Perthes Disease(Legg-Calve) 
Perthes disease (also known as Legg-Calve-Perthes disease, or Calve Perthes disease, or avascular necrosis) is a childhood disorder which affects the head of the femur ( the ball of the ball and socket joint of the hip). In Perthes disease the blood supply to the growth plate of the bone at the end of the femur (called the epiphysis) becomes inadequate. As a result the bone softens and breaks down (a process called necrosis).

It is not clear why this blood vessel problem occurs in the femoral head. It is not due to injury, or to a general blood vessel problem. A child with Perthes’ disease is usually otherwise well. Over several months the blood vessels regrow, and the blood supply returns to the ‘dead’ bone tissue. New bone tissue is then laid down and the femoral head regrows and remodels over several years. This is similar to how bone reforms and remodels after any ‘normal’ fracture or break to a bone, but takes longer.

Perthes disease is not really as a disease, but that was the name given to it when it was first discovered.