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Arthritis In Pets

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What is Arthritis?
Dr. N.J.Hayes,DVM

Symptoms and Diagnosis | Treatment | Dictionary of Terms

Arthritis is a progressive, permanent change to the articular surface of synovial joints. It occurs for a number of reasons, but regardless of the originating cause, it becomes a self-sustaining progressive change. A number of things can start arthritis and range from joint injury, hereditary malformations, immune mediated diseases, and the wear and tear of age and obesity.

Drawing of a Normal Joint The easiest way to think of joints is as movable shock absorbers. The bone is protected by a layer or cartilage and collagen (protein) and lubricated with fluid (synovial fluid) that is thick and sticky. Damage to any of these structures causes an effect on the other structures resulting in damage. Chemical mediators such as prostaglandins can affect the inflammation and pain in a joint. The protein and sugars (glucosaminoglycans) are the building blocks of the fluid and cartilage. Loss of these weakens the joint structure.

What causes Arthritis?

Arthritis or DJD (degenerative joint disease) generally starts without inflammation, but the series of events that follow lead to inflammation and subsequent degeneration of the joint surface. A number of mediators (chemical reactions) participate in this cascade.

  • Proteases (chemicals that dissolve and destroy proteins) damage the chondrocytes (cells that make up cartilage) and cause a loss of collagen (protein matrix).
  • Collagen synthesis is altered and the collagen (protein in the joint and cartilage) is weakened.
  • The cartilage matrix is weakened by the breakdown of necessary components such as glucosaminoglycans.
  • Mediators are released that support chronic inflammation.
  • Increased inflammation causes a loss of elasticity and viscosity of the synovial (joint) fluid. This leads to friction and pain in the joint.
  • Subchondryle bone becomes damaged and inflamed. It stiffens and losses elasticity increasing the mechanical damage to the cartilage.
  • Pain fibers in the joint capsule, tendons and bone are stimulated. Chemicals such as prostaglandins, leukotrienes, substance P, and others are altered form the normal levels. This increases destruction and pain as well.

Drawing of an Arthritic Joint The results of the above cascade of events lead to permanent irreversible damage to the joint and pain. Eventually the breaks in the cartilage and the loss of the cartilage results in bone on bone contact. This will limit motion and cause increased pain resulting in a loss of function.

There are many causes of arthritis which include:

  • Genetic cases such as dysplasia of the hips or elbows, medially luxating patellas (MPL), osteochondritis dessicans (OCD), and others. Cats also have inherited orthopedic disorders.
  • Injury
  • Wear and tear from age, obesity, and extreme athleticism.

Photo of a Maine Coon CatWhat are the symptoms?

Generally, the signs of arthritis creep up slowly. The pet may sleep later, move slower, walk less far, be cranky, or fail to make it up onto the couch. In the case of cats a decrease in grooming and failure to use the litter box may also be signs. As the disease progresses, lameness, loss of muscle mass, and eventually loss of function can occur.

Risk factors for developing DJD include:Flatcoat jumping into pool

  • The breed of pet such as breeds predisposed to hip dysplasia and knee problems. Maine Coon cats for example have an increased incidence of hip dysplasia.
  • Obesity
  • Age
  • Athletics
  • Certain diseases such as Cushings, Diabetes Mellitus, and hypothyroidism

How is it diagnosed?

Some other issues must be ruled out before a diagnosis of arthritis is complete. Certain cancers, infectious diseases such as Lyme disease and Erhlichia, and immune mediated joint disease (rheumatoid arthritis and lupus) must be checked for. A combination of physical exam findings, blood work and radiographs (x-rays) and possibly joint aspiration are generally used. Other testing could include MRI and CT scans.Early Hip Dysplasia x-RayArthritis from Hip Dysplasia x-Ray

To prevent DJD one needs to manage the pet's weight. Keeping pets on the thin side can reduce or even eliminate the risk of DJD. Supplements that provide the building blocks for collagen and joint fluid and well as decreasing the inflammatory mediators are also of value. In some cases, interceptive surgery may be needed and can be very helpful. Examples of this are repair of fractured coronoid process in elbow dysplasia and various surgical techniques to manage hip dysplasia.

How is Arthritis treated?

Treatment of arthritis employs many angles. The most important step is weight loss. A loss of 10 percent of weight in obese pets can result in 100 percent improvement. One study found that weight loss alone could improve force plate measurements in pets as much as NSAIDs (pain relievers). Physical therapy such as low impact walks, swimming and passive range of motion is also helpful. On days when the pet is sore, heat applied to the joint can bring some relief, although in an acute lameness cold is often more helpful. Supplements such as Omega 3 and 6 fatty acids, glucosamine, chondroitin, and ASU are very beneficial. They increase joint fluid and cartilage health and decrease inflammatory mediators in the joints. NSAIDS (non-steroidal anti-inflammatory drugs) such as Rimadyl, Deramaxx, and Meloxicam, help reduce pain and inflammation. Aspirin unfortunately will reduce pain, but studies have shown that increased destruction may occur. Chondro-protective drugs such as Adequan may help some patients, but care must be taken not to use them with NSAIDs. The last resort drug is often steroids. Steroids are not a pain reliever, but do dramatically reduce inflammation and can help dogs and cats feel much better. They however, should not be given with NSAIDs.

PoohArthritis can be a debilitating disease in pets, but fortunately we have many ways to aid in the comfort of our pets giving them an increased quality of life. If you have any questions, or if we have recommended further testing, please feel free to contact us at:
Whitney Veterinary Hospital or Whitney Cat Care Clinic, 309-685-4707.

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