Canine Hip Dysplasia as influenced by genetic and environmental

For more than 50 years, screening for hip conformity and breeding for sound hips have been on the agenda of the veterinary profession and dog breeders not only in Europe but all around the world.
When it became evident that one of the more common causes of lameness and pain in the hind limbs of dogs was a malformation of the hips, the condition was named canine hip dysplasia after a similar condition in man. It has, however, dissimilarities as well as similarities with its human counterpart [Schnelle et al 1959].
We all agree nowadays that hip dysplasia in dogs is a developmental disorder under the influence of several genes as well as various environmental influences. Over the years we have learned more about its heritability but also how environmental factor may influence its occurrence and severity. However, despite great efforts it is still a major cause of disabilities and even euthanasia in many of the larger sized breeds. Much effort has been focused in the past on the phenotypical appearance of hip dysplasia and sophisticated methods have been developed to measure and grade various components of the dysplasia. These includes shallowness, laxity and secondary changes in structures of the hip joint. Unfortunately less has been done to influence the extent to which these measures are taken into account in the selection of breeding stock. Whatever method is used to measure, grade and define hip dysplasia it is well proven that dysplastic parents are more likely to produce affected progeny and more severely affected progeny [Hedhammar et al 1979]. Consistent breeding from phenotypically unaffected breeding stock does decrease the prevalence of hip dysplasia in closed breeding colonies as well as in various breed populations in several countries [Swenson et al 1997, Reed at al 2000]. Our current efforts are based on extensive screening programmes in many countries but there are too few well functioning breeding programmes. The scientific commission of FCI have made efforts to harmonise the screening procedure and to introduce a quality control programme for the technical screening procedure as well as the evaluation of radiographs by ‘validated’ panellists. An advisory group of experts, including all the speakers at this symposium, was appointed at a meeting in Copenhagen to propose clarifications and changes to the current FCI Hip Dysplasia protocol. To
optimise proper usage of hip dysplasia screening procedures it is equally important to develop and exchange experiences of successful breeding programmes. Let us critically review what is currently known about the genetics and environmental influences of hip dysplasia and, based on that, reconsider our strategy to screen, breed, feed and treat dogs with reference to canine hip dysplasia.