Hemarthrosis is known to occur with various etiologic factors, including trauma, proliferative synovial tissue entrapment, hypervascularization of joint components, and coagulation disorders such as hemophilias. Hemarthrosis is reported in up to 1.6% of patients who have undergone total knee replacement. Recurrent hemarthrosis is primarily associated with coagulation defects in children; however, in adults it is most frequently associated with ligament rupture, if not related to any trauma. Spontaneous hemarthrosis has been rarely reported with findings of lateral meniscal degeneration and central bone marrow lesions in osteoarthritis patients. The author reports on a case of spontaneous hemarthrosis in a 72-year-old patient without traumatic history

• Hyun Sook Kim(Department of Internal Medicine, College of Medicine, the Soonchunhyang University Seoul Hospital) Corresponding author