Risk Factors For Canine Hip Dysplasia

What are the risk factors for the development of hip dysplasia?

Hip dysplasia is caused by looseness in the hip joint. The looseness creates abnormal wear and erosion of the joint and as a result pain and arthritis develops. The disease process is fairly straightforward; the controversy starts when we try to determine what predisposes animals to contract the disease. Almost all researchers agree that there is a genetic link involved. If a parent has hip dysplasia, then the offspring are at greater risk for developing hip dysplasia. Some researchers feel that genetics are the only factor involved, where others feel that genetics contribute less than 25% to the development of the disease. The truth probably lies in the middle. If there are no carriers of hip dysplasia in a dog's lineage, then it will not contract the disease. If there are genetic carriers, then it may contract the disease. We can greatly reduce the incidence of hip dysplasia through selective breeding. We can also increase the incidence through selectively breeding. We cannot, however, completely reproduce the disease through selective breeding. In other words, if you breed two dysplastic dogs, the offspring are much more likely to develop the disease but will not all have the same level of symptoms or even necessarily show any symptoms. The offspring from these dogs will, however, be carriers and the disease may show up in their offspring in later generations. This is why it can be difficult to eradicate the disease from a breed or specific line.

Nutrition: Experimentally, we can increase the severity of the disease in genetically susceptible animals in a number of ways. One of them is through obesity. It stands to reason that carrying around extra weight will exacerbate degeneration of the joint in a dog with a loose hip. Overweight dogs are therefore at a much higher risk. Another factor that may increase the incidence is rapid growth in a puppy during the ages from three to ten months. Experimentally, the incidence has been increased in genetically susceptible dogs when they are given free choice high protein and high calorie diets. In a large study done in 1997, Labrador Retriever puppies fed a high protein, high calorie diet free choice for three years had a much higher incidence of hip dysplasia than their littermates who were fed the same high calorie, high protein diet but in an amount that was 25% less than that fed to the dysplastic group. As might be expected, however, the free choice group was significantly heavier at maturity and averaged 22 pounds heavier than the control group. Because obesity is also a risk factor, this study may be difficult to interpret.

We have yet to see a study that links an increased incidence of hip dysplasia in dogs fed a normal diet of commercial puppy food versus a specialty diet formulated for just large breed dogs.

There have also been studies looking into protein and calcium levels and their relationship to hip dysplasia. Both of these studies were able to increase the level of hip dysplasia by feeding increased amounts of calcium and protein. But once again, the studies of puppies fed greatly increased amounts over normal recommended values and compared them to animals fed decreased amounts. They failed to compare puppies fed a normal amount of food that had the recommended amount of protein, fat, and calcium to those fed a diet with slightly less protein, fat, and calcium (similar to those 'large breed puppy foods' that are now flooding the market). We have yet to see a study that links an increased incidence in hip dysplasia in dogs fed a normal diet of commercial puppy food versus a specialty diet formulated just for large breed puppies.

Exercise: Exercise may be another risk factor. It appears that dogs that are genetically susceptible to the disease may have an increased incidence of disease if they over-exercised at a young age. But at the same time, we know that dogs with large and prominent leg muscle mass are less likely to contract the disease than dogs with small muscle mass. So exercising and maintaining good muscle mass may actually decrease the incidence of the disease. Moderate exercise that strengthens the gluteal muscles, such as running and swimming, is probably a good idea. Whereas, activities that apply a lot of force to the joint are contraindicated. An example would be jumping activities such as playing Frisbee.