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As the disease evolves, from the onset of avascular necrosis until complete revascularization of the epiphysis, characteristic changes are visible on plain radiographs. On the basis of these radiographic changes, Waldenstrom divided the disease into four stages; the stages of avascular necrosis, fragmentation, reconstitution and the healed stage. The first three of Waldenstrom’s stages have been further subclassified into early and late phases for each—Stages 1a, 1b, 2a, 2b, 3a and 3b . The average duration for the avascular necrosis, fragmentation, reconstitution stages is approximately 7, 8 and 18 months, respectively, while the duration of the sub-stages in the modified classification is approximately half of these respective durations. This modified staging of the disease is reproducible and of importance in planning treatment. Extrusion of the femoral head—defined by a lateral migration and loss of containment of the proximal femoral epiphysis—commences early in the disease process and gradually increases as it progresses from Stage 1a to Stage 2a. Thereafter, in Stage 2b, there is an abrupt increase in extrusion. Progressive widening of the femoral metaphysis is another phenomenon that is seen in untreated children. The pattern of progression of metaphyseal widening is almost identical to that seen with femoral extrusion; a modest increase in metaphyseal width occurs between Stage Ia and IIa after which there is a sudden increase in the width of the metaphysis. Metaphyseal width has been shown to accurately reflect the extent of epiphyseal flattening ( “mushrooming”) and the ultimate enlargement of the femoral head . The timing of significant metaphyseal widening suggests that irreversible flattening and deformation of the femoral head has already occurred by the late stage of fragmentation or shortly thereafter . Epiphyseal collapse, particularly of the lateral part of the epiphysis (referred to as the “lateral pillar”) is another feature of LCPD that is of prognostic significance. The more the lateral pillar has collapsed, the poorer is the prognosis . Treatment planning based on the extent of epiphyseal collapse outlined by Herring has been popular but its value is limited by the fact that the extent of collapse of the lateral pillar can only be determined in Stage 2b. Waiting until stage IIb to apply the Herring grading and then planning treatment especially in the older child is fraught with the risk of intervening too late, thereby missing the opportunity of preventing the femoral head from getting deformed. The sequence of events described here is not seen if the onset of LCPD is in adolescence . Adolescent LCPD has a very poor prognosis as collapse of the epiphysis occurs early, revascularization and repair is often incomplete and permanent deformation is exceedingly common.