Geodes, also known as subchondral cysts, are well-defined lytic lesions at the periarticular surfaces. A geode is one of the common differential diagnoses of an epiphyseal lesion (lytic).

Geodes are seen in a small group of disorders including:

Presumably, one method of geode formation takes place when synovial fluid is forced into the subchondral bone, resulting in a cystic collection of joint fluid. Another etiology is that following a bone contusion, the contused bone forms a cyst.

They rarely cause problems by themselves but are often misdiagnosed as something more sinister and an unnecessary biopsy of a geode might be performed on the basis of the differential of an epiphyseal lesion.

Geode is a term borrowed from "geology", where it refers to rounded formations in igneous and sedimentary rocks.

Article information

rID: 21095
Synonyms or Alternate Spellings:
  • Geodes
  • Subchondral cyst
  • Subchondral cysts
  • Geode formation

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Cases and figures

  • Case 1
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  • Case 2: on knee MRI
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  • Case 3
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