LCL & PLC Injuries

Anatomy

Static Stabilizers

  • LCL
  • Popliteus tendon
  • Arcuate ligaments
  • Capsule

Dynamic Stabilizers

  • Biceps femoris
  • Popliteus muscle
  • ITB (Iliotibial band)
  • Lateral head of gastrocnemius

Popliteus Tendon

  • Intra-articular at the popliteal hiatus of the lateral meniscus.
  • Important stabilizer of the lateral meniscus via popliteomeniscal ligaments.

Arcuate Complex

  • Y-shaped ligamentous complex attaching to the fibula head.

Layered Structure

Layer Contents
Superficial Biceps Femoris, ITB, Common Peroneal Nerve
Middle Patellofemoral Ligament, Patella Retinaculum
Deep Superficial Lateral Collateral Ligament, Fabellofibular Ligament, Lateral Geniculate Artery
Deep Deep Popliteus Tendon, Arcuate Ligament, Coronary Ligament, Popliteofibular Ligament, Lateral Capsule

Capsule

  • Gives rise to meniscotibial and meniscofemoral ligaments.
  • Meniscotibial ligaments are associated with Segond fracture.
  • Meniscofemoral ligaments include Humphrey’s and Wrisberg’s ligaments.

LCL (Lateral Collateral Ligament)

  • Shape: Tubular.
  • Origin: Lateral epicondyle of femur to fibula head.
  • Blood Supply: Superolateral and inferolateral geniculates.
  • Biomechanics:
    • Primary restraint to varus at 5° and 25° knee flexion.
    • Primary restraint to external rotation (ER).
    • Popliteus restricts posterior tibial translation, external rotation, and varus.

Injury Mechanism and Symptoms

  • Varus and anterior-posterior (AP) stress to the knee, especially in extension.
  • Instability with knee extended.
  • Symptoms: Lateral pain, difficulty with stairs, unable to pivot on the knee.

Examination

Varus Instability

  • At 30° flexion: Indicates isolated LCL injury.
  • At 0° and 30° flexion: Suggests LCL and PCL or ACL involvement.

Dial Test

  • Test for PLC injury.
  • At 30° and 90° flexion: Positive if external rotation (ER) >10°.
    • Positive at 30° only indicates PLC.
    • Positive at both 30° and 90° indicates PCL involvement as well.

Reverse Pivot Shift

  • Extend the knee from a flexed position in external rotation (ER).
  • Feel for knee relocation.

External Recurvatum Test

  • Lift legs by big toes.
  • Look for ER and sag of tibia.

Posterolateral Drawer Test

  • At 30° and 90° flexion:
    • 30°: Positive indicates PLC.
    • 90°: Positive indicates PCL.

Classification of PLC Injury

  • Grade 1: Minimal damage, varus opening of the joint line.
  • Grade 2: Partial damage, <10mm opening.
  • Grade 3: Complete disruption, >10mm opening.

Management

Non-Operative Management

  • For grade 1 and 2 injuries.
  • ROM and quadriceps exercises with proprioceptive training.

Operative Management

  • Avulsed LCL.
  • Isolated unstable symptomatic grade 3 PLC (involving LCL and other PLC structures).
  • Combined injuries with PCL or ACL (more common).

Surgical Principles

  • Best results for PLC and LCL injuries with acute repair within 2-3 weeks.
  • After 2-3 weeks, scar tissue makes primary repair outcomes worse.
  • Acute setting: Use suture anchors for repair; direct repair can be done open.
  • Arthroscopy is used to screen for and treat intra-articular injuries.

Chronic PLC and LCL Instability

  • Use synthetic grafts (LARS) for LCL via drill holes.
  • Anatomic repair with Y-shaped Achilles allograft.
  • Often in combination with PCL or ACL reconstruction.
  • Concurrent treatment for PCL and ACL.
  • If patient has a pre-existing varus deformity, consider high tibial osteotomy (HTO) to correct the axis.
  • Common peroneal nerve should be identified below the biceps femoris at the fibula head and traced proximally.
  • Consider extension splinting post-op for 4 weeks to prevent external rotation of the tibia.
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