The phenotypic evaluation of hips done by the Orthopedic Foundation for Animals falls into seven different categories. Those categories are normal (Excellent, Good, Fair), Borderline, and dysplastic (Mild, Moderate, Severe). Once each of the radiologists classifies the hip into one of the 7 phenotypes above, the final hip grade is decided by a consensus of the 3 independent outside evaluations. Examples would be:

1. Two radiologists reported excellent, one good—the final grade would be excellent
2. One radiologist reported excellent, one good, one fair—the final grade would be good
3. One radiologist reported fair, two radiologists reported mild—the final grade would be mild

The hip grades of excellent, good and fair are within normal limits and are given OFA numbers. This information is accepted by AKC on dogs with permanent identification (tattoo, microchip) and is in the public domain. Radiographs of borderline, mild, moderate and severely dysplastic hip grades are reviewed by the OFA radiologist and a radiographic report is generated documenting the abnormal radiographic findings. Unless the owner has chosen the open database, dysplastic hip grades are not in the public domain.

Excellent (Figure 1): this classification is assigned for superior conformation in comparison to other animals of the same age and breed. There is a deep seated ball (femoral head) which fits tightly into a well-formed socket (acetabulum) with minimal joint space. There is almost complete coverage of the socket over the ball.

Good (Figure 2): slightly less than superior but a well-formed congruent hip joint is visualized. The ball fits well into the socket and good coverage is present.

Fair (Figure 3): Assigned where minor irregularities in the hip joint exist. The hip joint is wider than a good hip phenotype. This is due to the ball slightly slipping out of the socket causing a minor degree of joint incongruency. There may also be slight inward deviation of the weight-bearing surface of the socket (dorsal acetabular rim) causing the socket to appear slightly shallow (Figure 4). This can be a normal finding in some breeds however, such as the Chinese Shar Pei, Chow Chow, and Poodle.

Mild Canine Hip Dysplasia (Figure 5): there is significant subluxation present where the ball is partially out of the socket causing an incongruent increased joint space. The socket is usually shallow only partially covering the ball. There are usually no arthritic changes present with this classification and if the dog is young (24 to 30 months of age), there is an option to resubmit an radiograph when the dog is older so it can be reevaluated a second time. Most dogs will remain dysplastic showing progression of the disease with early arthritic changes. Since HD is a chronic, progressive disease, the older the dog, the more accurate the diagnosis of HD (or lack of HD).