A and B, Plain radiographs of a patient with pigmented villonodular synovitis do not show any soft-tissue abnormality. T1-weighted (sagittal) (C) and T2-weighted (axial) (D) MR images demonstrate a diffuse intraarticular process that is dark on both sequences. E, Intraoperative photograph shows diffuse pigmented villonodular synovitis of the knee.