Subsynovial vascular abnormality causing recurrent hemarthrosis in an 84-year-old man

We describe a patient with recurrent hemarthrosis of one knee. Investigation demonstrated a vascular abnormality of the synovium as the likely cause. Structural abnormalities of the synovial vasculature should be considered, in the absence of a systemic cause, as a potential source of bleeding in older patients with recurrent hemarthrosis.