OBJECTIVETo analyze the clinical and radiological characteristics of hip joint synovial cyst, and to study the main causes and the early economical effective ways for diagnosis.

METHODSTwenty-five patients with hip joint synovial cyst were studied in this research, including 16 males and 9 females aged from 14 to 76 with an average age of 52.8 years old (4 cases from clinical treatment from 1999 to 2007; 1 case searched with keyword "synovial cyst" and "hip" on CNKI form 1978 to 2002, 20 cases searched with keyword synovial cyst and hip on the Medline. The clinical manifestation of 25 cases were painless mass at medial of groin middle point and lower limb venous insufficiency. Synovial cysts of the hip joint were diagnosed by ultrasonography, computer tomography (CT) or nuclear magnetic resonance (MRI). All cases were analyzed retrospectively on the cause of a diseace, clinical features and radiological examinations.

RESULTSThe possible causes of this disease included rheumatoid arthritis in 8 cases, osteoarthritis in 1, total hip replacement in 3, hip tramatic in 3, femoral head necrosis in 2 and unknown origin in 9. The main clinical features included painless groin mass in 9 cases; compression of the common femoral and external iliac veins (lead to outflow obstruction and leg swelling) in 7 cases; inguinal swelling in 5 cases; deep vein thrombosis (DVT) in 3 cases; compression of artery in 1 case. The correct preoperative diagnosis were made by ultrasonography or combined with colour duplex Doppler ultrasonography (CDDS) in 13 cases; CDDS combined with CT in 8 cases; CDDS combined with CT and MRI in 2 cases; articular cavity visualization in 1 case; puncture herniography in 1 case.

CONCLUSIONThe hip joint synovial cyst is mainly caused by the chronic inflammation of the hip joint. As the disease is extremely rare and asymptomatically, precise diagnoses are difficult and and often delayed. More attentions should be paid because of its severe complications. CDDS is an economical effective way for early diagnosis.