leg compartments for fluid extravasation and possible compartment syndrome. Often, it is advisable to wait 7 to 10 days to allow the capsular injury often associated with multiligament knee injuries to heal and to use gravity flow.
iv. Watch carefully for foot/ankle contractures in patients with peroneal nerve injuries.
v. Missed posterolateral corner injuries have been associated with both failed ACL and PCL surgery. A high index of suspicion for these injuries should accompany any bicruciate or PCL ligament injury.
vi. Early protected motion is usually recommended, because arthrofibrosis is a common occurrence following surgical reconstruction. However, this should be carefully monitored, because recurrent laxity or instability can complicate an aggressive rehabilitation protocol. A closely supervised rehabilitation protocol is advisable.
Top Testing Facts
1. An effusion after knee injury is related to hemarthrosis and is secondary to bleeding from the vascular, torn ligament.
2. MRI evidence of a bone bruise pattern in the area of the anterior lateral femoral condyle and the posterior lateral tibial plateau is pathognomic of ACL injury.
3. The most important surgical factor is a well-performed technique, not the specific type of technique.
4. The most common error in an ACL reconstruction is to place either the tibial or femoral tunnel too anteriorly, leading to graft impingement and failure.
5. Grade I and II MCL injuries that are stable in 0° of extension are treated nonoperatively.
6. Valgus laxity with the knee at or near full extension implies concurrent injury to the posteromedial capsule and/or cruciate ligaments.
7. Increased external rotation of the tibia at 30° but not at 90° suggests a posterolateral corner injury.
8. Increased external rotation of the tibia at both 30° and 90° is associated with injury to both the PCL and posterolateral corner.
9. Neurovascular injuries (eg, common peroneal nerve injuries in the LCL and posterolateral corner, and popliteal vascular structure injuries in knee dislocation) are associated with patterns of knee ligament injuries.
10. A bicruciate injury or a multiligament knee injury involving three or more ligaments should be considered a spontaneously reduced knee dislocation. Knee dislocation is a limb-threatening injury requiring careful monitoring of vascular status.
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