"Canine hip dysplasia is one of the most baffling diseases afflicting dogs today," said George Lust, Ph.D., the Cornell professor of physiological chemistry who organized the symposium and who has studied the disorder for more than 25 years. "We know this is an inherited disease, but identifying the so-called 'hip dysplasia gene' is proving difficult because this seems to be a polygenic disorder, with several different genes responsible. Furthermore, these may be 'masked' or hidden genes that are not expressed in several generations until the disease turns up again in the progeny. That's why there is such a low level of confidence when breeders say: 'There is no background of hip dysplasia in my dogs' lines.' "

Conscientious dog breeders are anxious for a genetic screening procedure that would help eliminate hip dysplasia in future generations, and that is one of the topics set for discussion at the international symposium. Among other topics are improved radiographic techniques to diagnose hip dysplasia earlier in a dog's life; nutrition, including evidence that hip dysplasia can be delayed or prevented altogether when the growth rate of susceptible puppies is restricted; and the effect of maternal hormones, such as estrogen and relaxin.

Proceedings of the symposium's scientific session will be published in a special issue of the Journal of the American Veterinary Medical Association (JAVMA). The hip dysplasia symposium is one in a series of scientific conferences presented by the Baker Institute for veterinary and biomedical researchers, veterinary practitioners and animal breeders. A leader in canine studies for almost 50 years, the James A. Baker Institute for Animal Health aims to improve the health of animals through basic and applied research.

Five misconceptions about canine hip dysplasia
(From the John M. Olin Laboratory for the Study of Canine Bone and Joint Diseases
James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University)

-- Only hip joints and surrounding tissues are affected. Rather, evidence now indicates that the shoulder and knee joints and some intervertebral joints may show similar changes: the loss of cartilage, inflammation of the joint capsule, bone damage and the growth of spurs at the bone-cartilage interface. Hip dysplasia is simply the most conspicuous -- and most painful -- manifestation of this form of osteoarthritis.

-- Only dogs suffer hip dysplasia. While 50 percent of some of the larger dog breeds are afflicted, the disease is not unknown in humans. About 1 percent of the general human population suffers hip dysplasia, and the rate for the inherited disease is higher in some populations of American Indians. Many Navajos in New Mexico went through life with hip dysplasia until mothers stopped the traditional practice of strapping infants, straight-legged, to cradle boards and allowed babies to assume the more relaxed, bent-legged position. Replacement of diseased hip joints with artificial joints is one treatment, both for canine and human patients.

-- The absence of hip dysplasia in canine parents guarantees dysplasia-free pups. Unfortunately, out of 100 matings of "normal" dogs in breeds affected by hip dysplasia, 75 percent of puppies will be "normal" but 25 percent, on average, will have hip dysplasia. Genes for hip dysplasia are believed to be "masked" or hidden in some generations, making the elimination of the disease from breeding stock even more difficult. Canine hip dysplasia was first diagnosed in the 1930s, but probably has troubled domestic and wild canines for centuries.

-- All large-sized breeds of purebred dogs are candidates for hip dysplasia. Although the disease is particularly common among certain large breeds (from Bernese Mountain Dogs, Bloodhounds and Boxers to Rottweilers, St. Bernards and Welsh Corgis) mixed breeds of all sizes also are subject to hip dysplasia and not even the toy breeds are spared. However, the incidence is lower in small dogs. Large-sized breeds with a relatively low incidence of hip dysplasia include the Borzoi, Doberman Pinscher, Great Dane, Greyhound, Irish Wolfhound and Siberian Husky.

-- A hearty diet helps avert hip dysplasia. To the contrary, dogs that are genetically predisposed to hip dysplasia seem to benefit from a lean diet during their first two years. In one study beginning at eight weeks of age, pups that were restricted to a 24-percent smaller ration had a 46-percent lower occurrence of hip dysplasia than pups that could eat freely. Slowing the growth rate during the early months of life, some veterinary nutritionists now believe, can lessen the severity of hip dysplasia and even prevent it.

Credit for this article to Prof Salman Mo - Colorado University [email protected]