Diffuse pigmented villonodular synovitis of the knee joint: 3-year follow-up of a case report.

Pigmented villonodular synovitis (PVNS) is a proliferative, recurrent and locally invasive disease of the synovium. The symptoms of the disorder are not typical and thus it is very often misdiagnosed. Most of the times, magnetic resonance imaging presents the nodular model of development and sets the basis for the diagnosis. The final diagnosis will be set by the pathological evaluation of the lesion's biopsy. PVNS may be localized (nodule with a clear boundary with/without presence of single pedicle) or diffuse (extensive involvement of the adjacent nerves and vessels). Depending on the extension of the PVNS, a different management approach is performed, lesion excision vs. resection, followed by radiotherapy respectively. We report a case of diffuse PVNS in the knee joint, treated with surgical excision and adjuvant radiotherapy as well as follow-up imaging after a time period of 3 years.