From 1974 to 2005, we treated 520 hips in 471 patients with developmental dysplasia of the hip (DDH). Among these, 101 hips in 89 patients (18.9%) were diagnosed as DDH when they were older than six months. In addition, 43 patients were diagnosed after they had begun to walk. In the 1970’s the rate of DDH diagnosis after six-month-old patients was 30.3%. From the 1980’s to the 1990’s this rate decreased, but increased again to 24.3% after 2000. We compared gender, family history of DDH, affected side and treatment method (conservative treatment or operation) between patients diagnosed before six months old and after six months old. No significant differences were found except for treatment method. 22.4% of DDH patients diagnosed before six months old were treated by surgery, compared to 69.3% of patients diagnosed older than 6 months. In conclusion it became clear that the rate of DDH diagnosis at an older age has increased in recent years, so we argue that it is important to improve the accuracy of the medical examination for DDH.
