Hip dysplasia is a polygenic disease, which means it takes more than 1 gene to produce it. A dogs head structure is also polygenic. Many genes are responsible in making the structure of a head (ex. length of muzzle, stop, lip, planes). Many breeders state they are going to "fix" their heads by breeding to a dog or bitch that has the more desirable traits, when in fact this is not an easy fix and usually requires a few generations to correct. Hip dysplasia sits in the same category. The theory is to "fix" hips by breeding up. Hip dysplasia is one of the most misunderstood defects purebred dog breeders face today. The following is reproduced from an article in the AKC gazette, July 2002, Vol. 119, NO 7 authored by Jerold S. Bell, DVM. "The OFA evaluates the hip radiograph for nine anatomical aspects. These include a round femoral head, a deep acetabulum, a prominent notch in the femoral neck, a straight up and down cranial rim of the acetabulum, and minimal joint laxity. The British Veterinary Association/Kennel Club (BVA/KC) evaluates the same extended-leg radiograph at 1 year of age or older. Unlike OFA's rating system, it separately scores the nine anatomical aspects of the pelvic radiograph for each hip. The nine scores are added up for each hip, then totaled for the dogs final rating. Since hip dysplasia is a polygenic disorder controlled by several gene pairs, the disease affects individual dogs due to different genetic combinations. One reason selection offers limited results is that many breeders are selecting dogs based solely on their OFA hip rating, and not on the specific aspects of the hip radiograph. If a dog's hips have demonstratable laxity, then it should be bred to a dog with tight hips. The BVA/KC's dysplasia rating information allows breeders to identify precisely how their dog's hip-rating points are calculated. With this system, it is easier to select prospective mates that will correct and compliment the different elements of hip joint conformation. With the OFA system, it is up to the individual breeder to work with their veterinarian to break down the hip radiograph into these separate components. By selecting for individual components of the hip radiograph, you may be more directly selecting for specific "normal hip" genes. The most important factor in selecting against a polygenic disorder like hip dysplasia is to seek breadth of pedigree. Most breeders select normal parents with normal grandparents, and expect to produce all normal offspring. This is selection based on depth of pedigree. With polygenic traits, the hip status of breeding dogs' siblings beter represents the range of genes that can be present. With breadth of normality in the littermates of breeding dogs, and even of parents of breeding dogs, you are more efficiently selecting for a preponderance of those "normal-hip" genes." Many veterinarians feel there is no such thing as unilateral (only affecting 1 side) hip dysplasia, since it is a disease associated with collagen synthesis. Inadequate collagen synthesis will adversely affect development and formation of bone, cartilage, and muscle, thereby affecting both hip joints.We will be applying these thoughts with Tsunami. She was diagnosed with mild sublaxation to her left hip only, with no remodeling of femoral head, and no other changes to the 9 points noted. Her right hip was graded "good" taking into account the 9 points. Tsunami may be a quite common case. She sustained an injury to that hip at a younger age, and also had a severe case of parvo as a puppy. With a disease process such as parvo with the large protein loss, this may have also contributed to her rating. All her littermates are hip dysplasia free. We have utilized the "breed up" with Typhoon, who scored a "good" on OFA radiograph readings. Would we breed her if she had mild or worse hip dysplasia to both hips without her background, "No." This is something breeders need to apply also. If we feel we can "fix" heads, shoulders, toplines ect...then we should and can also test-mate for hips to document if it is true hip dysplasia.