Meniscal Tears and Repair

Anatomy & Function

• Load distribution — transmitting ~50–70% of compressive forces across the knee compartment
• Shock absorption
• Joint stability and proprioception

Epidemiology

• Meniscal tear is the most common knee injury requiring surgery
• The medial meniscus is torn ~3× more often than the lateral
• However, lateral meniscus tears occur more commonly with acute ACL injuries
• Traumatic tears predominate in young, athletic patients; degenerative tears occur insidiously in older patients

Vascular Zones (Key to Healing Potential)

Classification of Tear Patterns

Types of meniscal tears (Miller's Review of Orthopaedics)

Degenerative (left) vs. traumatic (right) meniscal tear patterns (Textbook of Family Medicine)

By Orientation

Meniscal Root Tears

• Defined as a radial tear or avulsion of the meniscal root from the tibial plateau
• Completely disrupts the circumferential (hoop) fibers, abolishing hoop stress
• Biomechanically equivalent to total meniscectomy
• Lateral root tears → associated with ACL tears
• Medial root tears → associated with chondral injuries
• Acute root tears should be repaired whenever possible

Clinical Presentation

• Joint line tenderness (medial or lateral)
• Intermittent locking, clicking, or catching
• Giving way sensation
• Effusion (often delayed)
• Recurrent swelling with activity

Physical Examination

• McMurray test: Knee hyperflexed, varus/valgus stress applied while internally/externally rotating the tibia as the knee is brought to extension. A palpable click + pain = positive (highly indicative of tear)
• Apley grind test, Thessaly test also used

Imaging

Coronal MRI of the knee showing a medial meniscus tear (Gray's Anatomy for Students)

• Plain radiographs and CT cannot diagnose meniscal tears
• Arthroscopy remains the gold standard for diagnosis and is simultaneously therapeutic

Management

Conservative (Non-Operative)

• Degenerative tears without mechanical symptoms
• Partial-thickness tears, tears <5–10 mm, or those that cannot be displaced >1–2 mm
• Initial management for all: NSAIDs, activity modification, physiotherapy, ice, corticosteroid injections

In the absence of intermittent swelling, catching, and locking, meniscal tears—particularly degenerative tears—may be treated conservatively. — Miller's Review of Orthopaedics

Surgical Options

1. Partial Meniscectomy

• For tears not amenable to repair (complex, degenerative, central/radial tears)
• Goal: resect minimal normal tissue
• Recovery: weight-bearing as tolerated, return to activities ~3–4 weeks
• Downside: increases peak stresses in the affected compartment → long-term OA risk

2. Meniscal Repair

• Tear length 1–4 cm
• Vertical tear orientation
• Red-red zone (vascularized)
• Meniscal root tear
• Patient < 40 years old
• Concomitant ACL reconstruction (extends indications; improves results)

Surgical Techniques

Meniscal repair techniques: outside-in, inside-out (gold standard), all-inside (Miller's Review of Orthopaedics)

• Medial repairs → protect saphenous nerve branches (anterior to semitendinosus/gracilis, posterior to sartorius)
• Lateral repairs → protect peroneal nerve (posterior to biceps femoris)

Outcomes of Repair

Special Considerations

Meniscal Cysts

• Primarily associated with horizontal cleavage tears of the lateral meniscus
• Treatment: arthroscopic partial meniscectomy or repair + decompression through the tear
• En bloc excision is no longer favored

Baker (Popliteal) Cysts

• Commonly related to meniscal disorders
• Located between the semimembranosus and medial head of gastrocnemius
• Usually resolve with treatment of the underlying meniscal pathology

Discoid Meniscus

• Congenital variant; lateral meniscus more commonly affected
• May cause "snapping knee syndrome" in children

Recent Evidence

Meniscal Tears on MRI — A Complete Visual Guide

MRI Basics: What You're Looking For

1. Increased signal intensity within the meniscus extends to the articular surface (superior or inferior margin)
2. Distortion of the normal meniscal morphology
3. Discontinuity of the fibrocartilage

Internal "globular" or "linear" high signal that does not reach the surface = intrasubstance degeneration (not a true tear, no surgical significance)

Overview of Tear Types — Anatomy to MRI Correlation

Overview: tear patterns correlated with imaging and arthroscopy (PMC)

1. Horizontal (Cleavage) Tear

• Linear high signal running horizontally through the meniscal substance, extending to the inferior articular surface (or both surfaces)
• Most common in the posterior horn of the medial meniscus
• May be asymptomatic; joint fluid can escape → parameniscal cyst

Horizontal tear — posterior horn medial meniscus (Grainger & Allison's Diagnostic Radiology)

2. Longitudinal (Vertical) Tear

• Vertical cleft within the peripheral substance of the meniscus on coronal views
• High signal intensity confined to the peripheral third
• Healing potential is better here due to vascular supply

Longitudinal tear — peripheral medial meniscus (Grainger & Allison's Diagnostic Radiology)

3. Bucket-Handle Tear

Double PCL Sign (Sagittal)

Bucket-handle medial meniscus tear — Double PCL sign (Miller's Review of Orthopaedics)

Fragment-in-Notch Sign (Coronal)

Bucket-handle tear — fragment-in-notch sign, coronal view (Grainger & Allison's Diagnostic Radiology)

Bucket-handle tear — "fragment-in-notch" sign (PMC)

Double Anterior Horn Sign (Sagittal)

4. Radial Tear

• Sagittal: high-signal "blunting" or truncation of the free edge — the normal pointed triangular shape is lost
• Coronal/axial: focal gap in the meniscal substance
• Complete radial tear → "Ghost Meniscus" sign: the section passes through the gap, showing no meniscal tissue where it should be

Radial tear — sagittal PD fat-sat (Grainger & Allison's Diagnostic Radiology)

Ghost Meniscus sign — complete radial tear (Grainger & Allison's Diagnostic Radiology)

5. Meniscal Root Tear

• Sagittal: "Ghost sign" — absent posterior horn signal where root should anchor
• Coronal + axial: focal high-signal gap at root attachment
• Key secondary finding: meniscal extrusion >3 mm beyond the tibial margin (loss of hoop stress causes the meniscus to be extruded radially)
• Medial root tears: often associated with subchondral marrow edema and cartilage loss

Medial meniscal posterior root tear with measurable meniscal extrusion (PMC)

Meniscal root avulsion with bony fleck (Miller's Review of Orthopaedics)

6. Complex / Degenerative Tear

• Diffuse irregular high signal involving multiple planes
• Distorted meniscal morphology
• Often involves the posterior horn of the medial meniscus
• Associated with articular cartilage loss and subchondral edema

Summary Table