ObjectivesTo investigate the ultrasound findings of the synovial hemangioma of knee (SHK) and to evaluate its value in clinical diagnosis.MethodsThe ultrasonographic manifestations and clinical data of 10 patients with SHK confirmed by surgery and pathology were retrospectively analyzed and compared with MRI findings, surgery and pathological results.ResultsSeven cases of SHK (6 cases of diffuse type, 1 case of limited type) were assessed by ultrasound, including 1 case of vascular origin, 1 case of supraorbital sac origin, 1 case with pigmented villonodular synovitis, 1 case with thrombosis, 2 cases accompanied with bone erosion and osteophyte formation, and 3 cases with joint cavity effusion. Ultrasonic findings of SHK were as followed: 7 cases of SHK were manifestate as diffuse mass with unclear boundary, irregular shape and uneven echo mass; 5 cases had mixed-echo mass with reticular structures inside, an increased volume in erect position and positive CDFI compression test; 1 case had heterogeneous hypoechoic mass with a nodular appearance and the positive compression test; 1 case as poorly-demarcated, irregular shape, heterogeneous hyperechoic mass without obvious blood flow signals under the compression test. There were no characteristic ultrasonic findings from other 3 cases of SHK.ConclusionsDiffuse SHKs have characteristic ultrasonograms. SHKs with localized and significant synovial hyperplasia have no specific ultrasonic manifestation and are easily misdiagnosed. Ultrasound is convenient, noninvasive and inexpensive. It can accurately evaluate the involvement of knee joint capsule and surrounding soft tissues. It can be used as the first line diagnostic modality for routine scanning of SHKs.