Updated: 7/6/2020

LCL Injury of the Knee

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  • Overview
    • Injury to the Lateral Collateral Ligament (LCL) typically occurs due to varus force to the knee
      • also referred to as Fibular Collateral Ligament (FCL)
      • treatment depends on degree of injury to the ligament as well injuries to surrounding structures
  • Epidemiology
    • incidence
      • isolated injury extremely rare (< 2% knee injuries)
      • 7-16% of all knee ligament injuries when combined with concurrent injuries
        • particularly posterolateral corner (PLC) injury  
    • demographics
      • isolated LCL injuries are most commonly seen in gymnasts and tennis players
  • Pathophysiology
    • traumatic
      • direct blow or force to the medial side of the knee
      • excessive varus stress, external tibial rotation, and/or hyperextension
  • Associated conditions
    • injuries to other components of PLC
    • ACL injuries
    • PCL injuries
  • Prognosis
    • LCL healing can be unreliable and depends on degree of injury
      • studies show that the LCL does not heal as well as the MCL
  • LCL 
    • characteristics
      • tubular, cordlike structure
      • dimensions
        • 2-3 mm thick
        • 4-5 mm wide
        • 66 mm length
    • origin
      • posterior (3.1 mm) and proximal (1.4 mm) to lateral epicondyle 
      • posterior and proximal to origin of popliteus  
        • popliteus origin is 18.5 mm from LCL origin
    • insertion
      • anterolateral fibula head
        • covers 38% of the fibular width
      • most anterior structure on proximal fibula 
        • order of insertion from anterior to posterior 
          • LCL → popliteofibular ligament → biceps femoris
    • Blood supply
      • anterior tibial recurrent arteries and inferolateral geniculate arteries 
  • Biomechanics
    • function
      • primary restraint to varus stress at 5° and 30° of knee flexion
        • provides 55% of restraint at 5°
        • provides 69% of restraint at 30°
      • 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)
LCL tear classification 
(based on lateral joint opening compared to contralateral side)
Grade 1  0-5 mm lateral joint opening
Grade 2  6-10 mm lateral joint opening
Grade 3  > 10 mm lateral joint opening without a firm endpoint
LCL tear MRI classification 
Grade 1 Subcutaneous fluid surrounding the midsubstance of the ligament at one or both insertions
Grade 2 Partial tearing of ligament fibers at either the midsubstance or one of the insertions 
Grade 3 Complete tearing of ligament fibers at either the midsubstance or one of the insertions


  • Symptoms
    • common 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
      • ecchymosis and lateral joint soft tissue swelling
    • palpation
      • tenderness over LCL insertion
        • entire length of ligament can be palpated by placing patient in figure-of-4 position 
          • intact ligament will be a palpable cordlike structure
    • motion post
      • hyperextension or varus (lateral) thrust gait
    • neurovascular exam
      • common peroneal nerve injuries may occur with LCL/PLC injury
    • provocative tests
      • varus stress test post post
        • varus instability at 30° flexion only - isolated LCL injury  
        • varus instability at 0° and 30° flexion - combined LCL +/- ACL/PCL injuries
      • dial test post
        • increased tibial external rotation (> 10° compared to contralateral side) at 30° knee flexion 
          • combined LCL and posterolateral corner injuries 
  • Radiographs
    • recommended views
      • weightbearing AP, lateral, and varus stress radiographs 
    • findings
      • may show asymmetric lateral joint line widening
  • MRI
    • indications
      • imaging modality of choice to grade severity and location of LCL injury
    • findings
      • most tears are noted off of fibular insertion  
      • medial compartment bony contusions on T2-weighted images
        • correlate with LCL/PLC injury due to a hyperextension-varus mechanism
    • sensitivity
      • 95% sensitivity
      • much higher senstivity than exam under anesthesia (58%) since lesions are often difficult to isolate on examination alone
  • 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
    • isolated LCL repair
      • indications
        • isolated acute (< 2 weeks) grade III LCL injury with avulsed ligament from anatomic attachment site (i.e fibula)
      • outcomes
        • some studies have shown failure rates as high as 40% with repair
    • isolated LCL reconstruction
      • indications
        • subacute/chronic (> 2 weeks) grade III LCL injury with persistent varus instability
        • complete mid-substance acute grade III LCL injury with persistent varus instability
      • outcomes
        • studies shown consistently better outcomes compared to LCL repair 
        • 6% failure rate at 3 year followup
        • best results noted with anatomic reconstruction using a semitendinosus autograft
    • LCL + PLC reconstruction
      • indications
        • rotatory instability involving LCL/PLC
        • posterolateral instability (LCL/PLC) 
      • outcomes
        • more favorable outcomes when surgeries are done acutely after injury
  • limited immobilization, progressive ROM, and functional rehabilitation
    • progressive ROM of the knee with subsequent emphasis on quadriceps and hamstring strenghthening
    • early studies showed treatment with 6 weeks of casting effective at healing
      • led to signficant knee stiffness

  • Isolated 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, if needed
        • develop a second interval proximally within ITB to identify the insertion on lateral femoral epicondyle, if needed
        • neurolysis of peroneal nerve should be performed
    • techniques
      • traction suture should be placed in ligament to determine if repair is possible (with knee in extension)
      • suture anchors for repair of avulsed ligament to femur or fibula
  • Isolated LCL reconstruction
    • approach 
      • lateral approach to knee as detailed above
    • technique 
      • commonly used grafts
        • semitendinosus autograft, patellar tendon allograft, achilles tendon allograft
          • semitendinosus autograft is preferred graft for LCL reconstruction
            • since LCL is ~70 mm, semitendinosis provides a closer anatomical size as compared to other grafts 
              •  ~50 mm is size of patellar tendon autograft
            • semiteninosus stronger than gracilis and less chance of saphenous nerve irritation during harvest
      • anatomic reconstruction
        • fibular tunnel
          • drill from lateral aspect of fibula head towards the posteromedial asepct of fibular styloid, just distal to popliteofibular ligament
        • lateral femoral condyle tunnel
          • starting point just posterior to lateral epidconyle (~ 3 mm) exiting anteromedially
      • complications
        • donor site morbidity 
          • semitendinosus and gracillus autograft
            • saphenous nerve neuropraxia
            • MCL injury
  • LCL + PLC reconstruction
    • approach
      • lateral approach to the knee as detailed above
    • techniques
      • 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
    • risk factors
      • type III injuries managed non-operativetly 
      • missed concomitant PCL or PLC injury
  • Peroneal nerve injury
    • incidence
      • occurs in up to 44% of multi-ligamentous injuries that involve the LCL/PLC
  • Stiffness
    • risk factors
      • prolonged immobilization following nonoperative management
  • Physeal arrest
    • risk factors
      • errant lateral condylar LCL fixation during reconstruction in skeletally immature patient

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(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? Tested Concept

QID: 3577

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)



L 2 C

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

QID: 861

posterior and proximal




posterior and distal




anterior and proximal




anterior and distal




directly superficial



L 3 C

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Evidence (14)
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