This requires sedation of some sort and many vets will use a general anesthesia before they take the x-ray. OFA has very explicit instructions for the positioning of the dog for the x-ray. OFA is not the only choice for hip certification. PennHIP certifies vets as to the positioning of the dog and claims accuracy for dogs as young as 16 weeks. There is some controversy surrounding the importance of passive hip laxity.
Some researchers claim that the relationship between hip laxity and hip dysplasia is tenuous.
A closed registry certifies dogs that have hips that have been determined to be free of CHD but releases no information about dogs that failed or other dogs that might be related. Open registries, on the other hand, provide full disclosure of a dog's status and also of all of its kin in the registry. Although OFA and PennHIP have had an impact on reducing the incidence of CHD, more could be gained with an open registry. The GDC came about when the breeders of Bernese Mountain Dogs wanted to establish an open registry to help control elbow dysplasia in their breed. None of the existing registries were interested in having an open registry and in 1990 GDC was formed to be an open registry for elbow dysplasia, CHD, and a number of other hereditary diseases.