The majority of cases affect one hip; 10 to 12 percent of cases affect both hips, but not usually at the same time.The condition is rare—affecting about one in every 12,000 children. Of these, 99.8% are normal and only 0.2% are abnormal. ). We found a delay in bone age; mean of 28 months in children 6 to 10-years-old, mean of 8 months in children 10 years and older by quadratic regression. Previous series report patients with LCPD delayed bone age of 22 months.