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Preventing osteoarthritis: What are the facts? (Proceedings)

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Apr 01, 2008

Osteoarthritis affects diarthrodial joints of small animals including the shoulder, elbow, carpus, hip, stifle, tarsus, and spinal articulations. Once begun, the progression of the disease can only be slowed but never completely stopped.

One of the most common joints affected in both dogs and cats is the hip. Hip dysplasia is a genetic disease and dogs with it have increased incidence of disease in other joints. Expression of this genetic trait requires many genes to act in concert and the "right environment" while the animal is developing. To date, breeding programs have been able to reduce the incidence of hip dysplasia but not to eliminate it, likely because there are so many genes and other factors involved. Breeding programs aimed at reducing the incidence of hip dysplasia would benefit from the use of the dorsolateral subluxation score. This is a method of radiographing a dog's hips in a close to weight-bearing manner to simulate the joint laxity that would occur if a dog were standing. For detecting hip laxity in dogs as young as 8 months of age, this technique has reasonable sensitivity and specificity that may be better than orthopedic foundation for animals score or the Penn Hip distraction index. Until genetic markers are available, screening such as this is the only method available, and unfortunately, will not completely eliminate the disease in some breeds of dogs. Prevention through controlling the environment is the only other option for decreasing the incidence of hip dysplasia and osteoarthritis in other joints.

A recessive mode of inheritance has been identified in the Newfoundland for cranial cruciate ligament disease. Expression of CCL disease in Newfoundlands requires two copies of the mutant allele and an environment for expression of the disease as well. Therefore, only 51% of Newfoundlands with two mutant alleles for the gene actually develop a ruptured cruciate ligament. If we control environmental factors such as body condition score, housing conditions, neutering status, diet, etcetera, we can prevent rupture in dogs; even those with a genetic predisposition. This in turn could prevent secondary osteoarthritis in these dogs.

The options for preventing osteoarthritis then falls into several categories including diet, exercise or lifestyle, and nutraceutical supplementation.

Manipulation of the diet is available to pet owners as a method of prevention but requires strict adherence and compliance. Dogs of the same litter fed 25% less than ad libidum develop osteoarthritis in hip joints 50% less often than their free-fed littermates. These same dogs had 30% decrease in the incidence of shoulder osteoarthritis. In addition these dogs had a decrease in severity of, but not incidence of, elbow osteoarthritis. Labrador Retriever puppies from parents with hip dysplasia were also placed into two groups, either ad lib or 25% less food intake over their lifespan. The dogs fed ad lib developed radiographic signs of hip osteoarthritis at 6 years of age versus the restricted-fed dogs that developed radiographic signs at 12 years of age. Overweight dogs with hip osteoarthritis and hip pain have a significant decrease in lameness following weight reduction. Many believe that keeping dogs with osteoarthritis slightly underweight can help slow the progression and severity of osteoarthritis.

The type of activities the dog participates in can also affect the progression of osteoarthritis. Strength training can reduce the progression of osteoarthritis in human knees compared to passive range of motion exercises. Exercise can maintain muscle strength, which in turn helps stabilize the joint and slow the progression of osteoarthritis. The exercise must be controlled and continued indefinitely or the beneficial effects will not be long lasting. The appropriate exercise can decrease pain associated with mild to moderate osteoarthritis as well. By controlling the exercise, excessive force on the joint and articular cartilage is avoided while at the same time building muscle strength. Examples of controlled exercises include swimming, jogging or walking on non-slick surfaces such as grass lawns, and treadmills. Exercise to be avoided in dogs at increased risk of developing osteoarthritis include jumping, running on stairs, leaping, short fast stops after running, housing on slick surfaces, and play with other dogs that involves contact with the other dog while in motion. For example, dogs that fetch a ball can still do so after a joint injury, but the ball should be rolling slowly on the ground or stopped by the time the dog retrieves it. Rehabilitation and physical therapy exercises may also prevent further injury to injured joints.

Although the mechanism is not yet known, dogs that have undergone early sterilization (less than 5 months of age) may be at increased risk of developing hip osteoarthritis. The incidence of cranial cruciate ligament injury increases if the dog is spayed or neutered, regardless of the age of the patient when sterilization was performed.