knee ligaments.jpg cross-section.jpg supply to the knee.jpg structures of the knee.jpg stress radiographs.jpg
  • Injury to the Lateral Collateral Ligament (LCL)
    • also referred to as fibular collateral ligament
  • Epidemiology
    • demographics
      • incidence
        • isolated injury extremely rare
        • 7-16% of all knee ligament injuries when combined with lateral ligamentous complex injuries
          • particularly posterolateral corner (PLC) injury  
  • Mechanism
    • traumatic
      • most frequently result from MVAs and athletic injuries
        • direct blow or force to weightbearing knee 
        • excessive varus stress, external tibial rotation, and/or hyperextension
  • LCL characteristics
    • tubular, cordlike structure
    • dimensions
      • 3-4 mm diameter
      • 66 mm length
    • origin
      • lateral femoral epicondyle
      • posterior and proximal to insertion of popliteus  
    • insertion
      • anterolateral fibula head
      • most anterior structure on proximal fibula 
        • order of insertion from anterior to posterior 
          • LCL → popliteofibular ligament → biceps femoris
  • Blood supply
    • superolateral and inferolateral geniculate arteries 
  • Biomechanics
    • function
      • primary restraint to varus stress at 5° and 25° of knee flexion
        • provides 55% of restraint at 5°
        • provides 69% of restraint at 25°
      • secondary restraint to posterolateral rotation with <50° flexion
      • resists varus in full extension along with ACL and PCL
    • located behind the axis of knee rotation
      • tight in extension and lax in flexion
    • tensile strength: 750 N (valgus)

Lateral Structures of Knee 
Layer I  Iliotibial tract, biceps, fascia 
Common peroneal nerve lies between layers I and II
Layer 2 Patellar retinaculum, patellofemoral ligament  
Layer 3 SuperficialLCL, fabellofibular ligament 
Inferior lateral geniculate artery runs between deep and superficial layers
Deep: arcuate ligament, coronary ligament, popliteus tendonpopliteofibular ligament, capsule 

  • LCL/PLC injury
    • based on quantification of lateral joint opening as compared with the normal contralateral knee with varus stress
      • grade 1+: 0-5 mm lateral opening
      • grade 2+: 6-10 mm lateral opening
      • grade 3+: >10 mm lateral opening without an endpoint
    • sprains classified according to amount of ligamentous disruption
      • grade I: minimal
      • grade II: partial
      • grade III: complete
  • Symptoms
    • instability near full knee extension
    • difficulty ascending and descending stairs
    • difficulty with cutting or pivoting activities
    • lateral joint line pain and swelling
  • Physical exam
    • inspection and palpation
      • ecchymosis and lateral joint line tenderness
    • ROM & stability
      • varus stress test post post
        • varus instability (lateral opening) at 30° flexion only - isolated LCL injury  
        • varus instability at 0° and 30° flexion - combined LCL and/or ACL/PCL injuries
      • dial test post
        • varus instability and increased tibial external rotation at 30° flexion - combined LCL and posterolateral corner injuries 
    • gait assessment post
      • hyperextension or varus (lateral) thrust gait
    • neurovascular exam
      • common peroneal nerve injuries may occur with LCL/PLC injury
  • Radiographs
    • recommended views
      • AP, lateral, and varus stress radiographs 
  • MRI
    • imaging modality of choice
    • provides information about severity (complete vs. partial rupture) and location (avulsion vs. midsubstance tear) 
  • Nonoperative
    • limited immobilization, progressive ROM, and functional rehabilitation
      • indications
        • isolated grade I or II LCL injury (no instability at 0°)
      • outcomes
        • return to sport expected in 6-8 weeks
        • progressive varus/hyperextension laxity can occur with unrecognized associated injuries to the PLC
  • Operative
    • LCL repair/reconstruction +/- PLC/ACL/PCL reconstruction
      • indications
        • grade III LCL injury
        • rotatory instability involving LCL/PLC
        • posterolateral instability (LCL/PLC) at 0° (ACL/PCL rupture)
      • outcomes
        • more favorable outcomes with surgery when injuries are acute
Surgical Techniques
  • Acute LCL repair
    • approach
      • lateral approach to the knee 
        • uses the interval between iliotibial band (superior gluteal nerve) and biceps femoris (sciatic nerve)
        • incise the fascia between ITB and biceps to expose the LCL insertion on the fibular head
        • develop a second interval proximally within ITB to identify the lateral femoral epicondyle
    • techniques
      • suture anchors for repair of avulsed ligament
      • direct suture repair for midsubstance ruptures
      • repair torn or avulsed ligament within 2 weeks of injury (reconstruct if native tissue is irreparable)
  • LCL +/- PLC reconstruction
    • approach
      • lateral approach to the knee
        • between ITB and biceps femoris as detailed above
    • techniques
      • single-stranded graft (bone-patellar tendon-bone) for isolated LCL injuries
      • fibular-based reconstruction (Larson technique) for LCL and popliteofibular ligament reconstruction
        • hamstring graft passed through bone tunnel in fibular head
        • limbs crossed to create figure-of-eight which is then fixed to lateral femur
      • transtibial double-bundle reconstruction of LCL and popliteofibular ligament
        • split Achilles tendon is fixed to the isometric point of the femoral epicondyle
        • one limb is fixed to the fibular head with a bone tunnel and transosseous sutures to reconstruct the LCL
        • second limb is brought through the posterior tibia to reconstruct the popliteofibular ligament
      • anatomic reconstruction of multiple injured structures (LCL, popliteus tendon, and popliteofibular ligament) using bifid graft (split Achilles tendon)
  • Persistent varus or hyperextension laxity
  • Peroneal nerve injury
  • Stiffness
  • Hardware irritation

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Questions (2)

(OBQ11.154) A 27-year-old recreational soccer player injures his knee after colliding with an opposing player during a game. On physical exam, his Lachman is graded as 1A. He has laxity to varus stress with the knee flexed to 30 degrees. Dial test of the tibia shows increased external rotation at 30 degrees, but not at 90 degrees in comparison to the contralateral leg. Which of the following structure(s) are torn? Review Topic


Anterior cruciate ligament (ACL)




Lateral collateral ligament (LCL)




Anterior cruciate ligament (ACL) and lateral collateral ligament (LCL)




Lateral collateral ligament (LCL) and posterolateral corner (PLC)




Posterior cruciate ligament (PCL) and posterolateral corner (PLC)



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The individual in the above scenario likely has torn his lateral collateral ligament (LCL) and posterolateral corner (PLC). The LCL is part of the posterolateral corner, but can be injured in isolation or along with the rest of the posterolateral corner. An isolated LCL tear would be tested by flexing the knee at 30 degrees and applying varus stress. The posterolateral corner can be tested by the dial test, which is done by externally rotating the affected tibia. A PLC injury shows increased external rotation at 30 degrees, while a combined PLC/PCL injury would show increased external rotation at 30 and 90 degrees.

Lubowitz et al review the history and physical examination used in determining ligamentous instability of the knee joint. Ultimately, information must be obtained from multiple tests and imaging to reach the final diagnosis.

Chen et al review isolated posterolateral rotatory instability (PLRI)of the knee. Although these injuries are rare, they do result in significant instability in the knee. In the article, they discuss physical exam maneuvers to distinguish PLC vs PCL injuries. They describe that posterolateral subluxation of the lateral tibial plateau only at 30 degrees is indicative of isolated PLC injury vs subluxation at both 30 and 90 degrees is indicative of combined PLRI and PCL injury.

Attached is a video showing physical exam maneuvers including the dial test which test the posterolateral corner.

Incorrect resonses:
1: Isolated ACL injury would have a positive Lachman's test with increased anterior knee translation at 30 degrees of knee flexion. In the given scenario, Grade 1A indicates less than 5mm of translation and a firm endpoint indicating that the ACL is intact.
2: Isolated LCL injury would have increased laxity to varus force at 30 degrees of knee flexion, but would not have a positive dial test.
3: Would have both ACL and LCL findings as above.
5: Would have increased external rotation of tibia at both 30 and 90 degrees of knee flexion.


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(OBQ07.200) In relation to the femoral insertion of the popliteus, the femoral attachment of the lateral collateral ligament is Review Topic


posterior and proximal




posterior and distal




anterior and proximal




anterior and distal




directly superficial



Select Answer to see Preferred Response


LaPrade in a cadaveric study of 10 knees found that the lateral (or fibular) collateral ligament (LCL) had an average femoral attachment 1.4mm proximal and 3.1mm posterior to the lateral epicondyle. The popliteus has a broad-based femoral attachment at the most proximal and anterior fifth of the popliteal sulcus and always attaches anterior to the fibular collateral ligament. Thus, the LCL's femoral attachment is posterior and proximal compared to the popliteus femoral insertion with the average distance between their femoral attachments being 18.5 mm. See illustration from article (FCL=LCL, popliteus=PLT)


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