Legg–Calvé–Perthes disease (LCPD) is a childhood hip disorder initiated by a disruption of blood flow to the head of the femur. Due to the lack of blood flow, the bone dies (osteonecrosis or avascular necrosis) and stops growing. Over time, healing occurs by new blood vessels infiltrating the dead bone and removing the necrotic bone which leads to a loss of bone mass and a weakening of the femoral head.

The condition is most commonly found in children between the ages of 4 and 8, but it can occur in children between the ages of 2 and 15. It can produce a permanent deformity of the femoral head, which increases the risk of developing osteoarthritis in adults. Perthes is a form of osteochondritis which affects only the hip. Bilateral Perthes, which means both hips are affected, should always be investigated to rule out multiple epiphyseal dysplasia.