[Ultrasonography in serous coxitis].

Ultrasonography is a rapid, reliable and painless technique for diagnosis of transient synovitis and other conditions with effusion of the hip joint. We therefore recommend ultrasonography as the primary imaging method in all patients with acute and subacute pain in the hip and thigh. The diagnostic criterion for intracapsular effusion is a side difference greater than or equal to 2.0 mm in the distance between the anterior joint capsule and the femoral neck. Ultrasonography is also useful in following the resorption of the effusion during the active stage of transient synovitis and in assessing the hip joint for possible development of coxa magna and Legg-Calvé-Perthes disease at later follow-up. Radiography and scintimetry may be omitted in uncomplicated cases but should be employed when Legg-Calvé-Perthes disease is suspected.