[The subchondral synovial cyst (intraosseous ganglion)].

Twelve cases of subchondral synovial cysts (intra-osseous ganglion) have been seen and their clinical features, radiological findings and differential diagnosis are described. The lesion is a benign cystic tumour-like mass in the subchondral portion of a synovial joint. Our findings in respect of age, sex and localisation are compared with those of other authors. The aetiology and pathogenesis of the lesion is not completely understood. There is an increased incidence in middle life and joints with high dynamic and static stress are favoured, particularly in the lower extremities. Chronic stress or microtrauma, causing damage to the involved joint, therefore appears to be a plausible explanation.