Geode (or subchondral cyst) is a well-defined lytic lesion in the periarticular surfaces. A geode is one of the common differential diagnoses of an epiphyseal lesion (lytic).
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 aetiology is that following a bone contusion, the contused bone forms a cyst.
Geodes are seen in a variety of disorders including:
- degenerative joint disease (DJD) 1, 3
- rheumatoid arthritis 2
- calcium pyrophosphate dihydrate crystal deposition disease (CPPD) 4
- avascular necrosis 4
Treatment and prognosis
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.
History and etymology
Geode is a term borrowed from geology, where it refers to rounded formations in igneous and sedimentary rocks.
- 1. Brant WE, Helms CA. Fundamentals of diagnostic radiology. Lippincott Williams & Wilkins. (2007) ISBN:0781765188. Read it at Google Books - Find it at Amazon
- 2. Moore EA, Jacoby RK, Ellis RE et-al. Demonstration of a geode by magnetic resonance imaging: a new light on the cause of juxta-articular bone cysts in rheumatoid arthritis. Ann. Rheum. Dis. 1990;49 (10): 785-7. Free text at pubmed - Pubmed citation
- 3. Jacobson JA, Girish G, Jiang Y et-al. Radiographic evaluation of arthritis: degenerative joint disease and variations. Radiology. 2008;248 (3): 737-47. Radiology (full text) - doi:10.1148/radiol.2483062112 - Pubmed citation
- 4. Resnick D, Niwayama G, Coutts RD. Subchondral cysts (geodes) in arthritic disorders: pathologic and radiographic appearance of the hip joint. AJR Am J Roentgenol. 1977;128 (5): 799-806. AJR Am J Roentgenol (abstract) - Pubmed citation