RESUMEN
Synovium is specialized mesenchymal tissue lining the inner surface of the joint capsule and is the site for a series of pathologic processes that are characteristic, and in some cases specific, to this distinctive tissue. Hemosiderotic synovitis is a rare and inadequately defined synovial proliferative disorder, which develops with recurrent hemorrhages in the joint. The most affected joint from bleeding is the knee whatever the etiology is. Repeated hemarthrosis may produce significant structural alteration of joints leading to chronic osteoarthritis. The most common cause is hereditary clotting factor deficiency diseases like hemophilia. We report a rare case of nonhemophilic hemosiderotic synovitis of the knee joint, in which the patient lacks history of any bleeding diathesis. Its definitive diagnosis was possible only by histopathological examination. The prompt recognition of this distinct subtype of hemosiderotic synovitis and awareness of underlying causes should lead to earlier diagnosis, appropriate therapy, less joint destruction, and better outcomes.