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A 31-year-old woman presented with right groin pain radiating down the medial thigh of 3 months' duration (Figure 1).
Your diagnosis?
DIAGNOSIS: Iliopsoas bursitis. Computed tomography (CT) of the pelvis shows a water attenuation, unenhancing fluid collection posterior to the conjoined iliopsoas muscle tendon (Figure IA). This fluid is within the distended iliopsoas bursa. Axial and sagittal T2 fat saturated magnetic resonance imaging (MRl) shows the fluid filled bursa anterior to the hip joint line and communication with the hip (Figures IB- ID).
Anatomy
The iliopsoas muscle flexes the hip and externally rotates the femur. The ä lìacus muscle originates from the iliac bone and the psoas from the lumbar spine. The two muscles converge to form the iliopsoas muscle, which descends anterior to the pelvic brim and hip capsule, between the anterior inferior iliac spine and Uiopectineal eminence. The muscle passes lateral to the femoral vessels and ultimately inserts as the iliopsoas tendon on the lesser trochanter of the femur.'-2
The iliopsoas bursa is the largest and most constant bursa in the human body.3"7 Bilateral in 98% of people, the iliopsoas bursa normally averages 5-7 cm in length by 2-4 cm in width.1,4,6*9 This bursa lies deep to the iliopsoas tendon and decreases the friction over the anterior hip capsule created by the contracting muscle.3 The normal bursa courses from the inguinal ligament inferiorly to the lesser trochanter, bordered medially by the femoral vessels and laterally by the femoral nerve.2*4,6,10 It ís bound anteriorly by the musculotendinous junction of the iliopsoas muscle and posteriorly by the fibrous hip capsule, between the iliofemoral and pubofemoral ligaments. This posterior boundary of the iliopsoas bursa is the thinnest and most vulnerable aspect of the hip capsule, which facilitates communication of the bursa with the hip space.4,5
Although this finding is normal in up to 15% of individuals,1*4,6,810 intraarticular pathology such as osteoarthritis or rheumatoid arthritis increases the incidence of communication to 30%40%_2.6.9
Iliopsoas Bursitis
Without underlying hip disease, iliopsoas bursitis is probably due to friction of the overlying tendon on the iliopsoas bursa in forceful or vigorous hip flexion and extension.1,4 More commonly, however, iliopsoas bursitis is found in patients with underlying hip pathology (Table 1 ).3-5,8,9,' ' Iliopsoas bursitis is rare in children, and is...