Perthes' disease

Perthes' disease is a condition of the hip joint that tends to affect children between the ages of 3 and 11 years.

The top end of the thigh bone (femur) is shaped like a ball so that it can fit snugly into the hip socket. In the case of Perthes' disease, this ball (femoral head) is softened and eventually damaged due to an inadequate blood supply to the bone cells. Boys are more likely to develop Perthes’s disease than girls. In most cases only one hip joint is affected.

Most children with Perthes' disease eventually recover, but it can take anywhere from 2 to 5 years for the femoral head to regrow and return to normal, or close to normal.

Perthes' disease is also known as Legg-Calve-Perthes disease or coxa plana.

Symptoms of Perthes' disease

The symptoms of Perthes' disease include:

• an occasional limp in the earlier stages
• stiffness and reduced range of movement in the hip joint
• pain in the knee, thigh or groin when putting weight on the affected leg or moving the hip joint
• thinner thigh muscles on the affected leg
• shortening of the affected leg, leading to uneven leg length
• worsening pain and limping as time goes by.

The cause of Perthes' disease is unknown

Your bones needs a regular supply of blood to stay healthy. Blood provides your bones with oxygen and other nutrients. In children with Perthes’ disease blood supply to the femoral head is disrupted. It is not known what causes this to occur. Without enough oxygen and nutrients, the bone cells of the femoral head die.

Diagnosing Perthes' disease

Your doctor will do a number of examinations and tests to work out what’s causing your child's symptoms. These will include:

• medical history – to get a better understanding of the situation your doctor will ask you when you first noticed the symptoms, what makes the symptoms worse, what makes them better, if there are any other health issues
• your doctor will also conduct a physical exam, which will involve moving your child's legs through their range of movement. This will help identify any positions that cause pain or stiffness.

Other tests may also be required and include:

• x-rays
• magnetic resonance imaging (MRI)
• bone scan
• ultrasound
• blood tests (to rule out infection).

These will give your doctor a picture of what’s happening inside your child's joints.

Treating Perthes' disease

In most cases, the blood supply to the hip joint returns and the femoral head regenerates by itself. This can take anywhere between 2 and 5 years. During this critical period, the bone is soft and vulnerable to damage.

Treatment of Perthes' disease aims to make sure the femoral head remains as round as possible, and to reduce joint pain and stiffness. Treatment depends on your child's age and the severity of their condition, but may include:

• regular monitoring by your doctor, including physical examinations and x-rays
• pain medication
• physiotherapy to help keep the hip joint moving and to help maintain muscle strength
• avoidance of high impact activities such as running and jumping
• a brace, splint or plaster – may be used if your child’s range of movement in the hip is affected, or if x-rays show that the femoral head is losing its rounded shape
• short term bed rest – may be required when the pain is especially bad
• rest – your doctor may advise rest using crutches, a walker or a wheelchair for a period of time
• surgery –some children require surgery to treat the deformed femoral head so that it fits snugly within the hip socket.

Long-term outlook for Perthes' disease

In most children, the blood supply to the hip joint returns and the femoral head regenerates by itself. During this time, support your child to find other activities they can enjoy that don’t require weight bearing on the affected leg.

Generally speaking, the younger the child is when they develop Perthes’ disease, the better the outcome. The degree of damage to the femoral head also determines the long-term outlook. Some children may develop osteoarthritis in the affected joint later in life, and in rare cases, hip replacement surgery may be required.

However most children respond well to treatment and are able to get back to their usual activities.

Where to get help

• Your GP (doctor)
• Physiotherapist
• Orthopaedic surgeon
• Musculoskeletal Australia National Help Line Tel. 1800 263 265