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Pigmented Villonodular Synovitis (PVNS) in an infrequent tumoral like disease and there are only a few MRI studies published. Concerning our series of five cases compared with the literature, the readers attention is drawn to the etiologies still under debate and to the respective contribution of the different imaging methods. MRI known for its high sensibility, but also for its low specificity in tumoral pathology, has turned out to be, in the case of PVNS, quite remarkable in both regards. The RMI aspect is quite well correlated to the histological structure of this synovial hyperplasia and to its evolution: highly vascular mass at the beginning and then low cellular density stroma, fibrous, with deposition of hemosiderin. In our five cases, as in almost all those previously reported in the literature, MR imaging shows heterogeneous areas of decreased signal intensity on T2 weighted sequences and on two of our cases after administration of gadolinium. Still the same MR aspects can be found in rheumatoid, hemophilic arthritis, as well as synovial chondromatosis, and therefore the clinical background and findings as well as plain films become essential. MR imaging should be the first examination to be undertaken after plain films, leading in most cases to a precise local preoperative assessment.