All puppies appear to be born with normal hips. In dogs affected with hip dysplasia, radiographic changes become evident within several months to several years. A good x-ray at a young age does not rule out the possibility of hip dysplasia occurring later in life. At 24 months, more than 95 percent of dogs with hip dysplasia show radiographic changes associated with the disease. The O.F.A. does not classify a dog's hips until he or she is at least two years old.