Hip Dysplasia in Dogs

Hip dysplasia (HD) is defined as a deformity of the coxofemoral (hip) joint that developes during the growth period.  Hip dysplasia is a hereditary condition that results from a poorly fitting hip joint.  As the dog walks on this joint, arthritis will eventually develop, causing pain in the joint.  The degree of lameness that occurs is usually dependent upon the extent of arthritic changes in the hip joint.

 Contributing Factors

   Dogs suffering from HD have a genetic background, but the contributing factors are many. Two of the most important are overnutrition and excessive exercise, especially in the young puppy.

 Prevalence

   Most breeds of dogs can be affected with hip dysplasia although the resulting lameness is predominantly seen in the larger breeds of dogs, such as the German Shepherd, St. Bernard, Labrador Retriever, Pointers, and Setters.  There is equal distribution of the disease between male and female dogs.

Causes/Transmission

The causes of hip dysplasia are complex and multiple.  Environmental and genetic factors are both involved.  It is difficult, if not impossible, to pinpoint a single cause.

Clinical Signs

 The typical clinical signs of hip dysplasia are rear leg pain, incoordination, and a reluctance to rise from a lying position.  Wasting of the large muscles in the rear limbs may eventually develop.  Most owners report that the dog has had difficulty in rising for a period of weeks or months; lameness and pain subsequently develop.  Again, the severity of signs and progression of the disease usually correlate with the extent of arthritis in the joint.  Clinical signs can occur as early as 4-6 weeks of age, but most dogs manifest the disease as a lameness around one to two years of age.  Dogs with mild hip dysplasia and minimal arthritis may not become painful and lame until 6-10 years of age.

 Diagnosis

Tentative diagnosis of hip dysplasia is made on the basis of history, breed, and clinical signs.  A large breed dog that has been slow to rise for several months and is now lame is highly suspect for hip dysplasia; a dog that refuses to rise should also be considered a candidate.  Because the clinical signs may mimic other diseases, final diagnosis of hip dysplasia can only be made on the basis of specific radiographic (x-ray) findings.  To obtain the proper radiographs, dogs must be carefully positioned on the radiographic table.  This procedure requires the use of a short-acting anesthetic.  The radiographs are evaluated for abnormal shape of the hip joint and for degenerative changes (arthritis).

Treatment

 The degree of clinical signs and arthritic changes in the joints determine the specific approach to therapy. Treatment of hip dysplasia may involve weight management, the use of drugs or surgery, or all three.  The options are as follows: 

1.  Nutraceuticals: Articular cartilage plays an important role in optimal joint function. Bathed with synovial fluid, articular cartilage fulfills its primary responsibilities by providing a smooth, low friction surface between articulating bone ends while transmitting load forces to the underlying bone.

Cartilage replenishes its major components by manufacturing and remodeling prodigious amounts of collagen and proteoglycans. This constant and ongoing synthesizing process often generates extremely large demands for building blocks of collagen and proteoglycans. If the raw materials (nutrients) for these building blocks are not available in the amounts required, the synthesizing process is impaired and the cartilage loses its ability to replenish itself.  Cosequin and similar products provide the raw materials that are essential for the synthesis of synovial fluid and the complete cartilage matrix including collagen, hyaluronic acid and the various modified sugar chains of the glycosaminoglycans.

2.  Anti-inflammatory drugs.  Several drugs will give relief from pain.  Aspirin may work well in some dogs.  Other steroidal (cortisone) and more potent non-steroidal anti-inflammatory drugs may also be used.  Most have some side effects and require administration once or twice daily.  Many dogs have severe stomach irritation to ibuprofen so this drug is not recommended.  Unfortunately, it is not possible to predict which dog will respond to which drug.  Therefore, a series of trials may be needed to find the most effective one for your dog. 

Extreme caution is advised when these drugs are given to dogs with a history of kidney disease or with marginal kidney function.  Many of these drugs have an adverse effect on blood flow to the kidneys and can lead to kidney failure.  This does not appear to be a concern if kidney function is normal.  As alluded to above, dogs with a history of ulcers are also at risk for complications.  Your veterinarian can determine the risk for your dog.

 Anti-inflammatory drug therapy is most often used in older dogs, in dogs that did not get good relief from surgery, or in dogs for which surgery is not feasible.

 3.  Surgery:  There are many surgical procedures that have been used to treat hip dysplasia.  The following three are mos often recommended today.

Femoral Head Ostectomy (FHO) is another choice.  The hip joint is a ball and socket joint.  FHO is the removal of the ball part of the joint.  This gives excellent results in small dogs because a functional "false joint" forms.  However, some large dogs may not form this "false joint" as well.  This procedure is usually used in large dogs if arthritis is very severe, if the hip dislocates, or if the expense of the other procedures is considered to be prohibitive.

Triple Pelvic Osteotomy is a procedure in which the pelvis is cut in three places around the hip joint.  The bone is rotated to create better alignment with the femoral head (the ball).  It is reattached so that the joint functions in a more normal fashion without looseness and pain.  This can only be performed in a dog with no arthritic changes in the joint, with a fairly deep acetabulum (hip socket), and at an early age while the bones are still growing, usually less than 1 year of age.  It is more expensive than a FHO procedure.

Total Hip Replacement is possible, as is done in humans.  A stainless steel ball and socket are attached to the pelvis and femur in place of the abnormal ones.  It is another very expensive procedure, but it may give many years of pain-free use of the hips.  Although the intent is for the transplant to be permanent, the new joint may loosen after a period of time.

Prognosis

 The prognosis is variable depending upon the age of the dog, severity of the dysplasia, and response to medical and/or surgical intervention.

 Prevention

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.  Because the inheritance of the disease is so complicated, many questions remain regarding eradication of the disease. 

 Here are some practical suggestions: 

1. Have your dog radiographed before breeding to be sure the hips are normal.  If they are not, this dog should not be bred.

2. Consider a feeding program to slow growth.  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 dog food specially made for large-breed puppies or an adult-type 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.

3. Avoid excessive or high impact 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 it were handicapped, but long sessions of running or chasing thrown objects can be detrimental to joints.

Hip Certification

 The Orthopedic Foundation for Animals (O.F.A.) is an organization established for the purpose of standardizing the evaluation process of canine hip radiographs.  The O.F.A. consists of a board of certified veterinary radiologists who are skilled in detecting hip dysplasia.  If the radiographs submitted to the O.F.A. are declared normal, the dog is issued an O.F.A. certificate number indicating that it has normal hip confirmation.  The O.F.A. requires that dogs must be a minimum of two years of age to be certified.  Many breeders require that a dog must have an O.F.A. certificate before breeding is allowed.

 Another hip evaluation program is called the PennHip method.  Radiographs are made of the anesthetized dog in such a manner as to place outward force on the hip joints.  This can reveal looseness in the joints that may elude detection by the more standard radiographic methods.  It is also useful in identifying hip dysplasia in puppies as young as 4 months of age.  Although any veterinarian can make the appropriate radiographs and submit them for O.F.A. certification, the PennHip method must be performed by a veterinarian specifically trained and certified in this procedure.