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 lesions (lytic). This is originally a geological term referring to rounded formations in igneous and sedimentary rocks.
Presumably, one method of geode formation takes place when synovial fluid is forced into the subchondral bone, causing a cystic collection of joint fluid. Another aetiology is following a bone contusion, in which 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.
- 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