Gas-containing ganglia of the hip.

Three cases of ganglia related to the hip containing gas are presented. Gas may be shown by conventional radiography, linear tomography or computed tomography. All three cases had advanced degenerative disease of the joint. In degenerative disease, ganglia form through a pathway which allows the transfer of intra-articular gas into the ganglion. It is important to differentiate this phenomenon from overlying bowel gas and other causes of gas within soft tissues. It is the most specific radiological feature of ganglia around the hip.