Occult epiphyseal bone abscess: lessons for the unwary.

Two male children presented with increasing pain in the right knee and constitutional symptoms. Biochemical markers of inflammation were elevated. Plain radiography was reported as normal and bone scintigraphy was consistent with synovitis of the right knee in the first case. The second child underwent aspiration of the knee with drainage of turbid fluid 1 week after antibiotics. Slow response to therapy led to MRI and CT scanning in the second child, revealing an epiphyseal abscess. Review of the scintigraphic studies in the first child raised the possibility of osteomyelitis of the distal right femur. Further imaging was undertaken with MRI and CT scanning confirming an epiphyseal bone abscess. Failure of diagnosis of an epiphyseal bone abscess by combined plain radiography and scintigraphy has not previously been reported and provides a number of valuable lessons.