Discussion on Hip Dysplasia

The primary genetic diseases currently thought to be a problem in the breed are as follows: Hip Dysplasia (HD) HD is by far the most prevalent known genetic disease that affects Border Collies. Factors that contribute to the development of HD ultimately cause the hip joint to be damaged. Joint damage called osteoarthritis, also known as degenerative joint disease (DJD) is manifested by cartilage and bone breakdown and irregular bony remodeling in response to stresses and inflammatory processes in the joint. DJD is, in effect, the identifiable result of factors that cause HD.

The standard for diagnosing HD at this time is still the front extended-leg view of the hips on x-ray such as that evaluated by The Orthopedic Foundation for Animals (OFA). OFA reports a 12.6% affected rate for Border Collies evaluated from 1974-2000. This HD incidence ranks them somewhere in the middle of the dog breeds. Pre-submission screening and selection for probable favorable OFA results by owners and their veterinarians very likely skews this percentage significantly to the low side. Therefore, the true incidence of HD is probably much higher, possibly as high as double the OFA figure. If true, this would mean, on average, one out of every four Border Collies has HD.

Despite what some may claim, data from numerous scientific studies provide overwhelming evidence that HD is an inherited disease. It is thought to be caused by at least three and possibly as many as six primary genes. The number of genes involved, combined with the high incidence, means it’s probable that most Border Collies are at least carriers of one or more of the genes that can contribute to the development of HD, even if they don’t have the disease themselves. To confuse matters more, the expression of the disease is affected by environmental conditions such as the type and amount of food a dog gets at critical growth stages, as well as the type and amount of exercise and activity it gets. It must be remembered, however, that these environmental factors do not cause HD. They merely affect whether the HD genes present in that individual will be expressed to the fullest. Even if the expression of HD in a certain individual is suppressed by careful control of environmental factors, you have not changed the dog’s genetic makeup. That dog will still pass on the genetic tendency for HD just as if it actually had the disease. Conversely, if a dog does not have the genes for HD, it won’t develop the disease no matter how it’s raised.

The possible incidence of one in four dogs may seem falsely high if the presence of HD is defined by dogs showing significant lameness.  The clinical symptoms of HD do not always correlate well with the severity of the disease as judged by radiological findings. Border Collies with HD that are fortunate enough to show few if any symptoms may have progeny that are not so fortunate.  The exact complex combination of genetic and environmental factors that contributed to an individual’s lack of symptoms will not occur in its pups.  Therefore, it is important to remember that a high tolerance of an individual for the effects of HD does not mean that individual is suitable as a breeding prospect.

 The best way, at this time, to avoid producing puppies with a predisposition to develop HD is to test both parents and be aware of the hip status of other related dogs such as the parents’ other progeny, the parents’ parents, and the littermates and half siblings of the parents. The more tested, unaffected dogs there are in the pedigrees, the better the chances of producing unaffected pups. Unfortunately, even following the most stringent guidelines, puppies may still be produced that will develop HD. This does not mean there’s no point in testing parents before breeding them. This line of false reasoning is akin to arguing that, because working parents will occasionally produce pups that won’t work, there’s no point in testing the working ability of breeding stock.

Selection for good hips will increase your chances of producing pups with good hips, but it’s unrealistic to expect that puppies with HD will never be produced from tested, unaffected parents. Likewise, it is unrealistic to expect every dog who has ever produced a pup with HD to be banned from breeding. Since it’s likely that most non HD-affected Border Collies are carriers of one or more of the genes for HD, most dogs will produce at least one pup with HD if bred enough times. Sooner or later, a cross with another carrier will produce the wrong combination of the HD genes and an affected pup will result. Given the incidence and complexities involved with HD in our breed, the recommendations at this time are to breed only hip tested, unaffected parents. Also, try to plan crosses having as many tested, unaffected dogs in the pedigrees of both parents as possible. If an affected puppy is produced from a cross of two unaffected parents, at the very least, don’t repeat that particular cross because that affected puppy has proven that the two parents can together provide the right combinations of genes to create more puppies with HD.

The ABCA Health and Genetics Committee is investigating a promising new technique that measures several factors involved in the development of HD. This procedure involves taking hip x-rays on a sedated dog while the dog is in a kneeling position. This angle is favorable for identifying strengths and weaknesses in the hip joint in a more natural, weight-bearing position. This type of measurement is called a Dorsolateral Subluxation (DLS) measurement. ABCA is planning a study to evaluate this technique in 8-12 month old Border Collies.