The irritable hip syndrome, otherwise known as transient synovitis or observation hip, is a characteristic symptom complex of hip or knee pain, limp and spasm, usually acute in onset. Resolution without long-term sequelae is the typical clinical course, although Perthes' disease can present with similar features. Metaphyseal abnormalities alone following irritable hip syndrome have not been previously described. This paper reports two patients who suffered focal growth arrest of the proximal femoral metaphysis following the irritable hip syndrome without evidence of epiphyseal damage.A boy aged 2 years and 8 months presented with acute onset, left irritable hip with no history of local trauma or recent infection. Radiology of the left hip showed a 2 mm increase in width of the medial joint space and metaphyseal irregularity (Fig. 1A). A blood count showed a slight leucocytosis (WCC 13.7), with an ESR of 13. The condition settled over the next seven days without antibiotics and at that time the blood count was repeated and showed a return to normal (WCC 7,000; ESR—12).Hip arthrography was normal. The child remains well clinically but serial radiographs during the next 18 months showed progression of the central metaphyseal defect with a clear zone of demarcation some distance from the metaphysis followed by new bone formation and consolidation. (Figs. 1B, c). There is, after two years, residual shortening of 1 cm (acetabular-trochanteric distance) and widening of 0.4 cm of the femoral neck compared with the contralateral, normal side.