Perthes disease is a painful condition of the hip that affects children.

It takes time, but most children recover fully.

What is Perthes disease?

Perthes disease is a problem with the blood supply to the top of the thighbone, or femur. The top of the femur is a ball, sometimes called the femoral head.

The femoral head fits into a socket in the pelvis to form the hip joint. It is called a ball and socket joint.

In Perthes disease, the femoral head becomes soft and goes out of shape. This causes pain and a limp.

Causes of Perthes disease

It is not clear why the blood supply to the femoral head is reduced.

Perthes disease usually affects children aged from 3 to 11 in one hip. In some cases, it affects both hips, and it sometimes runs in families. It is more common in boys than in girls.

Symptoms of Perthes disease

Symptoms of Perthes disease include:

• pain in the hip, knee, thigh or groin
• a slight limp that becomes worse over time
• limited movement
• uneven leg length — the affected leg may become shorter

Children with Perthes disease are otherwise healthy.

Diagnosis of Perthes disease

If your child has pain in the hip, your doctor may suggest an x-ray to diagnose Perthes disease. If the x-ray doesn’t provide an answer, other more sensitive tests can include:

• MRI scan
• ultrasound
• bone scan

Treatment of Perthes disease

If your child has Perthes disease, he or she will probably be referred to a specialist.

The bone will repair itself, as long as it is not too damaged. This takes time, usually between 2 and 5 years.

The aim of treatment is to avoid making it worse. This might include:

• avoiding activities with a high impact on the hip, such as running
• rest and use of a wheelchair or crutches
• a splint or a plaster
• special exercises

A few children will need surgery.