Ultrasonography in hip joint effusion. Report of a child with transient synovitis.

In a 7-year-old boy with clinical symptoms of transient synovitis of the hip, an intracapsular effusion was diagnosed with computed tomography and ultrasonography. An intracapsular pressure of 50 mmHg was recorded prior to aspiration of 5.5 ml of clear fluid. Repeated ultrasonography immediately after aspiration verified a reduction in effusion, and serial examinations on the following days did not reveal any recurrence of the effusion.