Hip X-Rays are used to diagnose traumatic injuries, soft tissue swelling and other potential causes of hip lameness.
There are several accepted versions of canine hip x-rays which are used by breed associations and registered breeders.
OFA Hip X-Ray test
One of the accepted diagnostic tests for canine hip dysplasia is an x-ray test offered by the Orthopedic Foundation for Animals - OFA. The OFA Hip X-Ray test uses a single "hip-extended view" x-ray to determine laxity of the hip joint (a predictive measure of the likelihood of developing hip dysplasia). In general, dogs with excellent and good OFA grades are approved for breeding. According to the OFA, "A responsible puppy buyer only purchases dogs from those breeders that certify hips/elbows of the parents and provides guarantees for hips & elbows."
PennHIP X-Ray test
The PennHIP X-Ray was created by veterinarians at the University of Pennsylvania Veterinary School. Along with the OFA Hip X-Ray, it is one of the recognized diagnostic procedures for screening hip dysplasia.
The PennHIP X-Ray is said to be more accurate than the OFA Hip X-Ray in predicting the onset of osteoarthritis. This is because the PennHIP X-Ray test uses 3 radiographic views (the distraction view, the compression view and the hip-extended view) to determine laxity of the hip joint (a predictive measure of the likelihood of developing hip dysplasia). In contrast, the OFA test uses a single x-ray.