Broad disc like configuration with loss of normal bow-tie
Considered congenital and frequently bilateral Thickness 5-13 mm (usually more than 13mm)
Incidence:
More common in LM. LM 1.5-15%, in MM 0.3%
Variant:
Anterior megahorn discoid meniscus
Pathology:
Susceptible to tears and cysts
Clinical features:
Most commonly present in adolescence, but most are asymptomatic
Complaints: pain, slipping, snapping, locking
Classification (Watanabe):
Complete: extends into intercondylar notch
Incomplete: does not extends into intercondylar notch. Most common
Wrisberg-ligament type: lacks posterior capsular attachment (posterior meniscotibial ligament) and occurs only in LM.
Plain radiograph:
Wide lateral joint space
Hypoplastic and squared-off lateral femoral condyle
High fibular head
Cupping of lateral tibial plateau
MR:
Sagittal (4-5mm thick slices):
Bow-tie in 3 or more images
No central tapering
Increased height
Coronal:
Increased height, more than 2 mm higher than the opposite meniscus
Extension into intercondylar notch
Radial diameter more than 13 mm
