Meniscal Injuries

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Anatomy & Function - Knee's Cushions

  • Fibrocartilage discs: Medial (C-shaped), Lateral (O-shaped); between femur & tibia.
  • Composition: Primarily Type I collagen.
  • Blood Supply Zones (peripheral to central):
    • Red-Red (outer 1/3): Vascular, good healing.
    • Red-White (middle 1/3): Transitional.
    • White-White (inner 1/3): Avascular, poor healing.
  • Functions: Shock absorption, load transmission, ↑ joint stability & congruity, lubrication, proprioception.
  • Medial: Less mobile, attached to MCL (📌 "C" shape, Commoner injuries).
  • Lateral: More mobile. Knee Meniscus Anatomy and Blood Supply Zones

⭐ The peripheral vascular "red zone" (outer 10-30%) has healing potential, unlike the avascular "white zone" which relies on synovial fluid for nutrition.

Injury & Tears - Snap, Crackle, Pop!

  • Mechanism: Twisting on flexed, weight-bearing knee; often valgus force. Associated: ACL/MCL (📌 O'Donoghue's Triad: ACL + MCL + Medial Meniscus).
  • Symptoms: "Pop/snap", pain (may be delayed), effusion, locking, catching, giving way. Key: Joint line tenderness.
  • Tear Patterns:
    • Longitudinal/Vertical: Can become bucket-handle.
    • Radial: Disrupts circumferential fibers.
    • Horizontal/Cleavage: Often degenerative.
    • Oblique/Flap.
    • Complex.
  • Vascular Zones (Healing): Red-Red (peripheral, good), Red-White, White-White (central, poor). Meniscus vascular zones

⭐ A bucket-handle tear, a displaced vertical tear, is a common cause of true knee locking, often requiring urgent management to unlock the knee or repair the tear if possible based on tear characteristics and patient factors.

Clinical Features - Clicking & Locking

  • Clicking:
    • Audible/palpable snap or click with knee movement.
    • Often painful; indicates catching of torn meniscal fragment.
  • Locking:
    • Knee "stuck"; true inability to fully extend.
    • Caused by displaced fragment (e.g., bucket-handle tear) blocking motion.
    • Patient may "wiggle" or manipulate knee to unlock.
    • Differentiate from pseudo-locking (pain, hamstring spasm). Meniscal Tears and Knee Ligaments Diagram

    ⭐ True mechanical locking (inability to fully extend knee) strongly suggests a displaced bucket-handle tear, often of the medial meniscus.

Diagnosis & Imaging - MRI's Magic Eye

  • MRI: Gold standard. Accuracy >90%.
    • Details tear: type, location, extent.
    • MRI Grading (Stoller):
      • Grade 0: Normal.
      • Grade 1: Intrasubstance signal, no surface contact.
      • Grade 2: Linear signal, no surface contact.
      • Grade 3: Signal contacts articular surface (tear).
  • Key Signs: Double PCL, absent bow tie, flipped meniscus. MRI Sagittal Views of Meniscal Tears

⭐ Grade 3 signal (articular surface contact) on MRI confirms a meniscal tear.

Management - Repair or Remove?

Goal: Preserve meniscal tissue. Decision based on tear (type, location, stability), patient factors.

  • Conservative: Small (<1 cm), stable, peripheral, asymptomatic, or degenerative tears in low-demand patients.
  • Surgical Indications: Symptomatic, mechanical symptoms (locking), failed conservative, large tears.

Repair Criteria:

  • 📍 Location: Red-Red zone (vascular) > Red-White.
  • 📏 Size/Pattern: >1 cm, longitudinal, vertical.
  • 🏃 Patient: Young, active; ACL recon.

Meniscectomy:

  • Partial: Remove unstable fragment. Preferred.
  • Total: Irreparable, complex. ↑ OA risk.

⭐ Meniscal repair in the "red-red" zone (outer third) has the highest success rate due to good vascular supply.

High‑Yield Points - ⚡ Biggest Takeaways

  • Medial meniscus is injured more often than lateral.
  • Common mechanism: Twisting force on a partially flexed knee.
  • Classic signs: Joint line tenderness, locking, clicking, delayed effusion.
  • Provocative tests: McMurray, Apley's grind, and Thessaly test.
  • MRI confirms diagnosis and tear pattern.
  • "Red zone" (peripheral) tears heal better than "white zone" (central) tears.
  • Management: Conservative or arthroscopic surgery (repair/meniscectomy).

Practice Questions: Meniscal Injuries

Test your understanding with these related questions

Meniscal tears usually result from which of the following circumstances?

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Flashcards: Meniscal Injuries

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The _____ test is performed with the knee at a 90 degree angle to test for PCL injury.

TAP TO REVEAL ANSWER

The _____ test is performed with the knee at a 90 degree angle to test for PCL injury.

posterior drawer

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