To investigate the developmental pattern of femoral shortening in Legg-Calve-Perthes disease, the authors made an experimental model of the disease in piglets by devascularizing the capital femoral epiphysis and following the piglets to skeletal maturity. The discrepancy first increased in the postoperative 0 to 8 weeks (1.2-1.9 mm of shortening per week), then decelerated for a considerable period during the postoperative 8 to 16 weeks (0.2-0.6 mm per week), and then increased again toward the end of the growth period of the postoperative 20 weeks (1.2 mm per week). The developmental pattern of femoral shortening showed an upward slope/plateau/upward slope pattern, as in type IV of the Shapiro classification. As the mechanism of the observed pattern, the authors presumed reduced epiphyseal height and growth retardation in the physis during the initial upward slope, a repair process at the plateau phase, and premature physeal closure during the second upward slope.