To this day, the cause of Perthes disease remains unclear.  A great review article available publicly on https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6429000/ summarizes prior research studies identifying potential causes and associations with Perthes disease.

The article concisely summarizes previously studied associations including various exposures, genetic factors, and socioeconomic factors.

There certainly is need for more research on the cause of Perthes disease to find a cure.