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What is Perthes disease?

What is Perthes disease?

Perthes disease is a childhood disorder which affects the top of the femur bone. The femur is the bone in your thigh. It affects the ball part of the ball and socket joint where it meets the hip. In Perthes disease, the blood supply to the top of femur is reduced, making the bone soften and break down. This is known as ‘avascular necrosis’.

This causes the ball of the joint to be flattened, rather than round. This reduces the movement of the hip joint. There are 4 stages to the disease with the end stage being remodelling. This whole process can take between 2 to 4 years.

What is the cause of Perthes disease?

The cause is unknown. It is more likely to happen in boys than girls and most commonly occurs between 4 and 8 year olds.

Signs and symptoms

Signs and symptoms of Perthes disease include:

  • Persistent hip or groin pain, however knee pain may be the only symptom
  • A painful limp may be present
  • Wasting of the muscles in the upper thigh and bottom
  • Loss of movement at the hip, with stiffness and muscle spasms
  • Sometimes shortening of the affected leg

What may my child need?

Your GP may refer your child for an X-ray of the hip, which can diagnose the presence of Perthes disease.

How do I help my child?

Your child should avoid heavy impact on the joint such as running or jumping activities. Encourage swimming and other non-weight bearing activities to help keep your child fit.

Physiotherapists can give exercises to help maintain a full range of motion. Support your child with their physiotherapy.

As your child’s physical activity will be restricted you may need to consider a more healthy diet.


Abduction and adduction

Ask your child to lie on their back, and bring their leg out to the side and then back across the mid position. Repeat 10 times, 3 times a day.

Photograph of person laid on their back with another person stretching out their legPhotograph of person laid on their back while someone else stretches out their leg

Flexion and extension

Ask your child to lie on their back, bend their knee towards their chest and then lower back down to the surface.

Person laid on their back with someone lifting their leg to bend at the knee and stretch the thigh

Ask your child to lie on their tummy, bend their knee and then lift their foot towards the ceiling. Repeat 10 times 3 times a day.

Photograph of person laid on their front with someone else raising their leg and bending at the knee to stretch the thigh

External rotation and internal rotation

Ask your child to lie on their tummy with their knees bent to 90 degrees. Keeping the knees together, take their feet away from each other and then towards each other, just like windscreen wipers. Repeat 10 times 3 times a day.

Photograph of person laid on their front with someone else crossing legs to stretch them outPhotograph of person laid on their front with someone else parting their legs at the knee

The amount of activity your child will be allowed to do will depend on the severity of the condition and the specialist doctor will guide you with this. Please remember that your child’s own specialist is the person to ask about the activities which they feel appropriate for your child.

Treatments advised will depend on the age of your child and the severity of the condition. Treatments may include ‘observation’, crutches, surgery, and short term hospital rest.

It is now known that at least half of cases heal well without any treatment, particularly children aged 5 and under, and milder cases.

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Please note this is a generic information sheet relating to care at Sheffield Children’s. The details in this resource may not necessarily reflect treatment at other hospitals. This information is not intended as a substitute for professional medical care. Always follow your healthcare professionals’ instructions. If this resource relates to medicines, please read it alongside the medicine manufacturer’s patient information leaflet. If you have specific questions about how this resource relates to your child, please ask your doctor.

Resource number: PT20

Resource Type: Article

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