[MR imaging of pigmented villonodular synovitis of knee]

Six cases of pigmented villonodular synovitis (PVNS) of the knee are presented. MR images and surgical findings were available in all cases. Four of six cases were diffuse form, and the other two were localized form. The MR appearance of PVNS varied, depending on the relative proportion of the pathological component. It most commonly consisted of scattered areas of low signal intensity due to hemosiderin deposition in the hypertrophied synovium on T2*-weighted images, and dotted areas of low signal intensity presumably resulting from the fibrous component of the lesion on T1-weighted images. The latter finding was described for the first time in our study. One case was associated with osteochondromatosis and osteoarthritis, and another case with osteoarthritis. In the remaining four cases, the osseous structures, cruciate ligaments and menisci were normal.