Definition of Arthritis in Cats
Arthritis, also sometimes referred to as degenerative joint disease (DJD) or osteoarthritis (OA), refers to the inflammation and weakening of one or more joints. It can be caused by a number of things, such as trauma, physical abnormalities, joint infections, genetic predispositions and immune system problems. Arthritis is painful, slowly progressive and almost always permanent. It can contribute to stiffness, pain, lameness, joint deformities and loss of normal function, depending on the number and location of joints involved and the age and general health of the affected animal. Arthritis is less common and usually milder in cats than in dogs. Fortunately, there are several things that owners can do to help arthritic cats (and dogs) lead full and fairly pain-free lives, including weight management, dietary and lifestyle changes, surgical procedures and use of various approved medications and supplements.
Causes of Feline Arthritis
Arthritis refers to inflammation of one or more joints. It can be degenerative or inflammatory, and each of these general categories involves several sub-categories or types. The nomenclature can be confusing, because all arthritis involves some degree of inflammation. However, the primary cause of “degenerative” arthritis is not inflammation, while the main cause of “inflammatory” arthritis is. Regardless of cause or type, the end results of arthritis are the same: moderate to crippling pain and loss of normal joint function. Here’s a general overview of arthritis in cats.
- I. Degenerative (noninflammatory) Arthritis. Degenerative or noninflammatory arthritis, also called degenerative joint disease (DJD) and osteoarthritis (OA), is the most common type of arthritis in domestic cats. It’s an inevitably progressive and irreversible disease of slow joint and cartilage deterioration.
- A. Primary. Primary degenerative arthritis is uncommon in cats.
- B. Secondary. Most of the time, degenerative feline arthritis develops secondary to another inciting event or condition, such as acute or chronic trauma, which interferes with the biomechanical forces on affected joints. Physical injury – especially to the cartilage that connects joint bones (articular cartilage) - causes chemicals called inflammatory mediators to be released. These substances break down the connective cartilage matrix faster than it can be rebuilt, which leads to joint degeneration and lots of pain. The events that trigger the release of these chemicals typically fall into one of two categories: 1) abnormal forces on normal joints; or 2) normal forces on abnormal joints. Degeneration and collapse of the joint space damages the joint’s mechanical integrity and causes bone remodeling. As the joint breaks down, bony outgrowths form, intensifying the cat’s discomfort.
- 1. Abnormal forces on normal joints can be caused by sprains, fractures, obesity, aging, poor nutrition, trauma and many other things.
- 2. Normal forces on abnormal joints can be caused by elbow and hip dysplasia, osteochondrosis dissecans, patellar luxation, ununited anchoneal process, fragmented coronoid process, cranial cruciate ligament rupture and other congenital or genetic conformational defects.
- II. Inflammatory Arthritis. Inflammatory arthritis, also called inflammatory joint disease, can be infectious or noninfectious.
- A. Infectious. Infectious inflammatory arthritis is caused by bacteria, fungi, viruses, rickettsia or other microscopic organisms. Tick-borne diseases, like Rocky Mountain Spotted Fever, Lyme Disease and Ehrlichiosis, can contribute to infectious arthritis. Bacterial joint infections can be innocuated by injections, joint taps, surgical procedures, animal or reptile bites and other open or penetrating wounds. Fungal, viral and rickettsial causes of infectious arthritis are uncommon in cats.
- B. Noninfectious. Noninfectious inflammatory arthritis usually involves the immune system and affects multiple joints. For some reason, the cat’s immune system attacks its own cartilage and joints.
- 1. Erosive. Noninfectious arthritis can erode joints and cartilage, causing severe leg and paw deformities. Rheumatoid arthritis, plasmacytic-lymphocytic synovitis and systemic lupus erythematosus can contribute to erosive noninfectious arthritis.
- 2. Nonerosive. Noninfectious arthritis can also cause inflammation and pain without eroding joint and cartilage tissue. This isn’t common in cats.
Preventing Arthritis
Feline arthritis is hard to prevent. The progression of degenerative arthritis can be delayed if the cause is resolved. Weight management is probably the most important factor. Obese cats should be on a calorie-restricted diet under veterinary supervision. Supplements can help manage arthritis pain and may delay joint damage. Affected cats should always have a comfortable sleeping area that doesn’t require excessive jumping to reach.
Initial Examination
Arthritis – especially the degenerative form of this inflammatory joint disease – is fairly common in domestic cats. Fortunately, arthritis is not particularly difficult to diagnose. In most cases, owners bring their aging cats to a veterinarian because they have noticed that they are stiff, reluctant to rise and are just generally starting to slow down. They may have problems jumping up onto furniture, grooming themselves or getting into and out of the litter box. The doctor will ask the owner about the cat’s general health, when its current symptoms started and whether they have waxed and waned, stayed about the same or steadily gotten worse. After taking a thorough history, the veterinarian will carefully examine the cat, paying particular attention to its limbs, back and joints. She will be looking for swelling, heat and signs of discomfort. A complete physical examination will help to localize the site of the joint inflammation. Usually, the cat’s history, presenting symptoms and physical examination results will point to a tentative diagnosis of arthritis.
Diagnostic Procedures
After the history and physical examination are completed, the typical initial data base for aging feline patients includes taking blood and urine samples and submitting them to a laboratory for blood work and a urinalysis. These routine tests usually don’t provide much diagnostic information about the overall condition of cats with arthritis or the causes of their discomfort, although they can help rule out other possible causes, such as joint infections, and may provide valuable information about the cat’s geriatric baseline health. Radiographs, commonly called X-rays, are a very effective tool for identifying and assessing the degree of arthritis; they can show changes in the joint capsules, soft tissue thickening and mineralization, narrowing of joint spaces, joint effusion (fluid build-up), changes in the cartilage that connects bones in joints, other bony changes, intra-articular calcified bodies (osteophytes) and other physical changes that are known to be associated with this disease. Unfortunately, the degree of abnormalities that can be seen on radiographs does not necessarily correlate to the severity of the cat’s clinical disease or to how poorly it feels. Another procedure, called bone nuclear scintigraphy, can help the veterinarian localize arthritic sites. Sampling and analysis of synovial fluid, which is the fluid lining and lubricating the inside of the joint capsule, can help determine the degree of inflammation and whether the joints are infected. Magnetic resonance imaging (MRI) and computed tomography (CT) are also available in specialized referral clinics and veterinary teaching hospitals to visualize joint incongruity, physical cartilage changes and the overall extent of the cat’s arthritis.
Special Notes
Arthritis in cats is almost always progressive and irreversible. Fortunately, there are a number of ways to manage this condition and help most affected animals maintain a good and relatively pain-free quality of life.
Effects of Arthritis – From the Cat’s Point of View
Arthritis is a painful, progressive, usually permanent joint disease that unfortunately is fairly common in companion cats. While it is most frequently seen in older, obese cats, arthritis can also strike younger animals, especially those with a genetic predisposition to developing the disease. Arthritic cats experience varying degrees of stiffness, soreness, lameness and pain in one or more of their inflamed joints. They feel worse when they get up in the morning or try to stand after taking a nap. Cold, damp weather can increase their discomfort. Because arthritis is almost always irreversible, most arthritic cats get more painful over time. In severe cases, this condition can become debilitating and even crippling.
Symptoms of Arthritis – What the Cat’s Owner May See
The symptoms of feline arthritis usually appear gradually and worsen slowly over time. Outward signs of arthritis are not specific to this disease and can mimic those of many other disorders. The first signs are often so mild that even the most observant owners may miss them. Eventually, most owners of arthritic cats will notice that their companion isn’t acting or feeling right. The signs of arthritis include:
- Intermittent lameness (less common in cats than dogs)
Cats at Increased Risk
There is no breed or gender predisposition that increases a cat’s chance of developing arthritis, although it most commonly affects aging animals. In fact, degenerative arthritis reportedly affects roughly 90% of cats over 12 years of age. Free-roaming outdoor cats have a greater risk of traumatic injuries that can contribute to arthritis, and obese cats definitely are predisposed. Genetics are thought to be influential as well.
Goals of Treating Feline Arthritis
The goals of treating arthritis are to relieve pain and inflammation, improve mechanical joint function, slow progression of the disease and stimulate the body’s ability to repair affected joints.
Surgical and non-surgical options are available to help manage arthritis, both of which can dramatically improve a cat’s comfort and quality of life. Surgery is usually a last resort, because it can be painful and exacerbate other symptoms that are already associated with the disorder.
Non-surgical treatment options include:
Administration of:
- Nonsteroidal anti-inflammatory medications (NSAIDs), to reduce inflammation and pain
- Chondroprotective agents, to promote heathy cartilage repair (polysulfated glycosaminoglycans, glucosamine, chondroitin sulfate, hyaluronan, Vitamin C, omega 3 and 6 fatty acids and MSM, among others)
- Opioids, to relieve pain
In many cases, dietary modification and weight loss alone will decrease the discomfort associated with arthritis, since obese arthritic cats tend to suffer more than fit ones. Moderate exercise can stimulate cartilage repair an help delay joint degeneration and muscle atrophy. Physical therapy, including hydrotherapy (water exercises) and passive flexion and extension of affected limbs, can be incorporated into long-term management of arthritis, although most cats resist hydrotherapy fairly strenuously. Less traditional techniques may or may not benefit arthritic cats by helping to ease pain, increase circulation, speed healing and promote wellness, comfort and relaxation. These include: massage therapy to stimulate blood flow and reduce stress, acupuncture, acupressure, chiropractic adjustment, and use of herbal or other non-regulated supplements (“homeopathic remedies”). Many of these adjunct remedies have not been scientifically studied in a well-controlled manner to assess their benefit to arthritic cats. Chiropractic manipulation of animals with musculoskeletal abnormalities is highly controversial.
Surgical treatment options include:
When a cat’s joints have become so severely damaged that non-surgical treatment options don’t resolve its discomfort, surgical options may be considered.
- Arthroscopy is the most minimally-invasive surgery currently available for arthritic animals and can be used to repair damaged shoulders, elbows, stifles (knees) and ankle joints. The surgeon makes small cuts over the joint and inserts tiny cameras to assess joint damage and plan surgical repair, which may also be done through the incisions with specialized instruments.
- Elbow and hip replacements may be available for cats at specialized hospitals, although they are rarely done. These surgeries are expensive and require a long recovery time (approximately 2-3 months).
- Damaged wrist, toe, limb and spine joints can be fused surgically using metal implants.
Prognosis for Cats with Arthritis
Although arthritis is progressive and irreversible, non-surgical and surgical therapies often help affected cats live a fairly normal life. The prognosis for cats with arthritis really depends on its cause. If the condition is caught early and is not exacerbated by age or obesity, the prognosis is usually excellent. Overweight and old arthritic cats are not good surgical candidates. Arthritis caused by immune or inherited conditions tends to worsen with time, although medical and life style modifications certainly still can enhance the cat’s quality of life. A veterinarian is the best one to give owners an idea of what they can expect from the various management options.
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