Hip Dysplasia Treatment and Information



Longlife Program #3

What is Hip Dysplasia?

Hip dysplasia is the abnormal function of the hip joint, which occurs when the fit between the ball and socket of the hip joint loosens. Most of the problems resulting from hip dysplasia are a result of this looseness, the loss of tension in the muscles, connective tissue, and ligaments that should support the joint. Symptoms are bunny hopping, side sitting, limping, lying in unusual positions, and refraining from jumping.

How Does Longlife Treat Hip Dysplasia?

Longlife for Dogs contains pure shark cartilage, specially processed for maximum absorption into the bloodstream by your dog's digestive system. It contains Amino Acids and High Proteins, with natural Mucopolysaccharides, which promote the generation of new cartilage cells - a major factor in stiffness and inflammation associated with over-exertion or arthritic joints.

Understanding the Canine Hip Joint

To understand what hip dysplasia really is, one must start with an understanding of the hip joint. The hip joint forms the attachment of the hind leg to the body by way of a “ball and socket.” The ball portion is the head of the femur (the long bone extending from the hip to the knee), while the socket (known as the acetabulum) is located on the pelvis. In a normal joint, the ball rotates freely, and snugly, within the socket. To facilitate movement, the bones are shaped to match each other perfectly, with the socket surrounding the ball. The two bones are held together by a ligament, which strengthens the joint, and attaches the femoral head directly to the acetabulum. The joint capsule, which is a very strong band of connective tissue, encircles the two bones and adds further stability. The area where the bones actually touch each other, the articular surface, is perfectly smooth and cushioned with a layer of spongy cartilage. In the normal dog, all of these factors work together to facilitate smooth movement and stability.

A good hip joint has a neat, snug fit between the ball and socket; the head of the femur should not be riding around somewhere in the neighborhood of the acetabulum. CHD occurs when the hip joint loosens. Most of the problems resulting from hip dysplasia are a result of this looseness: a loss of tension in the muscles, connective tissue, and ligaments that should support the joint. Most dysplastic dogs are born with normal hips, but due to genetic and possibly other factors, the soft tissues that surround the joint start to develop abnormally as the puppy grows. The most significant of these changes is that the bones are not held in place but actually move apart. The joint capsule and the ligament between the two bones stretch, adding further instability to the joint. As this occurs, the articular surfaces of the two bones lose contact with each other. This separation of the two bones within a joint, called subluxation, causes all the resulting problems we associate with the disease.

There are infinite variations of dysplasia, ranging from only very slight dysfunction to complete dislocation. Consequently, no two dogs will be affected by CHD in exactly the same way.

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Risk Factors for Hip Dysplasia

The basis for CHD is the dog’s genetic makeup, which can be measured by what is termed the Heritability Factor. Heritability is measured on a scale from zero to one, with a condition totally unrelated to genetics (such as a traumatic injury) measured at zero and a condition entirely determined by genetics (such as gender) measured at one. Studies have shown that CHD's Heritability factor ranges from .25 to .85, which indicates a significant genetic contribution. Therefore, if the parents are carrying genetic material for CHD, the offspring is guaranteed at least to carry the gene. And the greater the Heritability Factor for loose hips or malformed bone or abnormal muscle mass from the parents, the greater the chances for hip dysplasia in the offspring.

The expression of hip dysplasia in any dog has other determinants, though; genetics are only one factor in the total picture. The effect of the developing dog's environment does play a role in the observable signs of dysplasia, although just as with the genetic component, the effects of environment are variable and not completely understood. In other words, it is possible for a dog with known genetic components for hip dysplasia not to show any clinical signs of trouble if the environmental factors are favorable, or not to show observable signs of it until middle or old age.

Genetic CHD factors in dogs are distributed unevenly across certain breeds. CHD is primarily a disease of large and giant breeds, though it can occur in medium-sized breeds and rarely in small breeds. It primarily afflicts purebreds, although it can happen in mixed breeds, particularly a cross of two dogs that are prone to developing the disease. German Shepherds, Labrador Retrievers, Rottweilers, Great Danes, Golden Retrievers, and Saint Bernards appear to have a higher incidence, but these are all very popular breeds and may be over-represented because of their popularity. Other high-risk breeds include the: American Bulldog, American Staffordshire Terrier, Beagle, Bernese Mountain Dog, Bloodhound, Bouvier des flandres, Boykin Spaniel, Briard, Brittany, Bulldog, Bullmastiff, Chesapeake Bay Retriever, Chow Chow, Clumber Spaniel, Coonhound (Black and Tan), Coton de Tulčar, Curly Coated Retriever, English Setter, English Springer Spaniel, Giant Schnauzer, Gordon Setter, Irish Water Spaniel, Kuvasz, Neapolitan Mastiff, Newfoundland, Norwegian Elkhound, Old English Sheepdog, Otterhund, Polish Lowland Sheepdog, Portuguese Water Dog, Pudel Pointer, Pug, Rottweiler, Shih Tzu, Spanish Water Dog, Staffordshire Terrier, Sussex Spaniel, Welsh Corgi, and Welsh Springer Spaniel. Greyhounds and Borzois have a very low incidence of the disease.

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Formula for Determing a Dog's Predisposition to CHD

The formula for determining any dog's predisposition to CHD is complex, taking into account not only genetics and breed but a whole host of contributing factors. It must be stated that some researchers believe that genetics is the only factor involved, whereas others think genetics contributes less than 25% to the development of the disease. The truth probably lies in the middle. If there are no genetic carriers of hip dysplasia in a dog's lineage, then it will not contract the disease. If there are genetic carriers, then it may contract the disease. The incidence of hip dysplasia can be greatly reduced through a certain type of selective breeding, as well as increased. However, the disease cannot be completely avoided through selective breeding. In other words, if two dysplastic dogs are bred, the offspring are much more likely to develop the disease, but will not all have the same level of symptoms, or even necessarily show any symptoms. The offspring from these dogs will, however, be carriers and the disease may show up in their offspring in later generations. This is why it can be difficult to eradicate the disease from a breed or specific line, or even to produce the conditions under which the disease would be guaranteed to occur. The following factors affect a dog to varying degrees:

Nutrition: A key contributor to CHD is obesity. The effort of carrying extra weight will exacerbate degeneration of the joint in a dog with a loose hip. Overweight dogs are therefore at a much higher risk. Another factor that might increase the incidence is rapid growth in a puppy during the ages from three to ten months. Experimentally, the incidence has been increased in genetically susceptible dogs when they are given large-quantity/large-calorie diets. A 1997 study showed that Labrador Retriever puppies that were fed a high-protein, high-calorie diet free choice for three years had a much higher incidence of hip dysplasia than their littermates who were fed the same high-calorie, high-protein diet, but in an amount that was 25% less than what was fed to the dysplastic group. As might be expected, however, the free choice group was significantly heavier at maturity, averaging 22 pounds heavier than the control group.

There have also been studies examining protein and calcium levels and their relationship to hip dysplasia. These studies found that increased amounts of calcium and protein in the diet were correlated with a higher incidence of hip dysplasia. But once again, these studies compared puppies fed greatly increased amounts over normal recommended values to animals fed decreased amounts. They failed to compare puppies fed a normal amount of food that had the recommended amount of protein, fat, and calcium to those fed a diet with slightly less protein, fat, and calcium (similar to those “large breed puppy foods” that are now flooding the market). No studies link an increased incidence in hip dysplasia in dogs fed a normal diet of commercial puppy food versus a specialty diet formulated just for large breed puppies.
Some reports indicate that in puppies a restricted calorie intake could restrict the growth rate, and in turn lessen the likelihood of the dog developing hip dysplasia. The problem with this is that some restricted diets restrict the fat and protein content and increase the carbohydrate content of the food. A pet owner’s real goal should be to keep growing pups from becoming overweight. Restricting fat and protein in a growing pup can be a disaster. A high-quality, meat-based diet is absolutely necessary for growing pups, as long as the owner does not feed the puppy so much that it becomes overweight.

Exercise: A young, growing dog with a genetic makeup for CHD will be more likely to develop arthritis and have more difficulty in the long term if it is highly active physically. Climbing stairs, jumping, and running can all subject the growing hip structures to unwarranted stress and trauma and increase the risk of future discomfort for the dog. The effects of excessive activity are worsened in an overweight pup. (In a normal, growing dog, these activities will not cause hip dysplasia.)

In short, it appears that dogs that are genetically susceptible to the disease may have an increased incidence of disease if they over-exercised at a young age. At the same time, we know that dogs with large and prominent leg muscle mass are less likely to contract the disease than dogs with small muscle mass. So, exercising and maintaining good muscle mass may actually decrease the incidence of the disease. Moderate exercise that strengthens the rump, or gluteal muscles, such as running and swimming, is probably a good idea, whereas activities that apply a lot of force to the joint, such as jumping during a game of Frisbee, are contraindicated.

The Pectineus Muscle can contribute to the worsening of hip dysplasia. In a dog with a strong genetic background for CHD, the microscopic makeup and contractibility of the Pectineus Muscle are strikingly different from the corresponding muscle of a normal dog. The theory is that a tight or inelastic Pectineus Muscle causes tension in such a way that the force tends to pull the head of the femur away from the acetabulum, increasing looseness in the joint. I have had good results in about 50% of the cases in which I have surgically excised a portion of the Pectineus Muscle. The patients were more comfortable and mobile almost immediately. This Pectineal Myotomy surgery has no effect on the arthritic changes in the hip joints, but it can make the dog more comfortable.

Surfaces: There is no scientific proof that surfaces have an impact on the disease, but many observers conclude that pups reared, especially during the nursing period, on slippery surfaces such as newspapers will be prone to hip difficulties. Smooth concrete or wood surfaces may not cause dysplasia, but they can make a bad situation worse. Better surfaces for newborn pups are blankets or towels—surfaces they can grip.

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Symptoms of Hip Dysplasia

The symptoms of CHD can be the same as those often found in many other ailments: hip soreness, difficulty arising or climbing inclines, and limping. However, a few very specific symptoms can be signs of CHD:

Bunny Hopping: The dog tends to use both hind legs together, rather than one at a time. This occurs when the dog is running or going up stairs.

Side Sit: Also called lazy sit, slouch, or frog sit. When the dog sits, its legs are not positioned bent and close to the body. They can be loose and off to one side, or one or both legs may be straight out in front.

Sway Walk: Also called a loose walk. When the dog is walking, the back end sways back and forth because the hips are loose. The dog seems to be tiptoeing or walking very lightly on its rear legs. A dysplastic dog will be reluctant to jump or "stand up" on its hind legs.

Unusual Lying Position:Legs are straight out and off to the side when the dog is lying on its stomach or legs are straight out behind the dog. (All dogs lie with their legs behind them on occasion, but many dogs with hip dysplasia lie like this all the time.)

Limping: The dog may favor one hind leg or the other, and may alternate legs that it is favoring.
Doesn’t Jump: Not only does the dog not jump on you, it seems to pull itself up by its front end onto furniture instead of jumping up.

Underdeveloped Hind Quarters and Overdeveloped Chest: This is caused by the failure to use the hind legs normally and jump. The dog also may actually be shifting weight forward.

Occasionally the symptoms break down by age:

Symptoms in young dogs: Puppies who are already in pain from hip CHD tend to be very good puppies. They do not roughhouse the way that normal puppies do, and they tend to sleep for a long time after playing or going for a walk. Some owners describe their puppy as the best puppy they’ve ever had. The second warning sign is a puppy that runs with both back legs nearly together, almost as a bunny hop (see above). After exercise the puppy might be reluctant to rise, will sit back as if unsteady, and (this will be most apparent) will have difficulty climbing stairs or inclines. The puppy might look slightly underdeveloped in the rear quarters. When it stands the rear legs may not be parallel, but rather too close together at the ankles. This is a condition called "cow hocked." An owner might notice a boniness to the pelvic area from lack of good muscle development. Another hint of trouble is an inability to extend the leg backward very far (decreased range of motion).

Signs usually become evident between five and eights months of age. But remember, as we learned above, some dogs do not show any signs at all of hip joint degeneration until adulthood.

Symptoms in breeding dogs: Those looking to breed their dogs (especially for competition) should have an X-ray in all circumstances. In one test case, a Golden Retriever had absolutely no outward symptoms. He jumped and swam and had never shown any kind of lameness. In preparation for breeding, the owner had the dog X-rayed, and the X-ray displayed severe abnormalities in the left hip joint. Were the changes due to a genetic propensity for hip joint abnormalities, or was this actually due to an injury early in the pup's life that impacted the proper growth of the joint structures? No one can say for certain. But if the abnormal hip was due to genetic determiners, why take a chance of the litter having even worse hip joint conformation? (Note: The owner decided not to breed the dog.)

Signs of CHD in older dogs: Some dogs with dysplasia escape pain or simply accept it as a fact of life—at least for the first few phases of life. In fact, they don't complain until degenerative joint disease sets in. Affected older dogs will sit rather than stand, have trouble arising, run with the rear legs together, and be unable to keep up speed on walks. Every veterinarian has been mystified, from time to time, when an X-ray of an older dog who only recently seemed to be having hip trouble revealed extensive degenerative changes in the hips due to long-term dysplasia.

It is very important to keep this fact in mind: A dog can appear normal and yet have hip dysplasia. Just because a four-year-old dog isn't showing signs of trouble does not mean it doesn’t have hip dysplasia or won’t in the future.

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Hip dysplasia diagnosis

Diagnosis of hip dysplasia in dogs is usually made by a veterinarian through a combination of a physical exam and X-rays. The veterinarian may even be able to feel looseness in the joint or may be able to elicit pain through extension and flexion. Regardless, the results are straightforward and usually not difficult to interpret.

However, about half of the animals that come in for a determination on the health of their hip joints are not showing physical signs, but are intended to be bred. The breeder wants to ensure that the animal is not at great risk for transmitting the disease to his or her offspring.

Hip Dysplasia Testing Methods

There are two different testing methods that can be performed: the older OFA testing and the newer Penn HIP method.

OFA: The method used by the Orthopedic Foundation for Animals (OFA) has been the standard for many years. The OFA maintains a database of hip evaluations for almost half a million dogs. Radiographs are taken by a local veterinarian under specific guidelines and are then submitted to the OFA for evaluation of hip dysplasia and certification of hip status. Since the accuracy of a dog’s diagnosis of hip dysplasia using the OFA technique increases after 24 months of age, the OFA requires that the dog be at least two years of age at the time the radiographs are taken. They also recommend that the evaluation not be performed while the female is in heat. To get the correct presentation and ensure that the muscles are relaxed, the OFA recommends that the dog be anesthetized for the radiographs. OFA radiologists evaluate the hip joints for congruity, subluxation, the condition of the acetabular margins, and acetabular notch, and the size, shape, and architecture of the femoral head and neck. The radiographs are reviewed by three radiologists and a consensus score is assigned based on the animal's hip conformation relative to other individuals of the same breed and age. Using a seven-point scoring system, hips are scored as normal (excellent, good, fair), borderline dysplastic, or dysplastic (mild, moderate, severe).

PennHIP: The diagnostic method used by the University of Pennsylvania Hip Improvement Program (PennHIP) uses distraction/compression radiographic views to more accurately identify joint laxity. Radiographs of the hip joints are taken with the dog under heavy sedation. Two views are obtained with the hind limbs in neutral position; this maximizes joint laxity. Weights and/or other devices are used to help push the head of the femur further into or away from the acetabulum. The amount of femoral head displacement (hip joint laxity) is quantified using a distraction index (DI). The DI ranges from 0 to 1. It is calculated by measuring the distance the center of the femoral head moves laterally from the center of the acetabulum and dividing it by the radius of the femoral head. A DI of 0 indicates a very tight joint. A DI of 1 indicates complete luxation with little or no coverage of the femoral head. A hip with a distraction index of .6 is 60% luxated and is twice as lax as a hip with a DI of .3. When the DI was compared to the OFA scores for 65 dogs, all dogs scored as mildly, moderately, or severely dysplasticby the OFA method and had a DI above .3.

Hip joint laxity as measured by the DI is strongly correlated with the future development of osteoarthritis. Hips with a low DI are less likely to develop osteoarthritis. Hips with a DI below .3 rarely develop osteoarthritis visible on radiographs. Although hips with a DI above .3 are considered "degenerative joint disease susceptible," not all hips with a DI greater than .3 eventually develop osteoarthritis. It is known that some hips with radiographically apparent laxity do not develop osteoarthritis. A means of differentiating lax hips that develop osteoarthritis from those that do not is important in developing a prognosis and making treatment recommendations. In one study, the DI obtained from dogs at four months of age was a good predictor of later osteoarthritis, though the 6- and 12-month indices were more accurate.

To assure quality and repeatability among diagnostic centers using PennHIP, veterinarians must take a special course and become certified. As this technique gains popularity, more veterinarians are becoming certified.

Anesthesia: During the diagnosis, anesthesia is necessary. To yield an X-ray with the information the owner is trying to discover, the dog must be perfectly relaxed. Because the position required to take a diagnostic X-ray is unnatural, even very gentle, cooperative dogs cannot relax enough to be X-rayed properly. It is frustrating for the veterinarian for an owner to claim that anesthesia is not necessary, that the dog will “do anything you tell it to.” Unless at the time of exposure of the X-ray the dog is positioned precisely, with no movement, the X-ray will not be credible.

Another great advantage of anesthesia is that it allows the veterinarian to palpate and manipulate the hips to actually feel the degree of looseness. Also, the tension of the Pectineus Muscle is best assessed under anesthesia. Any grating or grinding from calcium deposits along the hip joints can be evaluated better in a sleeping dog than in one that is awake. Let sleeping dogs lie, indeed. If the pelvis is tipped only slightly to one side or the other, one hip that isn’t normal can appear to be and one that is not dysplastic can appear to be. To complicate things, 10% of dysplastic dogs will be affected in only one hip. The X-ray should be done right.

X-rays can be done as early as at five or six months of age, if dysplasia is suspected. The advantage of radiography in a younger animal is that if you plan to breed it, you can save the time and financial and emotional expense related to breeding if the X-rays show unquestionable hip dysplasia. Again, the advantage of the PennHIP procedure is obvious, since dogs over four months of age can be evaluated.

It is very sad indeed for any pet owner to see his or her special pal affected by the discomfort and mobility problems associated with Canine Hip Dysplasia. Armed with knowledge and forethought, highly selective breeding is your best defense against CHD.

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Effects of Hip Dysplasia on the Muscles

Research has shown that dogs with CHD have significantly decreased sizes of total pelvic musculature surrounding and acting on the hip joint. Whether this is a contributing factor or a result of hip dysplasia remains to be proven. One muscle that can contribute to worsening of hip dysplasia is the Pectineus Muscle. (See Exercise section.)

Effects of Hip Dysplasia on Ligaments

Attaching to the head of the femur from the center of the hip socket is a tough fibrous ligament called the Ligament of the Head of the Femur. If this ligament is stretched or torn, the hip joint will be less stable—and this is exactly what happens to dogs with dysplasia. In fact, some of the first changes to take place in young dogs developing hip dysplasia occur in this ligament, especially if the muscle mass of the pelvis is underdeveloped. The ligament swells, develops tiny tears, and then stretches. In advanced CHD, the ligament can totally break down and cause more harm than good.

Effects of Hip Dysplasia on Joints

The joint capsule surrounds the joint and produces synovial fluid to nourish and lubricate the joint cartilage. In addition, the joint capsule provides some support to the joint. In dysplastic joints, the capsule becomes irritated, stretched, and scarred. In advanced cases the capsule loses its elasticity and inhibits a full range of motion in the joint. A lot of the pain associated with hip dysplasia originates from inflamed nerve endings in the joint capsule, so any pathology here will have a noticeable effect on the dog.

Cartilage

The surfaces of the head of the femur and the acetabulum are covered with what is termed hyaline cartilage. In a dysplastic joint, the points of pressure and the amount of pressure applied to areas of cartilage surfaces are abnormal. The cartilage is not able to function as it should, so it changes or disintegrates as a response. The changes range from thickening in abnormal areas to thinning in others. Sometimes the pounding it takes erodes the cartilage down to the underlying bone. The result is more pain and discomfort, more inflammation, more calcium deposits from inadequate healing attempts, and eventual breakdown of the joint as a unit. Nutriceuticals, such as Chondroitin Sulfate and Glucosamine, may be effective in aiding the repair and maintenance of this articular cartilage.

Bone Changes

Since bone is alive, it responds to stress and grows in a manner that tends to distribute weight loads evenly. As a result of posture changes brought on by discomfort, the dog's weight-bearing forces stress the bone in unnatural ways. The bone does what it is supposed to do in response and changes its shape.

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Hip Dysplasia Prevention

There are many different theories on how to prevent the progression of hip dysplasia. Nutrition, exercise, and body weight may all contribute to the severity of degenerative joint disease after hip dysplasia has developed. New information concerning other factors that contribute to hip dysplasia may come forward in the future, but for now, we have to stick to what we know for sure. (If owners insisted on only purchasing an animal that had parents and grandparents with certified good or excellent hips, then the majority of the problems would be eliminated. This is, of course, cold comfort to those needing care for dogs they already own.) Following the newer recommendations for exercise and nutrition may help, but will never come close to controlling or eliminating the disease if stricter requirements for certified hips are not instituted or demanded.

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