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Updated: 2/7/2023

Posterolateral Corner Injury

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Images injury_moved.jpg stress radiograph.jpg poplitues fluid_moved.jpg
  • Summary
    • Posterolateral corner (PLC) injuries are traumatic knee injuries that are associated with lateral knee instability and usually present with a concomitant cruciate ligament injury (PCL > ACL).
    • Diagnosis can be suspected with a knee effusion and a positive dial test but MRI studies are required for confirmation.
    • Treatment is generally operative reconstruction of the PLC complex and the associated ligamentous injuries when present.
  • Epidemiology 
    • Incidence
      • Approximately 7-16% knee ligament injuries are to the posterolateral ligamentous complex
        • only 28% of all PLC injuries are isolated
          • usually combined with cruciate ligament injury (PCL > ACL)
        • missed PLC injury diagnosis is common cause of ACL reconstruction failure
  • Etiology
    • Mechanisms
      • blow to anteromedial knee
      • varus blow to flexed knee
      • contact and noncontact hyperextension injuries
      • external rotation twisting injury
      • knee dislocation
    • Associated injuries
      • common peroneal nerve (15-29%)
      • vascular injury
  • Anatomy
    • Posterolateral corner structures
      • three major static stabilizers of the lateral knee
        • lateral collateral ligament (LCL)
          • most anterior structure inserting on the fibular head
          • primary varus stabilizer of the knee
        • popliteus tendon (PLT)
        • popliteofibular ligament
          • originates at the musculotendinous junction of the popliteus
          • anterior and posterior divisions
      • other static stabilizers
        • lateral capsule thickening
          • meniscofemoral and meniscotibial ligaments
        • arcuate ligament (variable)
        • fabellofibular ligament (variable)
      • dynamic structures
        • biceps femoris
          • inserts on the posterior aspect of the fibula posterior to LCL
        • popliteus muscle
        • iliotibial band (ITB)
        • lateral head of the gastrocnemius
    • Function
      • popliteus works synergistically with the PCL to control external tibial rotation, varus, and posterior tibial translation
      • popliteus and popliteofibular ligament function maximally in knee flexion to resist external rotation
      • LCL is primary restraint to varus stress at 5° (55%) and 25° (69%) of knee flexion
    • Definitions
      • arcuate complex includes the static stabilizers: LCL, arcuate ligament, and popliteus tendon
      • Lateral Structures of Knee by Layer
      • Layer 1
      • Iliotibial tract, biceps
      •      common peroneal nerve lies between layer I and II
      • Layer 2
      • Patellar retinaculum, patellofemoral ligament
      • Layer 3
      • superficial:LCL, fabellofibular ligament
      •          lateral geniculate artery runs between deep and superficial layer
      • deep: arcuate ligament, coronary ligament, popliteus tendon, popliteofibular ligament, capsule
  • Classification
    • Modified Hughston classification
      • Modified Hughston classification
      • Examination
      • Findings
      • Grade I
      • 0-5 mm of lateral opening on varus stress
      •  0°-5° rotational instability on dial test
      • Sprain, no tensile failure of capsuloligamentous structures
      • Grade II
      • 6-10 mm of lateral opening on varus stress
      • 6°-10° rotational instability on dial test
      • Partial injuries with moderate ligament disruption
      • Grade III
      • > 10 mm of lateral opening on varus stress, no endpoint
      •  > 10° rotational instability on dial test, no endpoint
      • Complete ligament disruption
  • Presentation
    • Symptoms
      • often have instability symptoms when knee is in full extension
        • difficulty with reciprocating stairs, pivoting, and cutting
    • Physical exam
      • gait exam
        • standing varus alignment
        • varus thrust or hyperextension thrust with ambulation
      • varus stress
        • varus laxity at 0° indicates both LCL and cruciate (ACL or PCL) injury
        • varus laxity at 30° indicates LCL injury
      • dial test
        • > 10° external rotation asymmetry at 30° only consistent with isolated PLC injury
        • > 10° external rotation asymmetry at 30°and 90° consistent with PLC and PCL injury
      • external rotation recurvatum
        • positive when lower leg falls into external rotation and recurvatum when leg suspended by toes in supine patient
        • only identify ~10% of PLC injuries
        • more consistent with combined ACL and PLC injuries
      • posterolateral drawer test
        • performed with the hip flexed 45°, knee flexed 80°, and foot is ER 15°.
        • a combined posterior drawer and external rotation force is then applied to the knee to assess for an increase in posterolateral translation (lateral tibia externally rotates relative to lateral femoral condyle)
      • reverse pivot shift test
        • knee positioned at 90° and external rotation and valgus force applied to tibia
        • as the knee is extended the tibia reduces with a palpable clunk
          • tibia reduces from a posterior subluxed position at ~20° of flexion to a reduced position in full extension (reduction force from IT band transitioning from a flexor to an extensor of the knee)
      • peroneal nerve injury
        • altered sensation to dorsum of foot and weak ankle dorsiflexion
        • approximately 25% of patients have peroneal nerve dysfunction
  • Imaging
    • Radiographs
      • may see avulsion fracture of the fibula (arcuate fracture ) or femoral condyle
      • stress radiographs
        • bilateral varus stress XR in 20° flexion
        • side-to-side difference 2.7-4 mm = isolated LCL tear
        • side-to-side difference > 4 mm = PLC injury
      • long-leg standing radiographs to evaluate alignment
        • required in cases of chronic PLC injury
        • evaluate for triple varus alignment
          • primary varus = tibiofemoral malalignment
          • secondary varus = LCL deficiency with increased lateral opening
          • triple varus = remaining PLC deficient, overall varus recurvatum alignment
        • necessary to determine mechanical axis and if a proximal tibial osteotomy is necessary for correction
    • MRI
      • look for injury to the LCL, popliteus, and biceps tendon
      • in acute injury may see bone bruising of medial femoral condyle and medial tibial plateau
      • coronal oblique thin-slice through the fibular head are best at visualizing the PLC structures
  • Treatment
    • Nonoperative
      • knee immobilization in full extension x4 weeks, then rehabilitation
        • indications
          • grade I PLC injury
          • isolated midsubstance grade II injury
        • technique
          • hinged knee brace locked in extension x4 weeks
          • followed by progressive functional rehabilitation
          • quad strengthening
          • return to sports in 8 weeks
    • Operative
      • PLC repair
        • indications
          • isolated acute grade II PLC avulsion injuries
            • midsubstance repair have 40% failure rate following repair
        • techniques
          • repair of LCL, popliteus tendon and/or popliteofibular ligament should be performed if structures can be anatomically reduced to their attachment site
            • otherwise perform reconstruction
          • augment PLC repair with free graft if repair tenuous
          • avulsion fracture of fibular head can be treated with screws or suture anchors
      • PLC hybrid reconstruction and repair
        • indications
          • grade III midsubstance injuries
          • avulsion injuries where repair is not possible or tissie is poor quality
        • techniques
          • goal is to reconstruct LCL and the popliteofibular ligament using a free tendon graft (semitendinosus or achilles)
          • fibular-based reconstruction (Larson)
            • soft tissue graft passed through bone tunnel in fibular head
            • limbs are then crossed to create figure-of-eight and fixed to lateral femur to a single tunnel
          • trans-tibial double-bundle reconstruction
            • split achilles tendon is fixed to isometric point of the femoral epicondyle
            • one tibia-based limb and one fibula-based limb
            • fibula-limb is fixed to the fibular head with a bone tunnel and transosseous sutures to reconstruct the LCL
            • tibia-limb is brought through the posterior tibia to reconstruct the popliteofibular ligament
          • LaPrade anatomic reconstruction
            • two soft tissue grafts
            • graft #1 reconstructs the LCL and PFL
              • proximal attachment site at anatomic femoral LCL attachment
              • through the fibular head lateral to medial
              • docking into the tibial tunnel posterior to anterior with graft #2
            • graft #2 reconstructs the popliteus tendon
              • proximal attachment site at the anatomic popliteus tendon attachment
              • docking into the tibial tunnel posterior to anterior with graft #1
        • rehabilitation
          • hinged knee brace, nonweightbearing for 6 weeks
          • range of motion protocols differ between surgeons
            • some advocate for passive ROM immediately 0-90°
            • others immobilize for 2 weeks, then begin motion
          • at 6 weeks, begin weightbearing and closed-chain strenghtening
          • return to activities / sports ~ 6 to 9 months
        • outcomes
          • operative treatment has improved outcomes compared to nonoperative treatment
          • repair has higher failure rate than reconstruction
            • particularly for midsubstance injuries, but also for soft tissue avulsions
          • improved outcomes with early treatment
          • anatomic reconstruction restores rotatory stability, but not all varus stability on stress testing
      • PLC reconstruction, +/- ACL reconstruction, +/- PCL reconstruction, +/- HTO
        • indications
          • acute and chronic combined ligament injuries
        • technique
          • PLC reconstruction should be performed at same time or prior to (as staged procedure) ACL or PCL to prevent early cruciate failure
          • valgus high tibial osteotomy
            • indicated in patients with varus mechanical alignment
            • failure to correct bony alignment jeopardizes ACL and PLC reconstruction success
        • rehabilitation
          • postoperatively immobilize and make protected weight bearing for 4 weeks (long leg casts may control leg external rotation better than brace)
          • begin passive ROM at 4 weeks to avoid arthrofibrosis.
          • avoid active hamstring exercises as they will stress the PLC
          • full active extension is allowed
        • outcomes
          • reconstructions have less revision rates and better outcome scores than ligament repair
            • ACL reconstruction + PLC repair 33% achieved IKDC grade A or B compared to 88% of patients who underwent ACL + PLC reconstruction
  • Complications
    • Arthrofibrosis
    • Missed PLC injury
      • failure to identify a PLC injury will lead to failure of ACL or PCL reconstruction
    • Peroneal nerve injury (15-29%)
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Questions (12)
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(OBQ10.139) A 37-year-old male presents with continued knee pain and instability 6 months status-post combined ACL and PCL reconstruction after a traumatic knee injury. On physical exam his ACL and PCL are intact, however he is noted clinically to have Grade 3 posterolateral corner laxity and varus malalignment of his knee. What is next most appropriate step in management?

QID: 3227

Obtain long leg alignment films for pre-op planning



Fibular based posterolateral corner reconstruction



Combined tibial-fibular based posterolateral corner reconstruction



Physical therapy with closed chained quadriceps exercises, and avoidance of active hamstring exercises



Dynamic functional knee bracing



L 3 C

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(OBQ10.262) A 24-year-old male is involved in a motorcycle accident and sustains a right knee injury. Physical examination manuever performed at 30 degrees of knee flexion is shown in Figure A. Which of the following correctly describes the normal anatomic orientation of the region injured in this patient?

QID: 3313

Popliteus inserts proximal to the LCL on the femur



Posterior oblique ligament originates from the adductor tubercle, just posterior and proximal to the medial collateral ligament



Biceps femoris inserts posterior to the LCL on the fibular head



Popliteofibular ligament inserts lateral to the LCL on the fibular head



Deep medial collateral ligament has both meniscofemoral and meniscotibial ligaments



L 1 C

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(OBQ09.260) A 25-year-old male injured his left knee in a motor cycle accident. During examination he is noted to have a positive reverse pivot shift test and a negative posterior drawer. What other examination finding is this patient expected to have?

QID: 3073

Positive anterior drawer test



Increased opening to valgus stress at 30 degrees of knee flexion



Positive apprehension sign with lateral patellar translation



A 10 degree increased external tibial rotation at 30 degrees of knee flexion



A 10 degree increased external tibial rotation at 90 degrees of knee flexion



L 2 C

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(OBQ09.90) Which of the following best describes the anatomic relationships of the lateral collateral ligament in the posterolateral corner?

QID: 2903

inserts directly anterior to popliteofibular ligament on the fibula and courses deep to popliteus



inserts anterolaterally to popliteofibular ligament on the fibula and courses superfical to popliteus



inserts posteromedially to popliteofibular ligament on the fibula and courses deep to popliteus



inserts directly posterior to popliteofibular ligament on the fibula and courses superficial to popliteus



inserts posterior and distal to biceps femoris tendon on the fibula and courses superficial to popliteus



L 1 C

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(OBQ07.123) A soccer player sustains a knee injury. He is noted to have a significant increase in tibial passive external rotation both at 30 and 90 degrees. Which of the following structures is least likely to be injured?

QID: 784

Fibular collateral ligament tear



Popliteus tendon tear



Posterior cruciate ligament tear



Arcuate ligament tear



Posterior oblique ligament tear



L 2 D

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(OBQ05.9) The pathologic motion of the lateral tibial plateau moving posteriorly to the femoral condyle on a rotational stress examination is best described by which of the following terms?

QID: 46

Anterior instability



Anteromedial rotatory instability



Anterolateral rotatory instability



Posteromedial rotatory instability



Posterolateral rotatory instability



L 1 D

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(OBQ04.148) A 34-year-old male presents with right knee pain, swelling, and symptoms of buckling 3 months after being involved in a motorcyle accident. He has a moderate effusion, positive Lachman, positive pivot shift, negative quadriceps active test, and medial sided knee pain with a positive Mcmurray test. Figure A demonstrates his leg external rotation at 30 degrees of flexion, however this deformity corrects with placing the knee at 90 degrees of flexion. Figure B shows a standing extremity alignment radiograph. Figure C shows a sagittal MRI image of the right knee. Appropriate surgical treatment includes each of the following EXCEPT:

QID: 1253

High tibial osteotomy (HTO)



ACL reconstruction



Arthroscopic medial partial menisectomy or repair



Posterolateral corner reconstruction



PCL reconstruction



L 2 C

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(OBQ04.251) A 20 year-old male football player sustains a knee injury after being hit below the knee while blocking. You suspect a posterolateral corner (PLC) injury, but are also concerned about a posterior cruciate ligament (PCL) tear. Which of the following positive exam findings is indicative of a combined PLC and PCL injury?

QID: 1356

Positive Dial test at 30 degrees of flexion



Valgus stress test opening at 0 and 30 degrees of flexion



Positive Posterior drawer test



Positive Pivot shift test



Positive Dial test at 30 and 90 degrees of flexion



L 1 C

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(OBQ04.105) Which of the following injury patterns is most appropriately managed with an immediate postoperative physical therapy regimen that includes no active flexion but does allow active extension from 90 to 0 degrees?

QID: 1210

Patellar tendon repair



Anterior cruciate ligament reconstruction



Anterior cruciate ligament reconstruction with medial collateral ligament repair



Anterior cruciate ligament reconstruction with posterolateral corner repair



Posterior cruciate ligament reconstruction with posterolateral corner repair



L 2 D

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Evidence (29)
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