Canine Hip Dysplasia

The hip is a ball-and-socket joint in which the rounded portion of the femoral head inserts into a socket (called the acetabulum) in the pelvic bone. When this joint functions normally, it allows a wide range of motion, as well as provides maximum body support.

Hip dysplasia is a complex disease. It was first described in the 1930s and was thought to be a rare, uncommon disease. The disease process begins early in life, and as it progresses, causes a deformation of the hip joint as well as the development of degenerative joint disease (commonly called arthritis). Abnormal hip joint laxity (looseness between the femoral head and the acetabulum) is the initiating factor that results in hip dysplasia.

Hip dysplasia can be seen in almost all breeds of dogs, although it occurs most commonly in the large and giant-breeds. It is the most common inherited joint disease of large dogs and the most important cause of arthritis in the hip.
Breeds of dogs with a high incidence of hip dysplasia include Akitas, German Shepherds, Labrador Retriever, Golden Retriever, Rottweilers, Newfoundlands, and Chow Chows.
Hip dysplasia is not caused by one single gene. It is a polygenitic, complex disease, caused by several genes. The expression of the disease, or how it affects individual animals, depends upon several factors. Altering the environment in which the puppy is raised can contribute to the severity of symptoms. Experiments have shown that low protein diets and reduced activity during the puppy stage may reduce the symptoms of hip dysplasia. In these dogs, even though symptoms may not be as severe, they still have dysplastic hips and carry the genes that contribute to the disease. Another factor that influences the symptoms of hip dysplasia is pain tolerance level. Like humans, individual dogs have different pain tolerance levels. Some dogs with mild hip dysplasia have painful hips and are severely crippled. Other dogs with similar radiographic features do not have painful hips and do not exhibit the same degree of lameness. In both situations, the dogs have dysplastic hips and should not be considered for breeding.
The only current method for reducing the occurrence of the disease is by selective breeding. Only dogs that have sound hips, with no radiographic signs of hip dysplasia, should be used for breeding. Dogs with radiographic signs of hip dysplasia should not be used for breeding and should be neutered at the appropriate age.
Radiography (X-rays) is the only method for accurately diagnosing canine hip dysplasia.
Symptoms of Hip Dysplasia
Clinical symptoms of hip dysplasia commonly begin between five to eight months of age. In some dogs, symptoms appear earlier. In other dogs, symptoms appear later in life. A small percentage of dogs with radiographic signs of hip dysplasia show no symptoms at all. Dogs that are radiographically positive for hip dysplasia that show no clinical symptoms of the disease should not be bred as they contribute their genes to their offspring.
There is a wide range of symptoms for dogs with hip dysplasia. Some animals have a slight limp, while others are severely crippled. A hind end lameness is the most common feature seen in dogs suffering from hip dysplasia.
Symptoms seen in dogs with hip dysplasia include:

• Wobbly gait—the back end appears wobbly
• Bunny-hopping gait (in the rear legs) when running
• Difficulty manipulating stairs—particularly climbing stairs.
• Difficulty rising from sleep or a sitting position—when rising, the weight is often placed on the front legs to relieve the pressure on the hips.
• Dogs often shift their weight from the back end to the front. These dogs often have well-developed muscles in the front and lack muscular development in the rear.
• Dogs with hip dysplasia often have degenerative joint disease (arthritis). Like humans, the disease is worse in the mornings and improves after mild exercise.
• All dogs with hip dysplasia do not experience severe pain. Some dogs experience little pain and you would never know that they had the disease.

Diagnosis
Since hip dysplasia can often be confused with other rear leg injuries, a complete veterinary exam (along with X-rays) is required for a diagnosis. X-rays are essential for confirming the diagnosis as well as evaluating the nature and severity of the disease.
X-rays and Hip Dysplasia
There appears to be a general misunderstanding regarding x-rays and hip dysplasia. A dog showing symptoms of hip dysplasia can be x-rayed at any age. If there is radiographic evidence of hip dysplasia, the diagnosis is for the entire life of the dog. It doesn't matter if the dog is three months or eight years old: once x-rays are taken and there are radiographic signs of hip dysplasia, the animal is labeled for the rest of his or her life. Even if the dog exhibits absolutely no symptoms of hip dysplasia (limping, etc.), if there is radiographic evidence, the animal has the disease. If used for breeding, these dogs can pass their dysplastic genes to their puppies as easily as a dog exhibiting severe symptoms of the disease. This is the rationale behind radiographing all medium and large-breed dogs before establishing a breeding program.
All puppies appear to be born with normal hips. In dogs affected with hip dysplasia, radiographic changes become evident within several months to several years. A good x-ray at a young age does not rule out the possibility of hip dysplasia occurring later in life. At 24 months, more than 95 percent of dogs with hip dysplasia show radiographic changes associated with the disease. The O.F.A. does not classify a dog's hips until he or she is at least two years old.

The Orthopedic Foundation for Animals (OFA)
For more detailed information, visit the OFA's excellent and informative website. The OFA is a private non-profit foundation. Presently, they maintain the largest data base on canine hip conformation in the world.The purpose of the OFA is twofold:

1. To provide a standardized evaluation for hip dysplasia.
2. Serve as a database for the control of hip dysplasia.

How the OFA Functions
Veterinarians who have specialty degrees in veterinary radiology evaluate all x-rays that are sent to the OFA. There are about 20-25 board certified veterinary radiologists who make up the OFA. These radiologists are located throughout the United States in both private practice and at universities. From the pool of 20-25 veterinary radiologists, three are randomly selected for each case. Each radiologist independently evaluates an animal's hip x-ray. This evaluation takes into consideration variations due to sex, age, and breed. After interpreting the x-ray, each radiologist independently assigns a rating to the hip.
Hip ratings fall into 7 classifications. These categories include:

1. Excellent
2. Good
   
3. Fair
4. Borderline
5. Mild Hip Dysplasia
6. Moderate Hip Dysplasia
   
7. Severe Hip Dysplasia
   
   

Hip grades of excellent, good, and fair are considered within the normal limits for the breed and are given OFA certificates with OFA numbers. Radiographs classified as borderline, mild, moderate, and severe hip dysplasia do not receive OFA numbers. Dogs must be at least two years old in order to receive an OFA number.

This dog was x-rayed again at two years and had normal hips.

The OFA accepts radiographs of puppies as young as four months of age for preliminary hip evaluation. These dogs do not receive an OFA number and must be radiographed again at two years of age (or later). This is often done for dog breeders who are interested in detecting puppies with hip dysplasia. If a puppy is diagnosed with hip dysplasia at a young age, the economic loss associated with training, handling, and showing is greatly reduced.
Treatment
Both medical and surgical treatments are available for dogs with hip dysplasia. Medical treatment focuses on exercise restriction, controlling body weight, and management of pain. Most cases of moderate hip dysplasia are managed this way. Swimming is an excellent form of exercise for dogs suffering from mild hip dysplasia.
Pain killers and anti-inflammatory medications are commonly used to control symptoms associated with hip dysplasia. Medications frequently used include:

• Aspirin
• Naproxen
• Adequan
• Cosequin
• Phenylbutazone
• Carprofen

Some of these drugs may cause harmful side effects. Before beginning a treatment regime, a thorough consultation with your veterinarian is required. Frequent visits to the veterinarian may be necessary in order to adjust dosages and change medications.
Surgery is generally performed on young dogs or dogs with severe cases of hip dysplasia. The decision for surgery should should be discussed in detail with your veterinarian. Surgery is expensive and often requires extensive post-surgical home care.
Presently, three surgical techniques are used for dogs with hip dysplasia. Each one is briefly described below.

1. Triple pelvic osteotomy—This surgery is almost exclusively reserved for young animals (usually aged five months to one year). Radiographs of the dog's hips cannot show any signs of degenerative joint disease (arthritis). The surgery involves rotating the acetabulum (socket portion of the hip) to a more normal position in relation to the femoral head. This changes the orientation of the hip socket.
   
   Results of the Surgery
   
   Ball is seated more deeply in socket.
   Eliminates joint laxity and corrects the abnormal conformation of the ball and socket.
   
2. Femoral head excision—This procedure eliminates the pain of hip dysplasia associated with arthritis. It is considered a salvage procedure, recommended when pain and irreversible arthritis are present. The surgery involves the removal of the femoral head (ball portion of the joint). After a period of time, scar tissue fills the area between the femur and the acetabulum. This scar tissue functions like a joint and about 70% of hip-joint functionality is restored. Femoral head excision surgery is relatively inexpensive, requires minimal post-surgical home care, and can be done at any age. The surgery works well in small and medium-size dogs (dogs weighing less than 45 lbs.).
   
3. Total hip replacement—This surgery is similar to total hip replacement in humans. The ball and socket are removed and replaced with implants. Success rates are high (95 percent) as optimal joint function is generally restored. Presently, this is the best surgical technique for correcting hip dysplasia in adult large-breed dogs. After a recuperation period, most dogs regain full, pain free hip function and live normal active lives.
   

The decision to perform surgery should not be taken lightly. Discuss the various options with your veterinarian before making your decision.
Forty years have passed since hip dysplasia was first described. Despite years of research, it is still the most common inherited joint disease of large-breed dogs.