Meniscus Tear on MRI

What You'll See on Your MRI

Before understanding what a meniscus tear looks like on an MRI, let's review some important context about this common knee injury.

Think of your menisci as two C-shaped pieces of cartilage in your knee that act as shock absorbers between your thigh bone (femur) and shin bone (tibia). The medial meniscus is on the inner side of your knee, and the lateral meniscus is on the outer side. When a meniscus tears, it can cause pain, catching, and locking of the knee.

Here are the key statistics about MRI accuracy for meniscus tears:

Understanding Meniscus Tears

The menisci are fibrocartilage structures that:

• Distribute weight across the knee joint
• Provide shock absorption
• Improve joint stability
• Lubricate the joint surface
• Limit extreme flexion/extension

Blood Supply and Healing:

• Red zone (outer 10-30%): Good blood supply, tears can heal with repair
• White zone (inner 70-90%): Poor blood supply, tears rarely heal, often require partial removal

Types of Meniscus Tears:

1. Longitudinal tear - Along the circumference of the meniscus
2. Bucket-handle tear - Displaced longitudinal tear fragment that flips into the intercondylar notch, causing locking
3. Radial tear - Extends from the inner margin toward the periphery
4. Horizontal tear - Splits the meniscus into upper and lower layers
5. Complex tear - Combination of multiple tear patterns
6. Flap tear - A portion of the meniscus is flipped upward
7. Root tear - Detachment of the meniscus from its attachment site

Symptoms:

• Joint line pain (medial or lateral)
• Catching or locking sensation
• Swelling (often delayed 24-48 hours)
• Inability to fully straighten the knee
• Knee giving way
• Pain with squatting or twisting

How It Appears on Imaging

Let's compare what a normal meniscus looks like versus what a torn meniscus looks like on an MRI:

Key Findings Pattern

When interpreting an MRI for meniscus tear, radiologists assess specific features:

When Your Doctor Orders This Test

Here's a typical clinical scenario where an MRI is ordered for suspected meniscus tear:

Your doctor might order an MRI for suspected meniscus tear if you have:

| Symptom | Why It Matters | |---------|----------------| | Joint line tenderness | Localized pain over medial or lateral joint line | | Positive McMurray test | Pain or click with knee rotation and extension | | Locking or catching | Mechanical symptom suggesting displaced fragment | | Inability to fully extend | Blocked by torn meniscus fragment | | Effusion (swelling) | Indicates joint irritation from meniscus tear |

What Else Could It Be?

Not every knee pain is a meniscus tear. Here's what else could be causing similar symptoms:

How Accurate Is This Test?

The evidence for MRI in meniscus tear diagnosis shows excellent performance:

What Happens Next?

If your MRI confirms a meniscus tear, here's what to expect:

Prognosis and Treatment Outcomes

Repair vs Meniscectomy:

• Meniscus repair: Preserves meniscus, prevents arthritis. Success rate 70-90% in vascular zone. Longer recovery (3-4 months). Best for young patients with traumatic tears.
• Partial meniscectomy: Removes torn portion only. Faster recovery (2-4 weeks). Removes shock absorber, increasing arthritis risk.

Long-Term Outcomes:

• After partial meniscectomy: 50-70% develop knee arthritis within 10-15 years
• After successful repair: Lower arthritis risk but still elevated compared to normal knee
• Return to sports: Most athletes return after 4-8 weeks depending on treatment

Factors Influencing Outcomes:

• Better: Repair in vascular zone, young patient, acute tear, stable knee
• Worse: Complex or degenerative tears, root tears, associated cartilage damage, prior meniscectomy

Frequently Asked Questions

Will a meniscus tear heal on its own?

Tears in the vascular outer third (red zone) can heal with repair or sometimes even with rest. Tears in the inner two-thirds (white zone) have poor blood supply and rarely heal without surgical intervention.

Do I need surgery for a meniscus tear?

Not necessarily. Many degenerative tears improve with physical therapy and activity modification. Surgery is more likely recommended for: young active patients, traumatic tears, repairable tears, and mechanical symptoms (locking) that don't improve with conservative care.

Can I walk with a torn meniscus?

Yes, you can walk with a meniscus tear. However, if the knee is locked or you have severe pain, you should avoid walking on it and seek evaluation. Most patients can continue activities as tolerated.

What happens if a torn meniscus is left untreated?

Degenerative tears may remain stable or slowly worsen. Untreated tears in young active patients can lead to: meniscus displacement causing locking, cartilage damage from the torn fragment, and accelerated osteoarthritis from loss of meniscal function.

Will I regain full function after meniscus surgery?

Most patients return to normal activities. However, there's an increased risk of developing arthritis in the future. Preserving as much meniscus as possible (repair over meniscectomy) improves long-term outcomes.

References

Medical Disclaimer: This information is for educational purposes. Always discuss your imaging results with your orthopedic surgeon or healthcare provider for personalized medical advice.