Hemangioma or vascular malformation of the synovium is rare and presents a difficult problem in diagnosis and treatment. A long history of joint pain and recurrent non-traumatic hemarthrosis usually draws attention to the hemangioma of the knee joint. The lesion can be seen in two different formations; the synovial hemangioma or the arteriovenous malformation named as hemangiohamartomas, both of which involve the synovium and cause non-traumatic episodes of hemarthrosis. MRI scanning together with arthroscopy is a diagnostic tool to demonstrate the extent and the nature of the lesion. We treated the three patients at different ages. All patients underwent standard radiographic examination, CT scans, MRI and diagnostic arthroscopy. After frozen section taken via arthroscopically, the lesions were excised by arthrotomy. The mean follow-up was 38 months (31-45) and all patients are asymptomatic postoperatively. Three additional cases and a review of the literature are presented because of the rarity of the lesion.