Avascular necrosis of the capital femoral epiphysis Osteonecrosis of the femoral head Avascular necrosis of the proximal epiphysis of the femur occurring in growing children and caused by an interruption of the blood supply to the head of the femur close to the hip joint. The necrosis is characteristically associated with flattening of the femoral head, for which reason the term coxa plana has been used to refer to this feature in the medical literature. Perthes-like femoral head changes Morbus Legg-Calve-Perthes In medical parlance, this is often referred to as Legg Calve Perthes disease. Here, the name 'Avascular necrosis of the capital femoral epiphysis' is preferred to emphasize that the term refers to a phenotypic feature rather than a disease entity. Avascular necrosis of the femoral head may result in pain in the hip, limp, stiffness and reduced range of motion, and some degree of atrophy of the affected leg. The phrase Legg Perthes syndrome or Legg Calve Perthes disease is also used to refer to a number of diseases, including the idiopathic form and a form that is related to mutation in the COL2A1 gene (MIM 150600). Legg-Calve-Perthes disease usually occurs in boys 4 to 10 years old, and is clinically characterized by limping, hip stiffness, limited range of motion, and can result in restriction of growth of the affected leg and wasting of the muscles of the upper thigh. Legg-Perthes disease HP:0010887 HP:0006448 SNOMEDCT_US:111255008 Legg-Calve-Perthes syndrome HP:0005743 Osteochondrosis of the femoral head SNOMEDCT_US:240241003 ICD-10:M91.1 Coxa plana UMLS:C0023234 HP:0003280 Abnormality of the epiphysis of the femoral head Juvenile aseptic necrosis