Hip Dysplasia

OVERVIEW: 

 

Hip dysplasia is one of the most common serious genetically inherited disorders in domestic dogs, and is probably the most common in large and giant breeds.  Hip dysplasia is caused by a malformation of the hip joint.  In a dog’s hip, the head of the femur, or upper leg bone, connects to the hip by fitting into the acetabulum, a rounded concave socket.  In a healthy dog, the femur head, or caput, fits nearly perfectly into the acetabulum, both of which are coated in a protective layer of cartilage.  This cartilage prevents the two bones from rubbing directly against each other and causing damage.  Dysplastic dogs, or those suffering from hip dysplasia, have something wrong with the shape of the femur, shape of the acetabulum, the cartilage in between them, or possibly some combination of the three.  Although there are many variations, two types of malformations are the most common.  In many cases, the caput does not fit snugly into the acetabulum as it should, but rather loosely or sometimes only partially.  It is also very common for the caput, acetabulum, or both to be misshapen.  In most cases, the same deformities will be found in both hind legs, meaning that the dog will have hip dysplasia in both legs.  Although rare, it is not unheard for only one side of the hip to be dysplastic.

 

Malformations of the hip joint cause many problems for the dog.  If the caput is not snug within the acetabulum, it may move around within the hip joint and may connect with bone in cartilage in unnatural and improper ways.  This also usually weakens the hip and renders it incapable of supporting as much weight as it could if it were normal.  If either the caput or the acetabulum is misshapen, they will rub up against each other improperly.  Either situation causes unusual friction on the bones, friction they were not designed to withstand.  Because the cartilage often cannot withstand this friction, it is damaged over time.  The dog’s body attempts to make up for this damage by constantly producing new cartilage.  Unfortunately, cartilage production is a very slow process which can only rarely keep up with the increasing cartilage damage.  As the cartilage wears down, the hip begins to degrade as well.  This degradation substantially worsens if the cartilage wears down entirely and the bones begin to connect directly with each other.  These problems lead to inflammation within the joint, which in turn leads to pain.  The more damage the hip joint takes, the less able it is to resist further damage.  This leads to a vicious cycle of increasing damage to the joint.  In turn, this leads to increasing pain for the dog.  The impacts of hip dysplasia are largely dependent on how much pain the dog is in and how it handles pain.  Some dogs may not seem affected at all by very severe hip dysplasia while others may be nearly crippled by comparatively minor hip dysplasia.  In most cases hip dysplasia will result in difficulty moving, chronic arthritis, and muscle atrophy.  In severe cases, it can lead to total lameness in one or both hind legs.  Dogs often adapt to their hip dysplasia by moving in a manner which causes them the least pain, such as “bunny hopping.”  Because these forms of movement are unnatural, if they are repeated over time they can cause a number of additional musculoskeletal problems.

 

Hip dysplasia is almost certainly the most studied problem in modern canine medicine.  The condition has been known for decades and intensive research has been conducted since the 1950’s and 1960’s.  A number of national militaries have even conducted intensive studies on the condition because it impacts their police and military dogs at high rates and renders them incapable of performing their duties.  Even after all this time and research, the causes of hip dysplasia are still poorly understood.  It is very clear that the condition is inherited and usually runs in family lines.  However, it is equally clear that hip dysplasia is a polygenic condition, meaning that multiple genes influence its development.  Polygenic conditions are the hardest to figure out an inheritance mechanism for because every gene that influences them has to be studied.  Hip dysplasia is also problematic because different problems may be caused by entirely different sets of genes, and the same problem may be caused by different genes in different breeds.  Although long assumed to be entirely genetic, recent research indicates that there is a substantial environmental component to hip dysplasia as well.  There is now nearly universal agreement that environmental factors such as diet, weight, exercise, and speed of growth influence the age of the onset of hip dysplasia’s symptoms as well as their severity.  Some research indicates that such factors may even partially determine whether a dog develops hip dysplasia at all but this has proven to be substantially more controversial.

 

Hip dysplasia is extremely common and has been diagnosed in almost every single dog breed with a few notable exceptions.  However, the condition is much more commonly seen in large dogs, especially massive ones.  The condition is also considerably more common in purebreds than mixes, especially purebreds that have been the victims of copious amounts of backyard and commercial (puppy mill) breeding practices.  It has long been assumed that large dogs are more vulnerable because they have a greater genetic propensity towards the condition than small dogs, which is certainly true in the case of some breeds.  However, recent environmental studies suggest that small dogs may be less likely to develop hip dysplasia only because of environmental rather than genetic factors, such as the fact that their greatly reduced weight puts a substantially lighter burden on their hip and the tendency for owners to exercise them less.  Dogs of any age may develop hip dysplasia, but it is most commonly diagnosed in dogs between the ages of 6 months and 3 years and then again in dogs over the age of 7.

 

RISK FACTORS: 

 

The following factors have either been shown to or are widely believed to increase both a dog’s likelihood for developing hip dysplasia and/or for having more severe problems.

 

Weight – Overweight dogs are considerably more likely to have severe hip dysplasia symptoms than dogs of proper weight.

 

Size – Hip dysplasia is common in dogs of all sizes, but is substantially more prevalent in large dogs.  As a general rule, the larger the dog, the more likely it is to develop hip dysplasia.

 

Build – Dogs with thicker, stockier bodies are more likely to develop hip dysplasia.  Additionally, dogs with aberrant body types (those that are the least similar to the wolf) are more likely to develop hip dysplasia.

 

Age – Because hip dysplasia is present from birth, dogs of all ages may exhibit symptoms.  However, the condition has a very strong age component, and the older the dog, the more likely it is to exhibit symptoms.
Genetics – Hip dysplasia is a genetically-inherited condition so dogs whose close relatives have had hip dysplasia are considerably more likely to develop the condition.  In fact, there is probably no greater predictor of whether a dog will develop hip dysplasia than genetics.  This is not a rule, however, and two perfectly normal parents may have a severely dysplastic offspring and vice versa.

 

Breed -  After family history, there is probably no greater risk factor for hip dysplasia than breeds.  Although the condition has been identified in most breeds (with a very, very short list of exceptions), hip dysplasia is dramatically more common in some breeds than others.  According to the OFA, the English Bulldog is the most likely breed to suffer from hip dysplasia, with an estimated 72.1% dysplastic and only 0.2% being excellent.  Behind the English Bulldog are the Pug (66% dysplastic, 0% excellent), Dogue de Bordeaux  (56.7% dysplastic, 1% excellent), and Otterhound (51.1% dysplastic, 0.3% excellent).  Other breeds which had more than 40% of all breed members being found dysplastic include the Boerboel, Neapolitan Mastiff, St. Bernard, Clumber Spaniel, Black Russian Terrier, Sussex Spaniel, Dogo Argentino, and Cane Corso.  Hip dysplasia is regarded as one of the most serious problems in a very large number of breeds, even those that are not nearly as high on the OFA’s list.  Some of the most famous include the German Shepherd Dog, Belgian Shepherd Dog (Malinois), Labrador Retriever, Golden Retriever, French Bulldog, American Bulldog, American Pit Bull Terrier, American Staffordshire Terrier, Newfoundland Dog, Bloodhound, Louisiana Catahoula Leopard Dog, and Rottweiler.

 

 

SIGNS & SYMPTOMS: 

 

Unfortunately, most of the signs of the early stages of hip dysplasia are entirely internal and cannot be identified without x-rays or other similar procedures.  It is only when hip dysplasia has advanced to the point where the dog is in serious pain and/or discomfort that the owner becomes aware, and then usually only by behavioral changes.  Most dogs with hip dysplasia begin to display either difficulty moving or a reluctance to do so.  This initially may be limited to a dog seeming to favor one leg over the other or simply taking a little extra time to come when called.  Gradually, symptoms worsen.  The dog may totally refuse to put any weight on a leg, walking with a permanent limp.  Some dogs may refuse to get up and walk altogether and may have to be carried to their food bowl or outside to go putty.  Other common signs include hopping instead of walking, whimpering, whining, lethargy, and a reluctance or refusal to go up stairs.

 

Although there are not as many external physical signs of hip dysplasia as behavioral ones, a few do become apparent as the condition worsens.  The most common is a narrow stance in the hip joints, causing the back legs to appear unnaturally close together.  As the dog’s behavior changes, physiological changes often follow.  Because dysplastic dogs usually use their back limbs considerably less, the muscles on the rear legs often atrophy sometimes to an extreme state.  At the same time, the front legs need to pick up the slack, and begin to do considerably more work than they would otherwise.  This leads to a very muscular shoulder and chest region.

 

DIAGNOSIS & TESTS: 

 

Diagnosis of hip dysplasia is conducted primarily for two reasons, to help relieve the pain and symptoms of an individual dog and to screen a dog that may potentially be bred to ensure that it does not pass the condition on to its offspring.  Screenings of potential parents are very useful for a condition such as hip dysplasia which often does not begin to manifest symptoms until many years after most dogs are first bred.

 

In cases where a dog has begun to display symptoms of hip dysplasia, veterinarians will typically take three or four stages to make a diagnosis.  To begin, the veterinarian will take into account a dog’s breed, size, age, and all of its symptoms.  Next, a complete physical exam will be conducted that will include blood work.  This blood work may indicate the presence of inflammation in the hip joint.  Although the first steps are helpful, the critical test is x-rays.  Dogs that have begun to show signs of pain and arthritis usually have a case of hip dysplasia that is so advanced that it is clearly visible on x-rays.  Many veterinarians choose to have dogs suspected of being dysplastic anaesthetized for their x-rays.  This allows them to manipulate the hips in various ways without hurting or unnerving the dog.  Such manipulations can help the vet make a diagnosis by sound and feeling, and can also aid in the x-ray process by allowing for multiple angles.

 

In cases where a dog is being screened for breeding purposes, there are two major testing methods.  The most common method is the OFA method, developed by the Orthopedic Foundation for Animals in the 1960’s.  The OFA requires that all dogs tested be at least 24 months of age and recommends that all female dogs tested not be in heat, pregnant, or nursing.  This is because canine hips are rarely fully developed until 2 years of age and the hips of female dogs naturally widen slightly as a result of reproductive cycles.  X-rays are taken of anaesthetized dogs which are then graded by three separate OFA certified radiologists.  The average score of the three radiologists is then determined and becomes the dog’s OFA grade.  There are 7 OFA grades.  Normal dogs are graded fair, good, or excellent.  If the radiologists are not able to reach a consensus the dog is labeled borderline dysplastic.  For dogs that are determined to be dysplastic, they are given a grade of mild, moderate, or severe.    The OFA will provide preliminary evaluations (performed by 1 radiologist) for dogs less than 24 months to aid in breeding purposes.  Such evaluations are reliable between 70% and 100% of the time depending on the breed.

 

In 1983, the University of Pennsylvania conceived the University of Pennsylvania Hip Improvement Program (PennHip), which became a usable system for veterinarians ten years later.  Like the OFA method, PennHip requires dogs to be anaesthetized for their x-rays.  Unlike the OFA method, the PennHip method can be used on puppies as young as 16 weeks.  During the x-rays, weights and external devices are used to manipulate the femur away from the acetabulum.  The amount that the caput moves (also known as joint laxity) is measured by using a distraction index or DI.  The PennHip DI ranges from 0 to 1 and is determined by dividing the distance the caput moves laterally from the center of the acetabulum by the radius of the femur head.  The lower the DI the less dysplastic the hip is.  As a rule, a DI of under 0.3 is considered acceptable, and the vast majority of dogs with a score of 0.3 or better do not develop osteoarthritis as a result of hip dysplasia studies have shown that PennHip scores given at 4 months are a very good indicator of future development of hip dysplasia, although scores given at 6 months and 1 year are better.  Although slightly different, PennHip and OFA achieve very similar results.  A comparison of the PennHip and OFA scores of 65 dogs found that all dogs scored as mildly, moderately, or severely dysplastic by the OFA scored higher than a 0.3 using the PennHip method.

 

CONVENTIONAL TREATMENT & MANAGEMENT: 

 

Because hip dysplasia is a hereditary condition that is an inherent part of a dog’s genetic code, it is impossible to cure entirely.  However, there are numerous treatments available to alleviate the condition’s symptoms and the pain that it can inflict.  There are currently thousands of different treatments currently available for hip dysplasia, and new ones are being developed constantly.

 

The treatment options selected for each individual case of hip dysplasia will vary tremendously depending on the individual circumstances of that case.  The first step is often to reduce or eliminate any factors which may be exacerbating the problem.  In cases of overweight dogs, it is very important that the dog’s weight be brought under control in a manner that will not cause it even more pain.  Exercise routines may need to be changed to ensure that the dog is in as little pain afterwards as possible.  Diets may need to be modified as well.  Dysplastic dogs should be kept warm at all times and should always be provided a proper place to sleep.  Special accommodations should be provided whenever possible, such as ramps which allow a dog to walk onto a bed or into a car instead of jumping into them.

 

The next step is to attempt to alleviate the dog’s suffering by non-surgical remedies.  Most vets will prescribe one or several anti-inflammatories.  Such drugs will hopefully reduce swelling and inflammation in the joint and therefore reduce the dog’s pain.  Among the most commonly prescribed are carprofin, etodolac, deracoxib, firocoxib, tepoxalin, meloxicam, buffered aspirin, and corticosteroids.  In addition to these medications, veterinarians usually recommend an assorted of vitamins and other supplements.  In certain cases, massage and physical therapy are beneficial as well.  In recent years, a number of injections have become popular in fighting the osteoarthritis caused by hip dysplasia.  Every injection will have a slightly different impact.  Two of the most popular are polsulfurated glycosaminoglycan, which helps prevent cartilage breakdown and aids in cartilage production, and hyaluronic acid, which increases the viscosity of the joint fluid.  For dogs which are in severe pain, many veterinarians will provide stronger pain killers, although caution is always necessary for their use.

 

Sometimes, a dog will not respond to any of the non-surgical treatments available for hip dysplasia, leaving surgery as the only option.  Because the surgical options available for hip dysplasia are all very major surgeries and quite expensive, veterinarians are loathe to use them unless absolutely necessary.  A number of factors will help determine whether surgery is a viable option including the age of the dog, risk factors such as potentially complicating conditions, cost of the surgery, and the degree of pain and discomfort experienced by the dog.  There are a variety of hip dysplasia surgeries available for older dogs, but two have become the most common.  For dogs less than 40 pounds, sometimes femoral head and neck excision are possible.  This surgery does not replace the entire joint, but rather the caput and neighboring parts of the femur.  During this surgery, the caput is removed and replaced with a fibrous pseudo-joint made either out of natural scar tissue or artificial materials.  Femoral head and neck excision is primarily used only in cases where total hip replacement is not feasible due to other medical conditions or cost.  This procedure is very useful in reducing pain and discomfort, but usually results in a loss of full movement and joint stability.  For adult dogs which are not suitable for femoral head and neck excision, total hip replacement is usually the best option.  Total hip replacement can now be performed on any dog regardless of size, although certain medical conditions may make it impossible.  Dogs undergoing total hip replacement have the entire hip joint removed during surgery and replaced with an artificial prosthesis.  If a dog requires both joints to be replaced, a wait time of three months is usually necessary in between surgeries.  Total hip replacement is a very major surgery, but it has very good results.  Most dogs eventually return to a normal level of activity free of pain.

 

In recent years, preventative hip dysplasia surgery performed on puppies has become increasingly common.  These surgeries are designed to correct joint problems before they lead to long term pain and suffering.  Two such procedures are most common.  Juvenile pubic symphysiodesis is the less invasive of the two options.  This surgery fuses the two pelvic bones together earlier than they would naturally, allowing the other parts of the hip to develop naturally.  Unfortunately, this procedure can only be performed prior to an age of 20 weeks (preferably 16) meaning that very early diagnosis is a necessity.  For dogs less than 10 or 11 months old, triple pelvic osteotomy is also an option.  In this surgery, the pelvic bones are surgically broken and the caput and acetabulum are realigned.  Although both of these surgeries are somewhat risky and quite expensive, they have been shown to have very good results in preventing the development of serious hip dysplasia.

 

POTENTIAL COMPLICATIONS: 

 

There are numerous very serious complications from hip dysplasia.  The most common complication is osteoarthritis, which is eventually seen in the vast, vast majority of hip dysplasia cases.  Osteoarthritis causes chronic pain, which is often very severe.  As the dog’s pain level increases, it begins to move in a progressively unnatural way.  Regularly moving in a way that the body is not supposed to results in a number of skeletal and muscular problems if done over a long period of time.  The muscles in the back legs often deteriorate due to lack of use, substantially weakening them.  Dogs which routinely hop instead of walking often do long term damage to the joints in their limbs.  Many dogs develop spinal problems as well, especially in the vertebrae closest to the hips.  These problems can range anywhere from mild arthritis to crippling injuries such as slipped discs.  One of the greatest problems with hip dysplasia is that many of the complications further exacerbate the problem.  For example, dogs experiencing joint pain in addition to hip dysplasia will often become even more inactive and gain even more weight, which increases the strain on the joints and the pain the dog experiences.

 

There are also a large number of complications from the various treatment options for hip dysplasia.  There are always potential side effects from any medicine, pill, or supplement, especially if a dog is taking multiple products.  Veterinarians should be carefully consulted over any side effects present in each individual medication and the combination of multiple medications.  Surgery is also inherently risky.  This risk is greatly heightened for hip dysplasia surgeries, which are incredibly invasive and major.  Many dogs are sensitive or allergic to anesthesia and may experience difficulty breathing, heart palpitations, anabolic shock, or even death when put under.  There is also always the possibility that the dog will bleed to death on the operating table, especially if the dog has an undiagnosed blood disorder such as Von Willebrand’s disease.  Even the most careful and skilled surgeon may cause unanticipated damage to another part of the dog’s body during surgery.  Because hip dysplasia surgery comes close to many other parts of the body such as the spine, lower digestive tract, and limbs, there are nearly endless possibilities for damage.  Although rare, it is also possible for hip dysplasia surgery to worsen a dog’s condition because it is often difficult to anticipate how an individual dog may recover.

 

HOLISTIC REMEDIES: 

 

Because hip dysplasia is caused largely by a genetic defect in the dog’s skeletal structure from birth, holistic remedies are incapable of curing the condition.  The only way to “fix” the structural problems responsible for hip dysplasia is with corrective surgery, surgery that is not possible with holistic medicine.  However, there are a very large number of holistic treatments available to treat the many symptoms of hip dysplasia, especially the pain it causes.  Many of these remedies may substantially reduce a dog’s suffering, and may even make it possible to delay corrective surgery, in some cases permanently.  Always remember to consult with a veterinarian before using any holistic remedies, especially if the dog is already taking regular conventional medications, to avoid possibly dangerous side effects.

 

Some of the holistic remedies prescribed to treat hip dysplasia are thought to protect and strengthen cartilage and other connective tissue such as ligaments and even to stimulate their growth and repair.  Among the most common include perna mussels (Perna canaliculus), avocado, soybean, glucosamine, chondroitin,  Duralactin, and the sulfurous compound methyl-sulfonyl methane (MSM).  A vast array of anti-inflammatory and pain-relief options is also available.  Some of the most common include S-Adenosyl-L-methione (SAMe, Denosyl SD4), omega-3 fatty acids, Rosemary (Rosmarinus officinalus), and Meadow Sweet (Filipendula ulmaria).  In recent years, physical treatments have also become increasingly popular to treat hip dysplasia holistically.  Regular massage and acupuncture are thought to greatly reduce a dog’s pain, especially for the short-term.

 

 

Hip dysplasia is an inherited disease in dogs that is characterized by abnormal development of the acetabulum and head of the femur. It is more common in large breeds