Objective To discuss the manifestations of MRI of enlarged iliopsoas bursa.Methods MRI features of enlarged iliopsoas buras were studied retrospectively proved by aspiration of synovial fluid under ultrasound guidance or surgical operation-pathology or clinical followed up and with typical MRI findings in 13 cases were analysed retrospectively.Results 13 enlarged iliopsoas bursas all located at the level of or part of the acetabulum sections in only one side(right side in 5 and left side in 8).The largest cyst was 7.0 cm in diameter.All of them appeared as round,oval,upside-down water drop-like or irregular multilocular cystic shadow and located posterolateral to the external iliac blood vessels and or femoral blood vessels,medial to iliopsoas muscle(tendon),and anterior to hip joint capsule.The cysts were hypo-or iso-intensity on T1WI and water-like high signal intensity on T2WI and markedly higher signal intensity on STIR,it was difficult to identify the cystic wall on plain scans.5 cases underwent contrast-enhanced MR scan,the cystic wall had linear slight to moderate homogeneous enhancement in 3,no enhancement in one and irregular multilocular enhancement in one who was with simple purulent synovitis.2 cases were simple synovitis,11 cases accompanied by hip joint disease.Conclusion MRI is of important value in diagnosing the enlarged iliopsoas bursa.