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23 Hip Dysplasia (HD, or C(anine)HD)




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This article is from the Canine Medical Information FAQ, by Cindy Tittle Moore with numerous contributions by others.

23 Hip Dysplasia (HD, or C(anine)HD)

An _excellent_ source of information on hip dysplasia is:

Hip Dysplasia
A Guide for Dog Breeders and Owners
2nd Edition 1989
By E.A. Corley and G.G. Keller

A single copy is available for a donation and multiple copies are
$3.00 each at Orthopedic Foundation for Animals, Inc, 2300 Nifong
Blvd, Columbia, MO 65201, 573-442-0418. It is informative, and highly
recommended.

The work is copyrighted and permission to reproduce the work was not
given since the costs of production are still being recouped, so only
highlights from the monograph are presented here. I do encourage you
to get your own copy.

Another good source of information on Hip Dysplasia may be found in
the chapter "Hip Dysplasia" in _Genetics of the Dog_ by Malcolm B.
Willis (Howell Book House). Information from this chapter is also
presented below.

Other online information includes:
* http://www.working-retriever.com/library/chd6696.shtml
* http://www.idsonline.com/userweb/djones/ofahips.htm
* http://www.idsonline.com/userweb/djones/ofahipup.htm
* http://www.ici.net/cust_pages/jiminma/dysp2.htm
* http://www.biomedtrix.com/bioquest.html

In general

Hip dysplasia ("bad development") appears in people and many species
of animals. In some breeds of dogs, it is the most common cause of
osteoarthritis or degenerative joint disease. Because both humans and
dogs get hip dysplasia, dogs made a good subject to use in research.
Most of these techniques below are also used on humans.

Research on hip dysplasia suggests that CHD is a more complex disease
than was first thought. There are no simple answers or solutions to
the problem. The complexity of CHD results in research findings that
appear to be contradictory. However, many aspects of the disease have
been repeatedly and independently documented and are generally
accepted by the scientific community. Three important ones are:
* Canine hip dysplasia is caused by the presence of many genes
(polygenic). While no environmental cause has been found, many
environmental factors contribute to its expression in a particular
dog (phenotype).
* The only current means for reducing the occurrence of CHD is by
selectively breeding for normal hips.
* Radiography is the accepted means for evaluating the hip status.

Development

Regardless of what the initiating factor or factors may be, abnormal
looseness of the hip joint after 2 weeks of age seems to be the event
most commonly reported to result in hip dysplasia. However, there are
exceptions to this, and dogs with tight hips have developed hip
dysplasia.

The early changes are not easily detected. Severe cases may be
diagnosed as early as 7 weeks of age; others may not show up in
radiographs until over 2 years of age. This is why OFA only certifies
dogs over two years of age.

Breeding

Most inherited traits in animals are polygenic. These traits do not
follow patterns based on dominant/recessive pairs because polygenic
traits are affected by many genes. Only some puppies will have the
same combination of genes for a trait as the parents. Some will have a
more desirable combination while others will have a less desirable
pattern. As the number of involved genes increase, the possible
outcomes also increase. In addition, remember that it is also possible
for different genes to have a different level of influence on the
trait, complicating the outcomes considerably. Predictions of a
specific outcome from a particular mating involving polygenic traits
is currently impossible.

In Corley and Keller's opinion, a dog with excellent hips but with
more than 25% of its brothers and sisters affected with hip dysplasia
is a poorer breeding prospect than a dog with fair hips and less than
25% of its brothers and sisters exhibiting dysplasia.

 

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