The characterization of "transient synovitis of the hip" in children.

A 30-year retrospective review of 497 cases of transient synovitis of the hip involving 475 children allowed full characterization of the syndrome. Femoral head measurements of 118 patients at follow-up of 6 months showed no significant dimensional changes. Three cases of Legg-Calvé-Perthes disease (2.5%) were found in follow-up, as well as a case of osteoid osteoma of the femoral neck and two cases of juvenile rheumatoid arthritis. Recurrent synovitis with a benign prognosis occurred in 19 patients. In spite of a generally anticipated good prognosis in the vast majority of cases, radiographic assessment at 6 months after the initial episode is recommended.