Paraffinoma of the knee.

We present the case of a 90-year-old man with a swollen, painful knee and a history of paraffin injections. Radiography showed soft tissue streaky and nodular calcifications without erosions. MR imaging showed globular areas of low signal intensity on T1- and T2-weighted images which became even more hypointense on STIR sequences, and an infiltrative hypointense region containing areas of high signal on T1-weighted, T2-weighted and STIR images. Biopsy confirmed soft tissue foreign body granulomata, fibrous reaction and areas of inflammation. We believe this to be the first report of MR imaging of paraffinoma outside the breast.