Localized Pigmented Villonodular Synovitis of the Knee Joint: A Case Report and Literature Review

The incidence rate of PVNS, which is synovium tissue as nodules or pedunculated masses, is low however, the localized type is even less. We reported a case of the unusual properties of LPVNS located in the knee. A 32-year-old man presented to our clinic with pain and mechanic symptoms in his right knee. Magnetic resonance imaging (MRI) showed an intra-articular mass in the infrapatellar area of the knee adjacent to the Hoffa fat pad close to femoral trochlea groove. The mass was hypo intense in the T1 sequence and heterogeneously hypointense in the T2 sequence as well, which was considered as a local type of tenosynovial giant cell tumor (LPVNS). Excision was carefully performed without penetrating the tumor. The gross appearance of the tumor was yellow-reddish and brown in color. Histopathologic examination revealed pigmented villonodular synovitis of the local type. Localized Pigmented Villonodular Synovitis (LPVNS) is a very rare disease and it is silent and insidious, symptoms are non-specific, nevertheless, differentiation diagnosis should be keeping this entity in mind. Even though the LPVNS of the knee is an uncommon intra-articular presenttion, overlook this lesion based on imaging findings is an import approach for diagnosis of LPVNS, and arthroscopy assisted excision is an option for management of the LPVNS if doing it appropriately.