Meniscal Root Tears: The Silent Joint Killer

Meniscal root tears are a specific subset of meniscal injuries that, if missed, can have catastrophic consequences for the knee joint. Unlike a simple body tear, a root tear completely disrupts the meniscus's ability to distribute load, leading to rapid compartmental arthritis.

Visual Element: SVG Illustration of the "Ghost Sign" on MRI.

Anatomy and Biomechanics

The meniscal roots anchor the meniscus to the tibial plateau. This attachment is crucial for converting axial compression forces into "hoop stresses."

• Hoop Stress: When the knee is loaded, the wedge-shaped meniscus tries to extrude. The roots hold it in place, allowing the fibers to stretch and absorb the energy.
• Functional Meniscectomy: A tear of the posterior root (especially the medial meniscus) breaks this hoop. Biomechanically, the contact pressures in the compartment increase to levels seen in a total meniscectomy.

Visual Element: Biomechanical diagram showing hoop stress loss in root tears.

Clinical Presentation and Imaging

These tears often occur in middle-aged patients with a history of a "pop" during deep flexion (e.g., squatting).

• History: Pain is often posterior and worse with deep flexion. Mechanical symptoms like locking are less common than in bucket-handle tears.
• MRI Findings: The "Ghost Sign" on sagittal views (absence of the posterior horn triangle) and meniscal extrusion (>3mm) on coronal views are hallmark signs.

Management: Repair vs Resection

Historically, these were often treated with partial meniscectomy. However, recognizing their biomechanical importance has shifted the paradigm to repair.

• Transtibial Pull-out Repair: The gold standard technique. Sutures are passed through the root and pulled down a tunnel drilled in the tibia, re-anchoring the meniscus to its footprint.
• Outcomes: Successful repair can restore hoop tension and slow the progression of osteoarthritis. However, it requires a strict rehabilitation protocol (non-weight bearing) to protect the healing root.

Conclusion

High index of suspicion is key. Recognizing a root tear on MRI is the difference between offering a joint-preserving repair and watching a patient progress rapidly to a total knee replacement.