Overview of Feline Arthritis
Degenerative joint disease (DJD), or arthritis, affects cats way more than previously known. One study found that 33.9% of cats aged 6 ½ years had radiographic evidence of arthritis. The prevalence of arthritis in cats increases significantly with age. The most commonly affected joints in this study were the hips and elbows.
In another study (2002), 90% of cats over 12 years of age had evidence of arthritis, most often occurring in the hips, shoulders, elbows, knees and ankles.
Degenerative joint disease (DJD), or arthritis, affects the smooth articular cartilage of the joint, which is the covering of bone in the joints that is responsible for the smooth, non-painful motion of joints. When it becomes worn, raw bone surfaces become exposed and rub together. DJD is the result, causing pain and lack of joint mobility.
DJD can occur over a lifetime of wear or as a result of injury. The soft tissue lining of the joint (synovium) is the first tissue in many animals to be affected in the disease and the subsequent irritation of the joint lining (synovitis) liberates chemical mediators that have been shown to be responsible for cartilage degeneration.
Primary cartilage damage can also initiate a cascade of events that result in further cartilage damage and synovial lining inflammation. This results in a vicious cycle of cartilage degeneration, release of degenerative factors and continued cartilage degeneration.
Normal cartilage is composed of cartilage cells (chondrocytes) and a supporting substance (matrix) that is produced by the cells. DJD involves the derangement of chondrocyte metabolism and subsequent matrix alteration.
What to Watch For
Diagnosis of Arthritis in Cats
Diagnostic tests are needed to recognize DJD and exclude other diseases. Tests may include:
Treatment of Arthritis in Cats
Treatment for DJD may include one or more of the following:
Home Care and Prevention
After your cat’s surgery, follow your veterinarian’s specific instruction concerning medications, care and recheck examinations. Limited range of motion and physical therapy exercises are usually beneficial.
Since some of the developmental orthopedic conditions that result in DJD have some component of inheritability, selective breeding of unaffected animals will help decrease the incidence of the disease in the population as a whole. This can decrease the incidence of many of the congenital orthopedic problems.
Proper nutrition is also important in order to have a normal weight gain during development.
In-depth Information on Arthritis in Cats
It has been estimated that as much as 20 percent of the feline population over one year of age has DJD. The unifying theme in DJD is degeneration and destruction of articular cartilage – the cartilage looses its elasticity and softening occurs. Fissures can form and result in fibrillation and cell death. The altered chondrocytes release mediators (enzymes and other factors) that cause the cartilage to break itself down in a vicious cycle of degeneration.
The importance of the anatomy and disease process of DJD becomes meaningful when discussing the action of many of the newer drug therapies. Normal articular cartilage covers the bone on both sides of a joint and provides nearly friction-free motion of the joint. It also provides a “shock absorbing” protection to the joint and associated bones. When the articular cartilage structure is altered, the biomechanical properties of the joint change.
Normal articular cartilage is made up of cartilage cells (chondrocytes), an extracellular matrix and water. The chondrocytes manufacturer much of the extracellular matrix. The matrix is made up of microscopic fibers called collagen, which provides a structural support for the cartilage matrix and a complex biochemical “goo” called proteoglycan. The chemical chondroitin sulfate makes up much of the proteoglycan.
The tissue surrounding the joint is called the joint capsule and it contains a thick fluid (hyaluronic acid) that is partly responsible for joint lubrication. The joint capsule becomes inflamed with DJD and the quality of the joint fluid decreases, which causes more changes to the cartilage.
There are a number of congenital orthopedic diseases that occur in the cat that can lead to DJD at an early age. Many of these are related to the osteochondrosis syndrome: