In the days before the dog was domesticated, 'survival of the fittest' was the main rule. Dogs with serious health problems simply could not move quickly enough to catch or steal food, and starvation resulted in death. When man interfered with this natural selection process, it no-longer mattered if the dog wasn't as quick, or agile as he had been. The dog may seem to have benefited from us, as we have from him, but at a price. That price is a disease called hip dysplasia (HD).
The hip is a 'ball and socket' joint, which means that the 'ball' at the top of the femur (thigh) fits tightly into the 'socket' of the pelvis. This is such an efficient design, that the joints of land animals and even some birds are very similar. The joint has a large, cartilage-covered surface, and this is lubricated by fluid (synovial or 'joint' fluid) to ensure smooth, economical, pain-free action. When things go wrong with this efficient design, the dog is described as having hip dysplasia.
This term covers a number of developmental and other abnormalities of the hip joint. The developmental changes (primary changes) occur first, and are mainly growth related. The changes that follow (secondary changes) are related to wear and tear from usage of the defective joints. This all results in one or both joints being unable to function properly, as they are no longer mechanically sound. This usually (though not always) means the dog is lame, as the unsound joints are painful. Some dogs (like people) have a better pain-threshold than others, and as the pain tends to be constant, the dog may not show discomfort by yelping, as he would if the pain was sudden. This is why dogs can't be assessed as being free from HD without x-rays and hip scoring. This is the only accurate way, as it shows the position of the ball of the joint in relation to the socket, and also shows any secondary changes, if present.
The scheme was developed in 1965, by the British Veterinary Association and the Kennel Club, and at the moment is the most reliable method we have of checking a dog's hip status.
Because HD is defined as a 'polygenetic trait', meaning that there is more than one gene involved in producing the disease, it is not always predictable. It is also affected by environmental factors i.e. all the outside influences such as diet and exercise, to name but two. This is why dogs with good hips don't always produce these good scores in their progeny (offspring) and why we should also take account of progeny scores when planning a mating.
Apologies for the poor quality of these pictures, but this is what a good hip joint should look like. Both show scores of 0 (perfect, no hip dysplasia).
a) shows radiographic image (x-ray). b) shows line diagram of anatomical landmarks evaluated during the scoring procedure.
Good hips - note the nicely rounded femoral heads positioned snugly in the sockets
Bad hips - the femoral heads are very mis-shapen, and are hanging out of the sockets
If you haven't seen a hip scoring sheet, you've probably never heard of these technical terms. Each part is checked and given a score, and these scores are added up to give a total for each hip. The lower the score, the better the hip, with 0 being a perfect score and 53 (single hip) being severely dysplastic, the worst score possible. The two scores (one for each hip) are then quite often totalled together to give a final score.
There are two very informative leaflets on HD, both available from the B.V.A. (British Veterinary Association, Canine Health Schemes, 7 Mansfield Street, London, W1M 0AT, Tel 0171 636 6541). The first is 'Hip dysplasia in dogs' written by John Fisher, and is a basic guide for dog owners. The second, 'The BVA/KC scoring scheme for control of hip dysplasia: interpretation of criteria' is more advanced, but very good, especially for people who do use the scheme.
Unfortunately, this scheme has its restrictions, the main one being that you can't score the dog 'til it's 12 months old, and by this time it may have become a much loved family pet, or successful show dog. The second is that according to American research, the way we position the dogs for scoring doesn't give a true picture. They have pioneered a new way of x-raying that appears to give more accurate results, and can be used much earlier. The main reason that it isn't available in this country is that there needs to be some-one present to position the dog while the x-ray is being taken, which is not allowed in this country.
For more information on this new scheme, called the PennHIP scheme, there is a very good article written by Fred Lanting, THE non-veterinary expert on hips, and author of "Canine Hip Dysplasia" and "The Total GSD". More info on PennHIP
Another excellent source of information on the disease is the book "The German Shepherd Dog, A Genetic History of the Breed", by Dr. Malcolm B. Willis, the breed geneticist in this country.