Unstable discoid lateral meniscus

Case contributed by Dr Joachim Feger


Knee twisting injury. Now locking and pain on knee flexion and sometimes an audible noise during movement.

Patient Data

Age: 10 years
Gender: Female


Small knee joint effusion.

Intercondylar region:

  • unremarkable anterior and posterior cruciate ligaments

Medial compartment:

  • unremarkable cartilage and medial meniscus
  • normal medial supporting structures and ligaments

Lateral compartment:

  • small discoid lateral meniscus with horizontal cleavage tear and anterior shift
  • anteroinferior meniscopopliteal ligament not readily definable
  • posterosuperior meniscopopliteal ligament visible but ill-defined
  • very thin meniscofemoral ligament of Wrisberg

Patellofemoral compartment:

  • unremarkable retro-patellar and trochlear cartilage


Discoid lateral meniscus with horizontal cleavage tear, anterior shift and suspected meniscocapsular detachment.

Annotated image

Key findings:

  • discoid lateral meniscus with horizontal cleavage tear and anterior displacement (red arrowhead)
  • an increased amount of fluid between the discoid meniscus and the posterior capsule (blue measurement)
  • anteroinferior meniscopopliteal ligament is not visible, instead there is a small stump (blue arrow)
  • visible but ill-defined posterosuperior meniscopopliteal ligament (purple arrow)

Case Discussion

Discoid meniscus does not require treatment as long as patients are asymptomatic or they have only minor symptoms 7,8.

However, this patient suffers pain and has clinical symptoms after a twisting injury.

MRI shows a discoid lateral meniscus with a horizontal cleavage tear and anterior displacement which is indicative of instability and a meniscocapsular tear and should be treated 9.

The condition has to be differentiated from the variant of an unstable Wrisberg type discoid lateral meniscus, where the meniscofemoral ligament of Wrisberg is the only stabilizing attachment 3,5

Arthroscopy was recommended. Unfortunately, the patient did not follow up with her referring physician and we lost track of her.

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