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 -- www.offa.org) 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, 11% 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, only 3,525 Cavaliers have been evaluated by OFA in the 24 years from 1982 through 2005. Considering that in 2005 alone, the AKC registered over 7,600 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 22% to 33% of all Cavaliers, or as many as one third 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.

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.