Hip Dysplasia in Dogs John Foster, BVSC, CertVOphthal, MRCVS
A look back to the modern dog's wolf-like ancestor which roamed the plainsand forests millions of
years ago shows how critical it was to be able to movefreely and rapidly in search of prey. Nature
was quite uncompromising. If enough food couldn't be caught or stolen due to an inability to run, jump,
twistand turn then starvation would be the only alternative. When supper was provided by another this
need for excellence declined, so being a bit slower and being a bit stiff on a leg didn't matter so much. The dog's association with man for more than 10,000 years may appear to have been to mutual advantage but some debts wait to be paid; one of these debts concerns acondition called hip dysplasia.
Hip dysplasia (HD) is a term which encompasses a number of specfic developmental & other abnormalities involving the hip joint. Developmental changes come first and being related mainly to growth are known as primary changes. Others come later; these are related to wear and tear from usage and are termed secondary changes. The end result is that one or pair of joints becomes mechanically unsound and therefore does not function properly. An unsound joint is usually a painful one and lameness will result. In extreme cases the dog may find movement very difficult and much suffering will be involved.
It was in the light of these findings that the British Verterinary Association (BVA) and the Kennel Club (KC) developed a scheme over 30 years ago to assess the degree of hip malformation of dogs through radiography. Over this time almost 100,000 radiogarphs (X-rays) have been examined to providde a standardised opinion on HD status, principally for the use of breeders. Currently 97 breeds are surveyed by the scheme in the UK.
STRUCTURE AND FUNCTION The hip joints of land animals and even some birds are remarkably similar.
The design has with stood the test of time and usage by countless species andis close to anatomic perfection.
Where mobility, meaning athieticism, is needed the normal hip is an ideal way of enabling the transfer of power
from the hind leg muscles to the body so that the creature is driven forward with strength and speed.
The close relationship of the 'ball' to the 'socket' permits rapid changes of direction and the strength of the
supporting structures ofligaments, tendons and muscles makes the hip a unit. Large joint surfaces of cartilage
lubricated by joint fluid ensure smooth pain-free action. Little wonder,then, that any disturbance to this
ideal circumstance has such direconsequences.