At what age does the average child with achondroplasia start to walk?
Head control is also delayed, and the majority of children with the condition are unable to hold their heads up independently until after seven months of age. Children with achondroplasia start to walk at approximately 18 months and at two and a half years old around 90 per cent of them can walk.The delay is the result of a combination of muscular weakness in the legs, hypermobility of the knee joints and an unusually large, heavy head, which is difficult to balance.f two people with achondroplasia have a child, there is a 25 per cent risk that the child will receive two copies of the mutated gene (a homozygote for this particular gene) causing significant skeletal abnormalities.