Introduction:
Rare benign vascular malformation
Usually seen in children and young adults
Most commonly affects knee
Present with joint pain, swelling, spontaneous hemarthrosis
Radiograph:
Nonspecific soft tissue mass with phleboliths
MR:
Pathognomonic lobulated intraarticular mass with intermediate signal on T1 and marked high signal on T2 due to pooling of blood within vascular spaces; low signal linear structures throughout lesion on T2 due to fibrous septa/vascular channels
Treatment:
Surgical excision. Recurrence is common
References:
Sheldon PJ et al. Imaging of Intraarticular Masses. RadioGraphics 2005;25:105-119
