Hip Dysplasia in Cavaliers: Painful and Expensive
Hip Dysplasia (HD) is a common, heritable disease in Cavalier King Charles Spaniels which can cause the dogs terrible pain and debilitation. HD is the abnormal development of the hip, which can produce various degrees of arthritis (which also may be called degenerative joint disease, arthrosis, or osteoarthrosis).
Symptoms
It is not predictable as to when or even if a dog with HD will start showing signs of lameness due to pain. There are many environmental factors, including caloric intake and the level of exercise, which can affect the severity of pain and lameness. Many dysplastic dogs with severe HD can run, jump, and play as if nothing is wrong, and other dogs with barely any HD x-ray indications are severely lame.
Diagnosis
The only way to accurately diagnose HD is by radiography ( x-ray). The Orthopedic Foundation for Animals (OFA) provides x-ray evaluations by panels of board certified veterinary radiologists. The PennHip method of hip joint analysis is an alternative means of diagnosing HD, also by x-ray.
According to OFA's statistics, 12% of all Cavaliers are afflicted with hip dysplasia. However, the majority of Cavalier breeders do not submit to OFA any x-rays of their breeding stock which show obviously dysplastic hips. Therefore, OFA's statistics do not accurately reflect the incidence of HD in Cavaliers. For example, 4,754 Cavaliers have been evaluated by OFA in the 34 years from 1974 through 2008. Considering that in 2008 alone, the AKC registered over 8,000 Cavaliers, the OFA data base is woefully short. This indicates a major lack of interest by most all Cavalier breeders in obtaining objective, expert evaluations of their dogs' hips.
It is believed by specialists in the field of hip dysplasia that the true incidence of HD in the Cavalier King Charles Spaniel is two to three times as high as those statistics would indicate, meaning from 24% to 36% of all Cavaliers, or as many as one third or more of all of the dogs in the breed.
The PennHip method was developed in 1983 by Dr. Gail Smith, an orthopedic surgeon at the University of Pennsylvania School of Veterinary Medicine. It measures hip joint laxity (looseness), which is the primary cause of degenerative joint disease. The Distraction Index (DI) used in the PennHip method is a measurement of passive hip laxity, the degree of looseness of the hip joint when the dog's hips are completely relaxed. Dogs with a DI of 0.3 have tighter hips and are less likely to develop hip dysplasia, and dogs with looser hips and DI values approaching 0.7 or more are at greater risk.
Hip dysplasia is a developmental disease, meaning that it is not present at birth, but develops with age; it normally does not appear at all in x-rays of puppies or young Cavaliers. OFA requires that dogs be at least 24 months old when x-rayed in order to qualify for a permanent OFA evaluation. OFA evaluates the x-rays by assigning a classification to each dog, from excellent, good, fair, borderline, mild, moderate, to severe. Ideally, breeders should consider x-raying their breeding stock again annually thereafter, as hip dysplasia has been found to be a progressive genetic disorder which results in deterioration of the hip joints after age two years.
Treatment
Initial treatment is aimed at relieving pain and improving function with medication for the treatment of degenerative joint disease. If pain cannot be controlled there are expensive surgical procedures which may relieve pain and improve function in some dogs.
Breeders' Responsibilities
The Canine Inherited Disorders Database (www.upei.ca/~cidd/intro.htm) recommends that breeders breed only dogs that have disease-free joints and that come from ancestors with disease-free joints. The Canine Inherited Disorders Database further recommends not breeding any Cavaliers whose offspring have hip dysplasia (dogs with hip dysplasia can produce normal offspring, and normal-appearing dogs can produce offspring with hip dysplasia).
The general principles recommended by OFA for breeding away from HD are:
1) Breed only normal dogs (meaning, not dysplastic) to normal dogs.
2) The normal dogs should come from normal parents and grandparents.
3) The normal dogs should have over seventy-five percent normal siblings.
4) A dog with excellent hips from a litter having more than twenty-five percent dysplastic pups is a worse breeding choice than a dog with fair hips from a litter experiencing less than twenty-five percent dysplasia.
5) Choose replacement dams that have better hips than their parents and the breed average.
Breeders should have their breeding Cavaliers' hips x-rayed after age two years and have the x-rays evaluated by OFA before considering the dogs for breeding. Ideally, breeders should consider x-raying their breeding stock again annually thereafter, as hip dysplasia has been found to be a progressive genetic disorder which results in deterioration of the hip joints after age two years.
Related Links
Questions for Breeders
The Orthopedic Foundation for
Animals (OFA)
PennHip
Veterinary Resources
Control of Canine Genetic Diseases. Padgett, G.A., Howell Book House 1998, pp. 198-199, 245.
