Meniscal Pathology

Introduction

• Presentation by David Rubin, adapted by Robin Smithuis.
• Provides interactive cases for knowledge testing.

Normal Meniscal Anatomy

Medial Meniscus

• Triangular horns, posterior horn larger than anterior.
• Abnormal shape signifies meniscal tear or partial meniscectomy.
• Posterior root is anterior to the posterior cruciate ligament (PCL).
• Anterior horn connects to lateral meniscus via transverse ligament.

Lateral Meniscus

• Posterior horn is higher than anterior.
• Both horns similar in size.
• High signal intensity might be due to magic angle effect.

Meniscal Tears

Criteria for Tears

• Abnormal meniscus shape.
• High signal intensity contacting surface on PD images indicates a tear.
• Misconception: Meniscus doesn’t need to be homogeneously low in signal.

Nomenclature of Meniscal Tears

• Longitudinal, Horizontal, and Radial Tears: Basic shapes.
• Displaced Tears:
  • Bucket-handle: Displaced longitudinal tear.
  • Flap tear: Displaced horizontal tear.
  • Parrot beak: Displaced radial tear.

Specific Tear Types

Longitudinal Tears

• Parallel to meniscus long axis, dividing it into inner and outer parts.
• Bucket-handle tear: Displaced longitudinal tear.
• Flipped meniscus: Posterior horn flips over the anterior horn.

Horizontal Tears

• Divide meniscus into a top and bottom part.
• May lead to the formation of a meniscal cyst.
• Criteria: Horizontal tear, fluid accumulation on T2, flat lining against meniscus.

Radial Tears

• Perpendicular to meniscus long axis, high energy tears.
• Triangle missing tip or disrupted bow tie indicates radial tear.

Meniscal Root Tear

• A radial tear located at the meniscal root.
• Absence of meniscus next to PCL on sagittal images is a sign.

Post-operative Meniscus

• Abnormal signal and shape aren't reliable for tears.
• Signal could indicate scar tissue or synovial fluid.
• Comparison with prior images essential for evaluation.
• MR-arthrography aids in distinguishing between healed and new tears.

References

• Rubin DA and colleagues' publications on MR imaging of knee injuries.

This lecture provides detailed insights into the normal anatomy and various pathologies associated with the meniscus, focusing on the criteria and identification of different tear types. Understanding these can aid in the accurate diagnosis and treatment planning for meniscal injuries.