10b - Answer: 57-year-old male presents with medial right knee pain

History: This 57-year-old male presents with medial right knee pain. The pain has persisted for eight months.

MOST LIKELY DIAGNOSIS: Parameniscal pseudocyst

Using the diagnostic web viewer, we have provided images that assist in telling our clinical story. Areas of significance are indicated below.

CLINICAL CONSIDERATIONS:

This is a 57-year-old male presents with medial right knee pain. The pain has persisted for eight months. Do you favor capsulosynovial cyst, ganglion pseudocyst or parameniscal pseudocyst of meniscal origin? What sign clinches the diagnosis? How many different characteristics can you name that differentiate the natural history of lateral meniscus cyst / pseudocyst of meniscus origin versus medial meniscus cyst / pseudocyst of meniscus origin?

You should favor parameniscal pseudocyst of meniscal origin. The meniscal arrow sign should clinch the diagnosis. To explain it another way, the meniscus has a tail (arrow) that bisects the meniscus as an area of bright signal communicating from the cyst to the very center of the meniscus and this meniscal signal points directly to the center of the cyst (arrow) which straddles it.

As far as the characteristics, lateral meniscus cysts are more common, usually smaller, usually more painful, and less likely to migrate from one locale to another.

The medial meniscus cyst may be silent and therefore more often painless, more often giant, have a tendency to extend from the midbody to the posterior quadrant, and be more likely to migrate or extend distantly.

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Content reviewed: November 3, 2021