Canine Hip Dysplasia

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Canine hip dysplasia is a developmental condition that afflicts millions of dogs worldwide, particularly larger breed dogs. It is usually seen in young, growing puppies. Dogs with hip dysplasia suffer from malformation and degeneration of the hip joints. By careful breeding and management of dogs, the painful and crippling effects of hip dysplasia could be largely prevented.

What is hip dysplasia?

The hip joint is a ball-and-socket type joint where the head of the femur (the thighbone) fits into the socket of the pelvis (the hip). Puppies with an inherited predisposition to develop hip dysplasia are born with normal hips, but as they grow, abnormal development of the skeleton and musculature means that the ball no longer fits correctly in the socket of the joint. This leads to an underlying problem of hip laxity, where the head of the femur easily becomes dislocated from the hip joint. Dogs with hip dysplasia have inflamed joints with damaged cartilage (the “cushion” of the joint) which can manifest as pain and lameness in one or both of the hind limbs.

The severity of the condition tends to decrease at 12-15 months of age as the dog matures and hip joints remodel and become more stable. Once the hip remodels, the laxity of the joint becomes less of a problem and affected dogs usually improve. Unfortunately, as these dogs reach middle-age, they tend to relapse, as arthritis of the joints commonly develops.

Why do some dogs develop hip dysplasia?

There are a number of risk factors that cause some dogs to develop hip dysplasia while other dogs have perfectly normal hips. Certain breeds inherit a genetic predisposition to develop malformed hips. The most commonly affected breeds are larger breed dogs such as the Bernese mountain dog, German shepherd, Golden Retriever, Labrador retriever, Rottweiler, and the Saint Bernard. Although smaller breed dogs (and occasionally cats) can also develop hip dysplasia, they are less likely to show signs of pain and lameness.

Environmental factors also play an important role in the development of hip dysplasia. Diet, growth rate, and exercise will modify the effects of the underlying genetic predisposition. Puppies that are fed high energy diets (e.g. diets high in fat), are over-exercised, or grow too fast are much more likely to suffer from hip problems.

What are the signs of hip dysplasia?

Sometimes there are no early signs of hip dysplasia in dogs. The signs of hip dysplasia will depend on whether one or both of the joints are affected, and how severely they are affected. Clinical signs of hip dysplasia tend to be first seen at 4-10 months of age, especially in larger breed dogs that have undergone rapid growth rate. However, some dogs may not show any signs when they are puppies and it is only in old age when they develop signs of arthritis.

What to look out for:

• Intermittent or persistent lameness (usually worse after exercise)
• Abnormal or swaying gait
• Difficulty getting up from a lying or sitting position
• Reduced activity
• Reluctance to run, jump, or climb stairs
• “Bunny-hopping” (the dog moves both hind limbs simultaneously while running)
• Poor muscle development over the hindquarters
• Unwillingness to move the affected joint (e.g. will not sit on command)

These signs can be seen in puppies with dysplastic hips and older dogs that are developing osteoarthritis. If your dog is exhibiting any of the above symptoms, do not hesitate to consult a veterinarian.

How does the veterinarian diagnose hip dysplasia?

Vets diagnose hip dysplasia based on the breed and age of the dog, its medical history, physical examination, and x-rays. During the exam, the vet may walk the dog up and down in order to study the gait and determine the affected limbs. The hip joint is also manipulated and assessed for signs of joint pain, laxity, and diminished range of motion. As manipulation of the joint is often a painful procedure, it is sometimes necessary to sedate or anesthetize the dog in order to fully examine the hip joints. Sedation is also required for x-rays, which will confirm a diagnosis of hip dysplasia. X-rays allow the veterinarian to appraise the severity of the damage to the hip joints, and to determine whether there is any secondary arthritis present.

Once a diagnosis of hip dysplasia is made, how can the condition be treated?

The treatment options for dogs with hip dysplasia are conservative medical therapy or surgery. The type of treatment option will ultimately depend on the age of the dog, the severity of disease, and financial considerations.

Many dogs will not require significant treatment as the condition often resolves at 12-15 months when the hip joint remodels and stabilizes. These dogs can usually be treated conservatively:

1. Weight/Growth Rate Control: excess dietary energy can lead to rapid skeletal growth and obesity. Puppies with excessive growth rates are not only at greater risk of developing hip dysplasia, but they will also suffer more severe dysplasia. It is important to feed a diet that minimizes any further weight gain.

2. Exercise: regular controlled exercise and/or physiotherapy will help reduce joint stiffness and build-up muscle strength. Strenuous exercise should be avoided as it may exacerbate your dog’s condition. Swimming is highly recommended as it is a low-impact activity that maintains joints mobility.

3. Pain Control: non-steroidal anti-inflammatory drugs (NSAIDs) such as meloxicam (Metacam) and carprofen (Rimadyl) are useful in minimizing pain and reducing inflammation of the joint. Because of the associated side effects (e.g. kidney damage, diarrhea, stomach ulcers), these painkillers have limited use and can only be used under veterinary prescription.

4. Supplements: cartilage-protecting supplements such as polysulfated glycosaminoglycans (PSGAGs) are becoming increasingly popular as an adjunctive therapy.

Dogs that fail to respond to conservative treatment may require surgery to repair the malformed hip joint. In younger dogs with significant lameness, the triple pelvic osteotomy (TPO) is an operation designed to halt further damage to the joint.

The TPO should slow the onset of osteoarthritis by improving the shape of the hip joint.

For older dogs that already have advanced arthritis there are a couple of surgical options. In smaller breed dogs, the femoral head excision or ostectomy is a salvage procedure for the joint which basically involves removing the head of the femur. Removing the head of the femur should eliminate the pain caused by arthritis. For medium to large breed dogs, a total hip replacement can dramatically increase a dog’s quality of life.

While these surgeries can be very successful in improving your dog’s mobility, they require a high degree of time and commitment from the owner. Dogs will require several weeks of post-operative care. Furthermore, all of the surgeries are quite expensive!

How can I prevent hip dysplasia?

As awareness about hip dysplasia in dogs is growing, more people are making the effort to prevent this crippling disease.

When purchasing a puppy from a breeder find out the hip scores of the dam and sire. Hip scores are measures of hip laxity based on x-rays taken of the dog’s hips. To find out more about hip scores, contact:

• PennHIP program (http://www.pennhip.org)

• BVA/KC hip scheme (http://www.bva.co.uk/public/chs/hip_scheme.asp) – United Kingdom.

Dam/sire breedings that result in puppies with dysplastic hips should not be repeated. If your puppy is diagnosed with hip dysplasia, it is helpful to report this to the breeder.

If you have a large breed puppy, it is particularly important to feed the correct diet (a balanced puppy diet), to provide the dog with a controlled amount of exercise, and to pick up any problems as early as possible. The earlier hip problems are diagnosed, the more successful treatment is likely to be.

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