Synovial hemangioma of the hip joint with pathological femoral neck fracture and extra-articular extension.

Synovial hemangioma is a rare benign intra-articular vascular tumor that mostly occurs in the knee joint (97%); only one case of synovial hemangioma in the hip joint has been reported [1–7]. The common symptoms of synovial hemangioma are persistent pain, limitation of motion, painful joint swelling, nontraumatic recurrent hemarthrosis, and progressive joint destruction due to nontraumatic recurrent hemarthrosis on occasion. Although aggressive intraand extra-articular extensions invading adjacent bone and soft tissue structures have been reported in some cases of synovial hemangioma in the knee joint, no cases of severe bone destruction resulting in pathological fracture have been reported [1–5, 8, 9]. The clinical features of synovial hemangioma in the hip joint are not well understood because it is very rare and presents different anatomical characteristics from synovial hemangioma in the knee [7]. Herein, we report a case of invasive synovial hemangioma of the hip with pathological femoral neck fracture and extra-articular extension, and discuss the clinical features of this condition.