Parameniscal cyst

Case contributed by Mostafa Elfeky
Diagnosis probable


Medial knee swelling.

Patient Data

Age: 50 years
Gender: Female

Knee joint osteoarthritis, seen as narrowing of medial tibiofemoral joint compartment with marginal osteophytes and subchondral sclerosis. Vaccum effect is seen along the medial tibiofemoral joint compartment suggestive of degenerated medial meniscus.

A homogeneous dome-shaped opacity is noted related to the medial aspect of the knee joint.


Osteoarthritic changes, seen as narrowed medial tibiofemoral joint compartment and marginal osteophytes. Chondral defect with underlying bone marrow edema is noted at the medial aspect of medial tibial plateau.

Medial meniscus is extruded with intrasubstance high T2 signal intensity not reaching articular surfaces, suggestive of meniscal degeneration.

A dome-shaped well-defined cystic lesion with fluid intensity is seen at the medial aspect of the knee with septations, suggestive of a parameniscal cyst. 

Case Discussion

A parameniscal cyst is a focal joint fluid collection adjacent to a meniscus that usually shows degeneration or tear. Direct communication with the meniscal tear may not be identified on MRI.

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