What is Perthes disease?

Perthes disease is a condition that affects the hip joint in children. One, or more rarely, both joints are involved. The condition causes pain in the hip and typically presents with a limp. The hip joint is a ball and socket type joint, the femoral head is the ball and the pelvis forms the socket around it. The normal hip joint is both strong and flexible with a wide range of movement.

The underlying problem in this condition is disruption of the blood supply to the femoral head – the ball of the socket. Areas of the femoral head lose their blood supply and these areas of bone die. The medical term for this process is avascular necrosis. The process of bone death and subsequent healing causes inflammation in the joint. Active inflammation is painful and walking exacerbates this.

Picture shows Perthes disease – note the flattened appearance on the affected side, compared to the smooth curve of the femoral head on the normal side.

Reproduced with the kind permission of Dr Nuno Craveiro Lopes. Hospital Garcia de Orta, Almada, Portugal.

The dead areas of bone heal over time. In a mild case a small area of bone is affected and it heals over time by itself with little change to the shape of the femoral head. In a more severe case larger areas of the femoral head are affected and the bone can become soft. Ordinary weight bearing can lead to crushing of areas of the femoral head. Without treatment the healing process leads to flattening and deformity of the femoral head. This means the ball and socket joint does not work smoothly and the range of movement is reduced. Although the bone heals over several years the deformed flattened femoral head leads to early onset arthritis of the affected hip.

The aim of treatment is to prevent deformity from developing whilst the femoral head heals. Treatment will vary depending on how much of the femoral head is involved. Activities that could damage the softened bone such as running and jumping on hard surfaces may be restricted. In mild cases bed rest and crutches may be needed during periods when the hip is too painful to allow full weight bearing. In more severe cases surgical treatment, immobilisation of the joint in plaster or wearing a brace may be necessary.

This condition has a variable effect on mobility, typically for 2-4 years until healing has occurred. Mobility is likely to be maintained in mild cases that are being treated with physiotherapy, painkillers and x-ray monitoring. Those undergoing active treatment with surgery, immobilisation in plaster or bracing are most likely to be unable to walk for a prolonged period. Once the condition has resolved mobility returns to normal and joint mobility usually returns to give a functional range of movement even if the hip joint is abnormal. In the longer term arthritis of the hip can develop at a young age, typically around 40 years.

Incidence/prevalence

Perthes Disease (also called Legg-Calve-Perthes Disease) is a disease of childhood. It affects children aged between 3 and 10 years, with a peak between 5 and 7 years. It is four times more common in boys than girls. In most cases one hip is affected, in one in ten cases both hips are affected. It affects 10 -15 per 100 000 each year.