Concurrence of Pigmented Villonodular Synovitis with Calcium Pyrophosphate Deposition in a Postacute Stroke Patient.

Pigmented villonodular synovitis (PVNS) is a rare synovial proliferative disease featuring hemosiderin deposits. Calcium pyrophosphate deposition (CPPD) is a crystal-induced inflammatory arthritis common in the elderly. We reported the case of a 78-year-old male who was under stroke rehabilitation when acute inflammatory and hemorrhagic knee arthritis of his paretic lower limb occurred. CPPD was proven by synovial analysis. Ultrasonography showed widespread synovial nodular lesions in the affected knee and helped guiding difficult arthrocentesis. These led to a rapid diagnosis of PVNS with magnetic resonance imaging. In elderly stroke patients, knee pain, being a common complaint, warrants a careful diagnosis including adequate imaging. This case demonstrates that ultrasonography is an accessible and useful diagnostic tool.