Updated: 8/9/2021

Discoid Meniscus

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  • Summary
    • A discoid meniscus is the abnormal development of the meniscus leading to a hypertrophic and discoid shaped meniscus.
    • Diagnosis can be suspected on radiographs with (squaring of lateral condyle with cupping of lateral tibial plateau) but require MRI for confirmation (3 or more 5mm sagittal images with meniscal continuity).
    • Treatment is generally observation for patients who are asymptomatic. Arthroscopic meniscectomy and saucerization may be indicated for patients with continued pain and mechanical symptoms.
  • Epidemiology
    • Incidence
      • common
        • present in 3-5% of population
    • Anatomic location
      • usually lateral meniscus involved
      • 25% bilateral
  • Etiology
    • Pathophysiology
      • failure of apoptosis in utero
  • Classification
    • Watanabe Classification
      Type I
      Complete
      Type II
      Incomplete
      Type III
      Wrisberg (lack of posterior meniscotibial attachment to tibia)
  • Presentation
    • Symptoms
      • pain, clicking, mechanical locking
      • often becomes symptomatic in adolescence
    • Physical exam
      • mechanical symptoms most pronounced in extension
  • Imaging
    • Radiographs
      • recommended views
        • AP and lateral of knee
      • findings
        • widened joint space (up to 11mm)
        • squaring of lateral condyle
        • 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
        • Symptomatic cases may reveal underlying meniscus tear
  • Treatment
    • 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)
        • meniscal instability is frequently present
          • recent literature suggest anterior horn instability is most common

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(SBQ16SM.13) A 12-year-old basketball player reports frequent and moderately painful popping in his left knee during his games. His symptoms have remained persistent and both he and his parents are concerned as this limits his performance. He is evaluated and the decision is made to proceed with arthroscopic saucerization. Which of the following is true of his pathology?

QID: 211249
1

Incomplete is more common than complete type

31%

(569/1864)

2

Instability of the meniscus is uncommon

9%

(164/1864)

3

Long-term degenerative changes are similar between arthroscopic saucerization, partial, and complete meniscectomy

6%

(105/1864)

4

Saucerization with repair results in inferior clinical outcomes compared to saucerization alone

6%

(121/1864)

5

A 6-8mm peripheral rim is recommended following saucerization

47%

(884/1864)

L 4 A

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(SBQ13PE.9) A 6-year-old boy complains of a 'clunking' sensation in his left knee. He has no associated pain and denies trauma. He can elicit the sensation when moving his knee from flexion into full extension. He is otherwise healthy, with no birth or developmental issues. On examination, there is a palpable clunk felt over the anterior knee through range of motion. There is no obvious instability or tenderness and he had normal patellar tracking. An AP radiograph of the knee is shown in Figure A. What would be the most likely diagnosis?

QID: 4943
FIGURES:
1

Agenesis of the anterior cruciate ligament

3%

(105/4050)

2

Thickened medial plica

22%

(906/4050)

3

Grade IV chondral flap

1%

(52/4050)

4

Pigmented villonodular synovitis

1%

(35/4050)

5

Abnormal meniscal morphology

72%

(2908/4050)

L 3 C

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(SBQ13PE.10) Which statement is true regarding discoid menisci?

QID: 4947
1

Most commonly involves the medial meniscus

5%

(163/3428)

2

Bilateral in >75% of cases

6%

(220/3428)

3

Asymptomatic discoid meniscus should undergo saucerization

1%

(36/3428)

4

Radiographs will commonly show a hyperplastic lateral intercondylar spine

3%

(117/3428)

5

Radiographs will commonly show squaring of affected condyle with cupping of tibial plateau

84%

(2865/3428)

L 2 B

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(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?

QID: 790
FIGURES:
1

Physical therapy with a focus on concentric knee strengthening

12%

(246/2137)

2

Non-weightbearing for 6 weeks

3%

(66/2137)

3

Arthroscopic saucerization of the lateral meniscus and/or meniscal repair

83%

(1769/2137)

4

Open lateral meniscectomy

1%

(17/2137)

5

Arthroscopic microfracture treatment of the defect on the lateral femoral condyle

1%

(27/2137)

L 2 C

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(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?

QID: 1052
FIGURES:
1

Surgical debridement and repair

4%

(114/2754)

2

Ligamentous reconstruction

1%

(22/2754)

3

Casting in 45 degrees of flexion

2%

(62/2754)

4

Knee immobilizer and non weight bearing for 6 weeks

5%

(131/2754)

5

Observation

88%

(2414/2754)

L 1 D

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CASES (1)
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