A dog has hip dysplasia if either or both of the hip joints have failed to develop normally. The hip joint is formed by the ball at the head of the thigh bone and a socket in the pelvis. The ball should fit snugly into the socket. When the fit is poor, wear occurs to the surfaces of the joint causing damage to the joint, cartilage and bones and the development of arthritis.
Hip dysplasia occurs in many animals, including the Golden Retriever and several other dog breeds. The condition results from a combination of genetic and environmental factors. Hip dysplasia is a polygenic condition; caused by the cumulative effects of a number of genes which affect the growth and development of the hip joint. Because of the number of factors involved, the expression of hip dysplasia varies considerably from one dog to another.
Environmental stresses affecting hip dysplasia include the dog’s rate of growth, his weight and the amount and type of exercise. Allowing a puppy to grow too quickly, become overweight and to jump and run about on slippery surfaces increases the likelihood of poor bone and joint development. Inappropriate exercise such as accompanying a jogger or running with a bike while his bones are developing also increases the risk.
There is no way to be absolutely sure that your puppy will not develop hip dysplasia. A history of parents, siblings and grandparents which have low scores reduces the possibility of your puppy having a high score. There is evidence that a selective breeding program can reduce the number of dogs affected with hip dysplasia.
Dogs used for breeding should be scored under an accredited hip and elbow scheme. The AVA (Australian Veterinary Association) and the BVA (British Veterinary Association) schemes use X-rays of the hip joints which are evaluated by accredited scorers. The scoring is done by assessing nine different aspects of the hip X-ray. Each aspect except for one is scored between 0 and 6. The aspects evaluated are the Norberg angle, subluxation, cranial acetabular edge, dorsal acetabular edge, cranial effective acetabular rim, acetabular fossa, caudal acetabular edge, femoral head/neck exostosis and femoral head re-contouring.
Hip scores range from 0:0 (0) to the highest score possible 53:53 (106). Each hip joint is given a score between 0 and 53 and a total score is reported e.g. 5:9 (14). A perfect ball and socket joint has a score of zero. A dog with two perfect hips has a score of 0:0 (0) but very few Golden Retrievers have perfect hips. A slight irregularity in the ball or socket may give a score of 2:3 (5). The more irregular the ball and socket becomes, the higher the resulting score. A lower score means better hips. Golden Retrievers with high hip scores should not be used for breeding.
The breed mean score is calculated from the X-rays submitted to the scheme. This sample is only a small proportion of the Golden Retriever population.
The hip score of a dog should only be a part of his assessment. A good hip score means that the dog has good hip structure. It says nothing about his value to the breed. Many other factors including temperament and conformation must also be evaluated when deciding the breed worth of any dog.