[Coxitis fugax--the beginning of Perthes' disease?].

We present the clinical case of a decennial boy with acute leftsided hip pain without appropriate trauma. The initial diagnosis of coxitis fugax was verified in this case with inconspicuous blood parameters and X-ray by a sonographically proven intraarticular effusion. An immediate magnet resonance imaging (MRI) study of the affected hip joint was done. Here, a complete "necrosis" of the proximal femur epiphysis was verified. With knowledge of these results, an immediate operation of the hip joint with a ventral capsule incision and consecutive intraarticular decompression was performed. A complete reperfusion of the femur head was evident in the MRI scan seven days postoperatively. In accordance with this clinical case report, we would like to point out the necessity for the immediate diagnosis of indifferent hip pain by means of MRI, especially for patients in the atypical "critical age" (> or = 8 years) for coxitis fugax. This is discussed under consideration of the possible aetiopathogenesis and the current literature.