Hip Dysplasia

In dogs, hip dysplasia is an abnormal formation of the hip socket that, in its more severe form, can eventually cause crippling lameness and painful arthritis of the joints. In essence, the ball of the femur can not fit properly into the hip socket. An affected dog may show absolutely no signs of this condition, whilst others may show severe signs. It is a genetic (polygenic) trait that is affected by environmental factors. It can be found in many animals and in humans, but is most commonly associated with dogs, and is common in many dog breeds, particularly the larger breeds.

Hip dysplasia is one of the most studied veterinary conditions in dogs, and the most common single cause of arthritis of the hips.

Causes of hip dysplasia

Several factors contribute to the development of this problem. Some breeds are more likely to genetically inherit hip dysplasia. Environmental factors also play a role in the development of dysplasia including diet, weight gain and exercise.  Research has shown that the cause of hip dysplasia is related to a combination of genetic and environmental factors. The disease is known to be an inherited condition and the genetics of hip dysplasia are extremely complicated. In addition, environmental factors such as overfeeding and excessive exercise can predispose a dog (especially growing puppies) to developing hip dysplasia.

Reducing the incidence of Hip Dysplasia

The British Veterinary Association (BVA) in conjunction with the Kennel Club (KC) established a hip scoring scheme in the 1970s. The Australian Veterinary Association established the Australion hip scoring scheme largely based on the BVA model. As of January 2016 the scheme is now managed by the ANKC. The AVA / ANKC Canine Hip & Elbow Dysplasia Scheme (CHEDS) ensures dog's x-rays are scored by an expert. Since in some HD prone breeds it is virtually impossible to find an animal that is hip dysplasia free, the object is to ensure that you breed from a dog whose score is better (lower) than the breed average score. In this way the chances of reducing the incidence of the disease are greatly increased. All breeding stock should be x-rayed and scored to minimise incidence of hip dysplasia in the Rhodesian Ridgeback breed.

Hip Scoring

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. .

Hip scores range from 0:0 (0) to the highest score possible 53:53 (106).  A lower score means better hips. Each hip joint is given a score between 0 and 53 and a total score is reported A dog with two perfect hips has a score of 0:0 (0). 

The breed mean score is calculated from the X-rays submitted to the scheme over the previous five years. As of 2016 the breed mean for Rhodesian Ridgebacks scored in Australia is 5.

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.

Diet and exercise in growing dogs

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The procedure is as follows:

(a) dog must be over one year old and x-rayed by a veterinary surgeon

(b) general anesthesia is necessary in order that correctly positioned plates are obtained.

(c) x-rays are then submitted to, and the hips are assessed by, a veterinary radiologist and a score awarded and reported to the veterinary surgeon.

There is a growing body of evidence indicating that dogs that grow very rapidly are more likely to have hip dysplasia. Many authorities recommend feeding a specifically formulated puppy food to puppies of high-risk breeds so their growth is slower. They will still reach their full genetic body size, but just not as rapidly.

Avoid excessive exercise in a growing puppy. Any abnormality in the structure of the hip joint is magnified if excessive running and jumping occur. It is not necessary to treat your puppy as if it were disabled, but long sessions of running or repetitively chasing thrown objects, running on the beach or alongside a bike can be detrimental to joints.

References

"Hip Dysplasia (Canine)" Wikipedia.

"Hip Dysplasia in Dogs" VetWest Animal Hospitals

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