Meniscal Tears

Biomechanics

  • Load sharing function due to high conformity:
    • Increasing contact area decreases contact stress
  • Lateral meniscus bears more load than medial
  • Lateral meniscus is more mobile, hence less frequently injured
  • Together, the menisci:
    • Absorb 50% of load in extension
    • Absorb 90% at 90 degrees flexion
  • Contact stress increases in proportion to the amount of meniscus resected

Composition

  • 75% water
  • 1% dry weight proteoglycan
  • Type 1 collagen mainly (50% dry weight)
  • Collagen types 2, 3, 5, and 6 also identified

Blood Supply

  • From medial and lateral geniculate arteries via perivascular capillary plexus which infiltrates the periphery
  • 3 zones: Only the peripheral 1/3 is vascularized
    • At birth, the majority of the meniscus is vascular
    • By 10 years old, an avascular region develops

Injury

  • Rare in those <10 years old
  • Acute or chronic
  • Mechanism: Typically pivoting or deep flexion

Signs & Symptoms

  • Slow onset effusion
  • Recurrent effusions
  • Positive McMurray’s test (only accurate in 75%)
    • False positives due to other pathology
  • Catching, locking, sharp localized pain – mechanical symptoms

Imaging

  • Weight-bearing X-ray:
    • Rule out OCD (Osteochondritis Dissecans)
    • Screen for OA changes
    • Signs typical of a discoid meniscus:
      1. Squaring of lateral femoral condyle (LFC)
      2. Widened lateral joint space
      3. Hypoplasia of lateral tibial spine
      4. Cupping of lateral plateau
  • MRI:
    • High negative predictive value
    • Tear must exit onto the articular surface on two consecutive slices

Classification of Tears

  • By morphology, location (zone), and stability
    • Medial meniscus (MM) tears are more common
    • Lateral meniscus (LM) resection causes a higher increase in contact pressures
  • Complex tears: Multiple tear directions, don’t fit one pattern

Management

Best outcomes are seen in: - Younger patients - Stable knees (especially ACL intact) - Normal alignment - No evidence of arthritis

Tears Most Amenable to Non-Operative Management:

  • Any stable or asymptomatic tear
  • Small radial tears
  • Horizontal cleavage tears of <1 cm in length
  • Chronic tears associated with arthritis

Partial Meniscectomy

  • Best for central zone tears (white on white)
  • Horizontal cleavage, radial, oblique, and flap tears
  • Displaced bucket handle tears
  • Patients over 40
  • Delayed diagnosis/chronic tears

Bucket Handle Resection Technique

  1. Reduce the tear
  2. Detach anteriorly
  3. Perform a crocodile roll
  4. Detach towards the posterior horn

Meniscal Repair

  • 75-90% good results when performed in correct indications
  • Preferred in young patients with large (especially lateral) tears
  • Best candidates:
    • Young patients
    • Red-Red zone (peripheral) tear
    • Longitudinal tear >1cm (even a bucket handle if well reduced)
    • Acute diagnosis
    • Early surgery
  • If ACL injury present:
    • Repair with associated ACL reconstruction – success 90%
    • Repair without ACL reconstruction – success 30%
    • Repair in a knee without ACL tear – success 80%
    • Conclusion: ACL tears and meniscal repairs together are more successful than meniscal repair alone.

Techniques of Repair:

  • Open: For posterior horn tears

  • Inside-out: Gold standard with vertical mattress sutures

  • Outside-in: For anterior horn tears

  • All-inside: Uses stents and absorbable sutures – less NV injury, but not proven to be better than inside-out with vertical mattress

  • Repair Techniques:

    • A: Open repair of medial meniscus (right knee)
    • B: Outside-in repair of medial meniscus (right knee)
    • C: Inside-out repair of lateral meniscus (right knee)
    • D: All-inside repair of lateral meniscus (right knee)

Meniscal Transplantation

  • Allograft meniscus for large resections in young patients, especially on the lateral side
  • Best results when fixation is with a bone block
  • Poor results if:
    • ACL deficient
    • Malalignment
    • Osteoarthritis (OA) present

Discoid Meniscus

  • Typically lateral
  • Typical symptom: Popping in extension in a young person
  • Classification:
    • Type 1: Incomplete
    • Type 2: Complete
    • Type 3: Wrisberg variant (detached at posterior horn)
  • Meniscofemoral ligaments are the only structures holding the meniscus down – amenable to repair
  • Typical X-ray findings:
    1. Increased lateral joint space
    2. Squaring of LFC
    3. Cupping of lateral plateau
    4. Hypoplastic lateral tibial spine

Management:

  • Saucerization: Shape to accommodate LFC
  • Resection of tears
  • Repair of Wrisberg variant (type 3)
  • Nothing if incidental finding

Meniscal Cysts

  • Associated with lateral meniscal horizontal cleavage tears
  • Fluctuating cystic area at the lateral joint line associated with pain
  • Treatment: Treat the underlying tear
    • Decompress cyst from inside out

Baker’s Cyst (Popliteal Cyst)

  • Usually between the gastrocnemius medial head and semimembranosus
  • Associated with chronic degenerate medial posterior horn tears
  • Treating the tear usually resolves the cyst
Back to top