Multi-Ligament Knee Injury

Overview

  • High-energy injury.
  • 3 or more ligaments involved is considered a knee dislocation.

Pathoanatomy

  • Both Cruciate ligaments are almost always torn.
  • Up to 30% risk of popliteal artery injury.
  • Up to 30% risk of peroneal nerve injury.

Associated Injuries

  • Extensor Mechanism.
  • Fractures to knee.
  • Systemic high-energy injuries.

Examination

Vascular Examination

  • Critical: Check pulses, Doppler, and Ankle-Brachial Pressure Index (ABPI).
  • ABPI:
    • <0.9 is suspicious.
    • <0.8 is abnormal.
    • Note: ABPI may be falsely high in chronic diabetics.
  • Repeat vascular exams periodically, as intimal tears can worsen over time, leading to false aneurysms.

Neurologic Exam

  • Common peroneal nerve is the most commonly injured (up to 30%).

Other Assessments

  • Compartment Syndrome.
  • Extensor Mechanism.
  • Assess for ligament instability (Lachman, Posterior Drawer, ER recurvatum, and Dial tests are useful acutely).

Imaging

  • X-rays: Fractures and knee reduction.
  • MRI: Soft tissue injuries and joint status.
  • Angiography: If there is any hint of vascular compromise (potentially routine in severe cases).

Classification of Knee Dislocations

  • KD1: Cruciates intact (rare without severe bony injury).
  • KD2: Cruciates torn, both collateral ligaments intact.
  • KD3M: Cruciates plus MCL torn.
  • KD3L: Cruciates plus LCL torn.
  • KD4: All 4 ligaments torn.
  • KD5: Fracture dislocation.
  • Note: Also describe as the direction of tibial translation (posterior is the most common).

Management

Non-Surgical

  • For elderly, very sick, or when the leg is unviable.

Surgical

  • Address limb-threatening problems first (vascular/compartment syndrome).
  • Timing:
    • Stabilize lateral or PLC injuries within 3 weeks.
  • How much to do?
    • More acute reconstruction allows earlier range of motion (ROM) and prevents fixed subluxation, though it may cause arthrofibrosis.
    • Collateral repair can be done first, with ACL and PCL addressed later.

Ex-Fix Application

  • Provides soft tissue rest in an anatomical position.
    • Disadvantages: Pin tracks may cause future issues, and stasis can lead to arthrofibrosis.
    • Preferred: Early ROM and weight-bearing when possible.

Injuries to the Medial Structures of the Knee

Anatomy

Superficial Medial Collateral Ligament (sMCL)

  • Origin: Adductor tubercle (just above the medial epicondyle of femur).
  • Insertions:
    • Semimembranosus rim.
    • Tibia.
  • Primary restraint to valgus force.

Deep Medial Collateral Ligament (dMCL)

  • Deep to the superficial ligament, continuous with the medial joint capsule.
  • Has 2 parts:
    • Meniscofemoral.
    • Meniscotibial.
  • Secondary restraint to valgus and especially external rotation.

Posterior Oblique Ligament (POL)

  • Fibrous extension of the semimembranosus tendon.
  • Blends with and reinforces the posteromedial joint capsule.
  • Restrains against valgus and internal rotation.

Injury Classification

  • Clinical Diagnosis relies on the patient’s ability to tolerate examination.
    • Otherwise, laxity may be underestimated.

Classification

  • Grade 1: Pain but no laxity at 20-30 degrees flexion.
  • Grade 2: Pain and mild laxity (MRI reveals partial tear of POL and sMCL).
  • Grade 3: Complete disruption of all structures with significant laxity.

Healing

  • sMCL has a rich blood supply and heals well.
  • Ligament strength improves with movement and loading.
  • Full immobilization during rehab is detrimental.

Clinical Diagnosis

History

  • Valgus force injury.
  • Difficulty with sports requiring turning and cutting movements.
  • Pain around the medial aspect of the knee.

Examination

  • Tenderness over medial structures.
  • Bruising/swelling.
  • Laxity testing in extension and 30 degrees flexion:
    • Stable in extension but not in flexion = POL intact.
  • End point presence: With complete tear, ACL is the only remaining valgus restraint.
  • Anteromedial draw test: Externally rotate the tibia while performing an anterior draw.
    • External rotation increases with complete MCL tears.

Radiographic Evaluation

  • X-rays: Avulsion fractures, comparative stress radiographs to demonstrate laxity.
  • MRI: Quantify if the deep part of the MCL is torn and assess for other injuries.
    • Bone bruising on the lateral tibial plateau can be noted.

Management

Non-Operative Treatment

  • Generally, grade 1 and 2 tears can be managed non-operatively with good results.
  • sMCL heals well due to its blood supply.
  • All grade 1 and 2 injuries should be treated non-operatively.

Grade 3 Injuries

  • Initially treated non-operatively.
  • May require repair if persistent instability is present.

Non-Operative Treatment Protocol

  • Functional rehab program with early weight-bearing and ROM.
  • Knee brace for protection against valgus and external rotation.

Operative Treatment

  • Goal: Restore anatomy of the superficial ligament, especially its two tibial attachments.
  • Options:
    • Direct repair with or without augmentation.
    • Reconstruction with autograft or allograft.
    • sMCL advancement to tighten medial structures.
    • Pes Anserinus transfer.

Pellegrini-Stieda Syndrome

  • Definition: Intraligamentous calcification resulting from a chronic MCL (Medial Collateral Ligament) tear, typically on the femoral side.

  • Symptoms:

    • May be painful due to the calcification or associated inflammation.
    • The heterotopic bone (abnormal bone formation) can sometimes contribute to discomfort.

  • Management:

    • Avoid operative treatment if possible.
    • If necessary, surgical excision of the calcified tissue may be considered in persistent or debilitating cases.
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