Perthes Disease

This is a childhood condition of the hip joint usually presenting at the age of between 4 and 8 years of age. It is 3 times commoner in boys than girls and affects about 1 in every 10,000 children. There are hotbeds of the disease in the UK where the incidence is higher than this and the disease more severe. South Wales is unfortunately one of these areas as well as Merseyside and Northern Ireland. In 10% of cases it can affect both hips at different times.

The cause of the disease is unknown, although there are a number of theories ranging from injury to blood disorders. There may be a genetic tendency to developing the disease, although this again is unproven.

The clinical symptoms of the disease are usually a painful limp which develops with no obvious cause. Some children present with just knee pain on the affected side as hip pain can sometimes be felt purely in the knee. This is known as referred pain.

The cause of the painful limp is that the hip temporarily loses its blood supply and over a prolonged period, the femoral head (ball part of the hip) starts to soften and collapse (fig 1). This causes inflammation in the hip. With time it recovers its blood supply and heals, but all too frequently it does not grow back perfectly round and can become an ovoid shape. The worst possible long term consequence of the disease is therefore premature osteoarthritis of the hip as the hip becomes more like a roller-bearing joint than a normal ball and socket joint (fig 2).

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