Synovial hemangiomas are relatively rare tumors. Clinicians are inclined to delay treatment in most cases. We encountered three cases, in which there was a delay before the patients were operated on. During the relatively long-term postoperative follow up, none of the three cases showed a recurrence of either hemoarthrosis or knee pain. However, limitations in motion or osteoarthritic changes in the affected knee joint remained. We therefore consider that synovial hemangiomas of the knee, even if found in young children, could possibly result in postoperative limitations in motion or osteoarthritic changes.