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.

In some cases, some activity can cause severe irritation or inflammation of the damaged area, including standing, walking, running, kneeling, or stooping repeatedly for an extended period.

[3] Perthes disease 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.

Currently, a number of factors have been implicated, including heredity, trauma, endocrine dysfunction, inflammation, nutrition, and altered circulatory hemodynamics.

Symptoms like femoral head disfigurement, flattening, and collapse occur typically between ages four and ten, mostly male children of Caucasian descent.

Children affected by LCP disease often display uneven gait and limited range of motion, and they experience mild to severe pain in the groin area.

[9] The bone loss leads to some degree of collapse and deformity of the femoral head and sometimes secondary changes to the shape of the hip socket.

Perthes can produce a permanent deformity of the femoral head, which increases the risk of developing osteoarthritis in adults.

Usually, plain radiographic changes are delayed six weeks or more from clinical onset, so bone scintigraphy and MRI are done for early diagnosis.

Many children, especially those with the onset of the disease before age 6, need no intervention at all and are simply asked to refrain from contact sports or games which impact the hip.

Current treatment options for older children over age 8 include prolonged periods without weight bearing, osteotomy (femoral, pelvic, or shelf), and the hip distraction method using an external fixator which relieves the hip from carrying the body's weight.

Swimming is highly recommended, as it allows exercise of the hip muscles with full range of motion while reducing the stress to a minimum.

Physiotherapy generally involves a series of daily exercises, with weekly meetings with a physiotherapist to monitor progress.

Performing these exercises during the healing process is essential to ensure that the femur and hip socket have a perfectly smooth interface.

[18] Children younger than six have the best prognosis, since they have time for the dead bone to revascularize and remodel, with a good chance that the femoral head will recover and remain spherical after resolution of the disease.

[19] Children who have been diagnosed with Perthes' disease after the age of ten are at a very high risk of developing osteoarthritis and coxa magna.

[6] White northern Europeans appear to be affected more frequently than other ethnicities, though a paucity of reliable epidemiology exists in the Southern Hemisphere.

[21] Children of those with the disease themselves may have a very slightly increased risk, though it is unclear if this is because of a genetic predisposition, or a shared environmental factor.

[36] Every hospital in England, Scotland, and Wales which treated Perthes' disease collected details of new cases, with the BOSS study demonstrating the major variation in treatment across the UK, with no clear benefit of surgery over non-surgical care.

[39] The pathology of avascular necrosis followed by revascularization and bony remodeling of the femoral head in the dog certainly suggests a vascular etiology, though the cause of the condition is not completely understood.