Larger breed dogs have a higher risk of developing hip dysplasia, due to the greater weight these joints will have to bear. But it's important to realize that small dogs can be affected also. Large breed dogs at risk include rottweilers, german shephards, golden retrievers, dalmations, and blood hounds.

Canine hip dysplasia affects the ball and socket joint of the hip. The head of the large bone in the dog's leg doesn't fit snugly into the hip socket. The problem is that the socket itself is not well developed, and it creates a lot of stress on the joint. The muscles don't develop as quickly as the bone grows, and a situation is created where the weight the joint has to bear is greater than the capacity of the ligaments, tendons, and muscles around the joint. Thus joint instability develops. This in turn leads to a greater wear and tear than the joint would normally experience.

Canine hip dysplasia ranges from mild to moderate. In mild cases, the space between the joints is greater than normal and the ball at the top of the hip bone is part way out of its socket. Fortunately, in mild cases, there are no associated arthritic changes in the joint.

In moderate canine hip dysplasia, the top part of the normally rounded hip bone begins to flatten, and it sits only loosely in the joint. Bone spurs begin to develop, and arthritic changes start to happen.

Unfortunately, in severe hip dysplasia, there is definite arthritis present. And once arthritis appears in the joint, the condition is irreversible. In the severe cases such as this, the hip bone is completely out of the joint. The silver lining is, however, that not all dogs with hip dysplasia and arthritis will become lame. Some may become lame as puppies, some may not ever become lame.

Symptoms of hip dysplasia include:

* walking with a limp

* a swaying gait

* bunny hopping when running

* difficulty in the back legs when getting up

* pain in the hip

* when the puppy is lying on its back, its back legs may not extend towards the front legs without pain

The only way to find out if your dog definitely has hip dysplasia is if he has an x-ray by a vet. This normally means the dog will have to be heavily sedated, or go under anaesthetic.

Tips To Prevent Canine Hip Dysplasia

* Don't feed a growing dog a diet too high in calories. It's important that the growing dog's nutritional needs are met, but excessive weight, and rapid weight gain, create more of a load for the joints to bear. If a dog is genetically predisposed to hip dysplasia, this can delay the beginning of symptoms, or reduce the chance of it developing into a more severe form.

* Be careful about the type of exercise growing dogs get. Jumping up and down from heights, and standing on their back legs, such as when they stand against a fence or window to look over it, can aggravate the joints whilst they are growing quickly.

* Buy dogs from a reputable breeder. If one parent dog has hip dysplasia, the risk of it occurring in the litter is doubled. Good breeders take care to prevent this situation from occurring. The pedigrees of dogs can be checked to see whether they have been certified as normal by the Orthopedic Foundation For Animals (OFA) in the US. Their website is www.offa.org

Other organizations that check for markers of hip normalcy in dogs are PennHip and the GDC (Genetic Disease Control in Animals). Large breed dogs have a greater chance of developing hip dysplasia, and prospective owners would be wise to take this precaution.

References: J Griffin and L Carlson, Dog Owners Home Veterinary Handbook