Understanding Perthes disease

It is just over a century since Perthes disease (also known as coxa plana, Legg-Calvé-Perthes, Legg-Perthes, and/or Legg-Calvé), a disease that affects the hips in children, was first identified. It remains extremely rare, and indeed it is growing rarer. Many practitioners do not register that this may be why children are in considerable pain and/or have difficulty walking, sometimes for years. Indeed, even when children are diagnosed, they may receive any one of a whole number of treatments.

The disease pattern is still not fully understood; but, very broadly, there seem to be environmental rather than genetic factors involved. It mainly affects boys (around 80% of cases). Worldwide, studies to date show that the greatest incidence is in northern Europe, with the incidence rising sharply by around nearly 50% with every 10 degrees further north from the equator. In the UK, it is much more prevalent in the northern regions.

There also appears to be a familial but not a genetic element involved: research on twins showed that if one twin has the disease, the chance of the other twin being affected is no higher in identical twins compared to non-identical twins, but there is a slightly higher likelihood that a family member will be affected compared to the normal population (Metcalfe et al, 2016). There is also a link with social deprivation, with deprived children being much more likely to develop it (Perry et al, 2012).