Knowledge about osteoarthritis (OA) in cats - prevalence, impact on lifestyle, efficacy of therapy - is less well developed than for the dog. Since cats have a small body size, and are light and agile, they compensate for orthopedic diseases better than dogs. Cats are also notorious for hiding signs of illness, especially if onset is insidious, and it is more difficult to interpret signs of pain or discomfort. In recent years, several excellent reviews of OA in the cat have been published.
Signalment and Clinical Signs
The most commonly affected joints are the elbow and hip, but other joints such as the lower spine and stifles may also be affected. Most cats will have bilateral joint involvement. The average age of cats with OA in various studies is typically over 10 years.
Clinical signs associated with OA in cats include:
2. Reduced activity, difficulty with jumping or stairs
3. Anorexia, weight loss
4. Irritability, aggression
5. Restricted ability to do normal activities
6. Inappropriate elimination and constipation
7. Decreased grooming
8. Lameness or stiff gait
9. Alopecia over affected joints
The diagnostic approach to that in dogs although the clinical presentation in cats is different. A medical history, physical examination, and radiographs are most commonly employed. Further diagnostic steps might include joint fluid analysis and culture, arthroscopy, myelography, or advanced imaging such as magnetic resonance imaging (MRI) or computed tomography (CT).
When taking a medical history, especially for senior cats, questions should be focused on changes in activity and behavior, rather than solely on lameness. Owners of cats with OA typically report changes in gait, jumping, use of stairs, agility, grooming, posture, and overall level of activity. Many signs of chronic pain are not obvious to owners, or may be misinterpreted as due to aging. Validated questionnaires to assess quality of life in cats, the relationship to OA, as well as assessment of response to treatment, are in development.
Radiographic signs of OA in cats are variable and several studies have reported a mismatch between radiographic and orthopedic exam findings in cats. In one study of feline cadavers, the joints most likely to have cartilage damage without radiographic evidence of OA were the stifle, coxofemoral joint, elbow, and tarsal joint. Radiographs are best at demonstrating bony changes and changes in the cartilage and synovium are not well demonstrated on plain radiographs. Joint effusions and joint capsule thickening are rarely evident. Typical bony changes include osteophyte development, subchondral sclerosis, perichondral bone erosion and change in congruity of articular surfaces. Soft tissue swelling around the joint may be present. Lumbosacral OA may be indicated by collapse of the L7-S1 disk space, sclerosis of the L7-S1 endplates, and spondylosis deformans.
The goals of treatment for cats with OA include reduction of pain and inflammation, improvement in joint function, and slowing the disease process if possible. Treatments fall into four broad categories:
1. Weight loss
2. Drug therapy
Weight loss is indicated if the patient is overweight or obese and will reduce forces on the joint surfaces. Weight loss may also lead to decreased dose or frequency of drug administration. Drug therapy is indicated to control inflammation, provide pain relief, and improve function. The most commonly used drugs for OA in cats are the nonsteroidal anti-inflammatories (NSAIDs). The key to safe long-term NSAID use in cats is to use the smallest effective dose and to avoid, or used decreased doses and dosing intervals, in cats with concurrent diseases such as chronic kidney disease. It may be helpful to recommend that cats taking NSAIDs be fed only or primarily canned foods as this increases water consumption and may help avoid subclinical dehydration in predisposed patients. Guidelines for the long-term use of NSAIDs in cats have recently been published.
Analgesics can be very useful in the treatment of feline OA and may be added to other therapies. Commonly used analgesics include buprenorphine (0.01–0.03 mg/kg BID-TID, via buccal mucosa), gabapentin (starting dose 5–10 mg/kg BID-TID, PO), and tramadol (2 mg/kg BID, PO). One study of long-term use of gabapentin as an adjunct drug in 3 cats with chronic pain (average dose 6.5 mg/kg BID) concluded that satisfactory pain management was achieved.
Polysulfated glycosaminoglycan (Adequan) is said to have both chondroprotection and chondrostimulation properties. The results of clinical studies in other species are conflicting and no long-term data exists for cats. Many protocols exist for administering Adequan to cats, such as 5 mg/kg SQ twice weekly for 4 weeks, then once weekly for 4 weeks, then once monthly.
The best evaluated nutraceutical is glucosamine hydrochloride/chondroitin sulfate (Cosequin; Nutramax Laboratories). Some studies have shown relief of clinical signs of OA in dogs, horses, and people. Results of trials suggest a cartilage-sparing or chondroprotective effect for glucosamine/chondroitin via a reduction in histologic severity of OA lesions. No published studies have evaluated safety or efficacy of glucosamine/chondroitin for long-term therapy of OA in cats. Finally, therapeutic diets for arthritis in cats have become that contain omega-3 fatty acids (EPA, DHA) as well as glucosamine and chondroitin. Some data has been published indicating these diets may have beneficial effects in cats with arthritis such as improved mobility and decreased pain.
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