647 COMMUNICATIONS Synovial Hemangioma of the Knee Sir: Synovial hemangioma is a rare joint lesion which, among the 96 reported cases,1-15 recurred most frequently in the knee. The patient i s usually an adolescent or young adult who complains of recurrent, transient swelling of the joint, causing painful limitation of motion, limp, and diffuse joint tenderness. Roentgenograms are normal, but joint aspiration, if performed, produces heavily blood-stained synovial fluid. Surgery has been regularly required for definitive diagnosis but that this can be reached preoperatively is demonstrated by the following case report. Case report. MIS. H.H., age 37, gave a long history of repeated episodes of painful swelling of the right knee. The first attack consisted of sudden popliteal pain with rapidly progressive diffuse joint swelling which lasted for 2 days. During the ensuing 10 years she experienced 20 to 30 similar episodes, all unrelated to trauma but of progressively longer duration. The most recent episode had lasted for a month. Between attacks, examination showed the knee was entirely normal. On examination, there was a full range of active and passive knee flexion with normal muscle power and no instability. The joint contained a moderate amount of fluid, and there was no crepitus. Manipulative tests for meniscus injury were negative. Aspiration of the affected knee, on 2 successive days, produced 50 ml. of almost pure blood. All routine laboratory tests for bleeding diatheses and arthritis were normal, as were roentgenograms. A positive contrast arthrogram was normal, and femoral arteriography provided no additional information. On the basis of the characteristic history and by exclusion of other causes of hemarthrosis, a diagnosis was made of synovial hemangioma of the right knee, and this was confirmed at operation when a 2 x 2 X 1.5 cm., bright red, “raspberry” lesion was found immediately upon entering the joint through a medial parapatellar incision (Fig. 1). The lesion was excised with a small margin of normal synovium. Postoperative recovery of joint function was satisfactory, and in the succeeding 20 months there has been no episode of pain and swelling in the knee. Pathological examination showed that the excised tissue was 2.5 cm.across and 1.5 cm.thick, and consisted of a poorly circumscribed 1 cm. nodule of pink, firm tissue surrounded by fat. The interior of the nodule was filled with dark red, clotted blood. As seen in histological preparations, the bulk of the nodule was made up of tortuous, Fig. 1.-Operative (arrow). photograph of lesion distended, venous channels containing occasional clumps of erythrocytes (Fig. 2). Some segments of the vein walls were thickened by organized adherent thrombus, and there were areas of recent hemorrhage together with old blood pigment in the intervening areolar connective tissue. The surface of the nodule was covered with hyperplastic, chronically inflamed synovial membrane. Synovial hemangioma is a rare cause of recurrent hemarthrosis. This case, remarkable because a firm preoperative diagnosis was made, is reported here. JACKSTEVENS,M.D. PAULL. KATZ, M.D. L. ARC-, M.D. FRANCIS DANIELJ. MCCARTY, M.D. Chicago, Illinois 648 COMMUNICATIONS Fig. 2.-Low-power right. H E X 75. + photomicrograph of resected specimen. Synovial surface to the REFERENCES 1. Bennett, G. E., and Cobet, M. C.: Hemangioma of joints. Arch. Surg. 38:487, 1969. 2. Brodsky, A. 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