A full-term, small-for-gestational-age, neonate was born 4 days after
rupture of the membranes. On the 5th day of life, she developed sepsis
due to Klebsiella pneumoniae. On the 18th day of life, the right hip
was noted swollen with limited range of motion, but it was painless on
passive movements. Ultrasonography revealed abscess of the right ilio
-psoas muscle with normal appearance of the right hip joint. Surgical
incision and drainage and antibiotic administration resulted in a grad
ual full recovery. Ultrasonography can confirm the diagnosis of this e
xceptional clinical entity in neonates, which is difficult to differen
tiate from septic arthritis of the hip.