Hip dysplasia

What is ... ?: 

The hip joint is a "ball and socket" joint: the "ball" (the top part of the thigh bone or femur) fits into a "socket" formed by the pelvis. If there is a loose fit between these bones, and the ligaments which help to hold them together are loose, the ball may slide part way out of the socket (subluxate). With time, as this occurs repeatedly, other degenerative changes in the joint occur (also called osteoarthritis) and your dog will become painful, lame and weak in the hind end.
This disease is progressive; that is, it gets worse with time.

How is ... inherited?: 

The mode of inheritance of this disease is polygenic (caused by many different genes). Scientists do not yet know which genes are involved, or how many genes. Factors that can make the disease worse include excess weight, a fast growth rate, and high-calorie or supplemented diets.

What does ... mean to your dog & you?: 

While there is a severe form of hip dysplasia that affects young dogs (less than one year of age), signs of this disease are most common in older dogs. The loose fit at the hip joint will be present in young dogs, but it may take years for the other changes (such as osteoarthritis) to cause pain. Your dog may be painful after exercise, have difficulty with stairs, or even have difficulty getting up. You may only notice this once in a while, but over time you will find it getting worse. There is no cure, but your dog’s pain and lameness may be reduced by making sure that s/he is not overweight, restricting exercise, and using pain-relieving medications and/or alternative therapies such as acupuncture.
Large and giant-breed dogs are more likely to get hip dysplasia later in life if they are overfed and gain weight quickly as puppies. If you have such a puppy, you may be able to reduce the chance of future hip dysplasia by careful feeding. Your veterinarian can help you determine the right body weight and diet for your dog.

How is ... diagnosed?: 

Your veterinarian will probably suspect hip dysplasia if your large or giant breed dog has pain or lameness in the hips. Your vet will take x-rays to evaluate the general fit of the femur and pelvis, and to look for any osteoarthritic changes in the hip joint. Usually sedation or anaesthesia is required to ensure proper positioning of the dog.  In order to see how much looseness there is in the hip joint, your veterinarian may take special stress or distraction radiographs.

How is ... treated?: 

The degree to which the hips are dysplastic does not always correlate with the amount of pain. Some dogs with very bad hips radiographically are less painful than others whose x-rays show only minor changes.
Although there is no cure for hip dysplasia, there are ways to manage the pain. Your veterinarian will  work with you to keep your dog comfortable. Treatments include anti-inflammatory drugs and/ or alternative therapies such as acupuncture. Nutraceuticals such as glucosamine may also be helpful. Controlling exercise and maintaining your dog at an appropriate weight, are important in managing the pain.
Your veterinarian may suggest surgery (such as hip replacement) if the pain is severe, and/or can not be controlled by medical treatment as above.

For the veterinarian: 

There are several established scoring systems to evaluate radiographs for the presence of hip dysplasia. The Orthopedic Foundation for Animals evaluates a standard ventrodorsal view with hips extended and stifles rotated internally. Radiographs are scored based on degenerative joint changes and evidence of subluxation. Dogs must be 2 years of age in order to be certified by the OFA.
The PennHip method uses a quantitative measure of joint laxity (based on distraction and compression views) to determine the Distraction Index (DI), as well as the standard hip-extended view, to evaluate a dog for hip dysplasia (see Smith and McKelvie,1995, below). Dogs may be evaluated by this technique as young as 16 weeks of age.

Breeding advice: 

Canine hip dysplasia remains a problem in most large and giant breeds of dog, despite efforts to control this condition dating back to the 1960s. Because it is virtually impossible to determine the exact genotype, it is difficult to control defects like hip dysplasia that have a polygenic mode of inheritance. The best attempts at control are based on a grading scheme for identification of the defect and a breed policy of recording and publishing the results for as many dogs as possible.
Breed organizations and veterinarians in various countries have developed control programmes that rely on radiographic evaluation and a central registry of dogs. Dogs from large and giant breeds should be evaluated by one of these established screening programmes before breeding, and should be bred based on the guidelines of that programme. The distraction index (DI) is determined by the PennHip technique and is statistically the most predictive method for hip joints in pups. Essentially, the best way for breeders to prevent hip dysplasia is to breed only dogs that have disease-free joints, based on appropriate radiographic evaluation, and that come from families with disease-free joints. Do not breed dogs whose offspring have hip dysplasia (dogs with hip dysplasia can produce normal offspring, and normal-appearing dogs can produce offspring with hip dysplasia).
Two registries that keep statistics on hip dysplasia are the Institute for Genetic Disease Control (GDC - www.vetmed.ucdavis.edu/gdc/gdc.html) and the Orthopedic Foundation for Animals (OFA - www.offa.org) Thoughtful selection by breeders, using dogs from these registries, has reduced the incidence of hip dysplasia in some breeds and some areas.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources: 

Leighton EA. 1997. Genetics of canine hip dysplasia. JAVMA 210(10):1474-1479.
Martinez SA. 1997. Congenital conditions that lead to osteoarthritis in the dog. Veterinary Clinics of North America Small Animal Practice. 27(4):735-758.
Richardson DC. 1995. Developmental orthopedics: Nutritional influences in the dog. In EJ Ettinger and EC Feldman (eds) Textbook of Veterinary Internal Medicine, p. 252-258. WB Saunders Co., Toronto.
Smith GK, McKelvie PJ. 1995. Current concepts in the diagnosis of canine hip dysplasia. In JD Bonagura (ed) Kirk's Current Veterinary Therapy XII Small Animal Practice p. 1180-1188. WB Saunders Co., Toronto. Describes PennHip technique.
Smith GK. 1998. Advances in diagnosis of canine hip dysplasia. ACVIM-Proceedings of the 16th Annual Veterinary Medical Forum. p. 569-571.
Swenson L, Audell L, Hedhammar A. 1997. Prevalence and inheritance of and selection for hip dysplasia in seven breeds of dogs in Sweden and benefit cost analysis of sceening and control program. JAVMA 210(2):207-214.


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