Discoid Meniscus

Topic updated on 05/21/16 6:15pm

Sagital MRI images in the lateral compartment with 3 or more slices with the "bowtie" sign is indicative of a discoid meniscus.
  • Abnormal development of the meniscus leads to a hypertrophic and discoid shaped meniscus
    • discoid meniscus is larger than usual
    • also referred to as "popping knee syndrome"
  • Epidemiology
    • incidence
      • present in 3-5% of population
    • location
      • usually lateral meniscus involved
      • 25% bilateral
Watanabe Classification
Type I  • Incomplete

Type II  • Complete

Type III  • Wrisberg (lack of posterior meniscotibial attachment to tibia
  • Symptoms
    • pain, clicking, mechanical locking 
    • often becomes symptomatic in adolescence
  • Physical exam
    • mechanical symptoms most pronounced in extension
  • Radiographs
    • recommended views
      • AP and lateral of knee
    • findings    
      • widened joint space due to widened cartilage space (up to 11mm)
      • squaring of lateral condyle with cupping of lateral tibial plateau
      • hypoplastic lateral intercondylar spine
  • MRI
    • indications
      • study of choice for suspected symptomatic meniscal pathology
    • findings
      • diagnosis can be made with 3 or more 5mm sagittal images with meniscal continuity  ("bow-tie sign")
      • sagittal MRI will show abnormally thick and flat meniscus 
      • coronal MRI will show thick and flat meniscal tissue extending across entire lateral compartment 
  • Nonoperative
    • observation
      • indications
        • asymptomatic discoid meniscus without tears  
  • Operative
    • partial meniscectomy and saucerization    
      • indications
        • pain and mechanical symptoms
        • meniscal tear or meniscal detachment
      • technique
        • obtain anatomic looking meniscus with debridement 
        • repair meniscus if detached (Wrisberg variant)


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Qbank (7 Questions)

(OBQ07.129) An 11-year-old soccer player presents with a 6 month history of snapping and discomfort along the lateral joint line of the knee. Examination shows a 10 degree loss of active extension. An AP radiographs is shown in Figure A. Sequential sagittal MRI images of the lateral compartment of the knee are shown in Figure B. What is the most appropriate course of action? Topic Review Topic
FIGURES: A   B        

1. Physical therapy with a focus on concentric knee strengthening
2. Non-weightbearing for 6 weeks
3. Arthroscopic saucerization of the lateral meniscus and/or meniscal repair
4. Open lateral meniscectomy
5. Arthroscopic microfracture treatment of the defect on the lateral femoral condyle

(OBQ05.166) An 8-year-old boy was playing at school and took a direct blow to his knee causing pain and swelling. His pediatrician ordered an MRI which is shown in Figure A. The patient was referred to your office for a consultation. He denies any past history of pain, clicking, or locking. His knee exam is unremarkable. Radiographs of the knee in your office are normal. What course of action will you recommend? Topic Review Topic
FIGURES: A          

1. Surgical debridement and repair
2. Ligamentous reconstruction
3. Casting in 45 degrees of flexion
4. Knee immobilizer and non weight bearing for 6 weeks
5. Observation

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Video (no audio) shows saucerization of a discoid lateral meniscus.
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