Feline Arthritis- Part 1
For many years, osteoarthritis (OA) has been an overlooked area of feline medicine. This has probably occurred for several reasons – recognition of the condition is more difficult, signs of arthritis, such as a stiff gait, are often considered to be ‘normal’ for aged cats and treatment options to help affected cats have been very limited. Fortunately over the last decade there have been great advances in feline pain recognition and treatment options provoking an increased interest in this subject.
Degenerative joint disease is the general term used to describe degenerative arthropathies affecting any joint. OA, the focus for this article, is the term used to describe degenerative joint disease affecting synovial joints and is characterized by degeneration of the articular cartilage, hypertrophy of the bone at the articular margins and changes in the synovial membranes. OA needs to be differentiated from other causes of musculoskeletal and locomotor problems (Table 1).
Causes of OA in cats include:
•Primary joint disease: this is uncommon but includes infectious and immune-mediated causes
•Secondary joint disease – for example:
-Congenital and developmental problems
-Prior trauma resulting in joint instability
-Low grade chronic ‘wear and tear’ damage to the joint(s)
The elbows, stifles and hips (Figures 1, 2 and 3) have been most frequently affected by OA and this is often a bilateral condition. The true prevalence of feline OA is not known – published retrospective studies have shown very variable figures. Studies concentrating on older cats have yielded the highest prevalence rates – for example up to 90% of cats over 12 years of age (1-3).
Clinical recognition of feline OA is very difficult and presenting signs and clinical findings do differ from those commonly seen in canine OA. It is becoming more and more apparent that the owner is the key to recognition of likely cases of feline OA and the veterinarian needs to be asking the correct questions to identify this.
A major challenge in this area of feline practice is the necessity for owner education in clinical signs to look for as indicators of OA. There should be a greater awareness of the treatment and management options which are now available and can help their cat. Many owners feel that there is little point in telling their veterinarian that their cat is stiff or less able to jump since they interpret these as normal age-related changes and they do not feel that there is likely to be any treatment available. Veterinarians also need to be more aware of the different presenting signs of these cases compared to dogs and hence a greater need for owner targeted history questions (Table 2) to highlight cases that may benefit from further assessment and treatment.
This is probably the most important diagnostic step in cats affected by OA. The signalment of affected cats is typically the middle-aged to older cat with no male/female bias reported. However there are specific causes of OA in younger cats such as congenital disorders (e.g. hip dysplasia – more common in certain breeds such as Maine Coon cats) and following trauma to bones, joints and tendons. As with dogs, obesity increases the strain on joints and can be a contributory factor to mobility problems and progression of OA.
Cats are notoriously good at masking signs of illness and not showing clinical signs – affected individuals adjust their lifestyle by becoming less active, changing sleeping positions (for example no longer sleeping in locations which require them to jump up). Other findings may include indoor toileting changes such as failing to use a litter tray, no longer using the cat flap or passing feces beside, rather than in, the litter tray. Many of these ‘lifestyle’ changes which accompany OA are often viewed as ‘normal’ in older cats and owners are unlikely to know their potential significance. In addition, many owners feel that it is normal for older cats to exercise less/be more inactive and even when they recognize signs of OA, such as stiffness, often interpret these as ‘normal’ age-related changes which are not necessarily an indicator that their cat is in pain or that it needs veterinary treatment. Behavioral changes which may also be seen include vocalization, becoming more withdrawn/reclusive and/or more aggressive with people and other animals.
Table 2 lists questions which should be asked to identify gait abnormalities, previous injuries, and behavioral/lifestyle changes which could be consistent with the possibility of a painful mobility problem. Hopefully, over the coming years, these questions will continue to be expanded and refined. Questions should be asked carefully to establish whether certain activities can be performed at all and whether this involves difficulty or reluctance. In addition, the medical history is essential in identifying other indicators of systemic illness which may affect treatment possibilities, be responsible for some of the clinical signs (e.g. vocalizing is common with hyperthyroidism) and require specific management themselves. Common examples in older cats would include renal disease, hyperthyroidism, diabetes mellitus, systemic hypertension and gastrointestinal neoplasia.
A thorough general and orthopedic examination is indicated in all cats presented. In cats greater than 8 years of age this should include palpation for a thyroid goiter, blood pressure measurement (ideally using a Doppler machine), detailed examination of the eyes for evidence of systemic hypertension, cardiac auscultation (e.g. heart murmurs common in hyperthyroid and hypertensive cats) and careful abdominal palpation for bowel masses. Cats affected by OA (Figure 4) may show reduced grooming activity manifested as a scurfy or matted coat, overgrown claws as a result of less exercise and scratching activity, and their pain may make them more resentful of general handling and movement.
Orthopedic examination is notoriously difficult in cats and a busy and stressful practice environment adds to this. Many cats will ‘freeze’ in the consulting room or only walk with a low, crouching gait to the nearest corner. Where possible, gait examination should be performed with the cat unstressed before the start of the physical examination. Allowing the cat time to relax and acclimatize to the consulting room is helpful, where possible. Alternatively, some covert observation of the cat (e.g. through a consulting room window/door) may be helpful. The cat should be encouraged to jump on/off chairs etc. to allow assessment of these activities. Owner-provided video evidence can also be useful if the cat is reluctant to walk whilst in the consulting room. Unfortunately all of these subjective methods of gait analysis are insensitive and unreliable methods of assessment. Some specialist centers now have access to threedimensional motion capture and force platform systems allowing objective assessment of movement – in the future these facilities may become more readily available to practitioners.
Joint manipulation is harder to interpret in cats who often show less obvious evidence of pain or discomfort but may be generally more resentful of the examination process. Assessment of physiological parameters such as heart rate and respiratory rate is not a reliable indicator of pain in cats. Joint swelling, reduced range of movement and crepitus are infrequently reported in cases of feline OA. Joint thickening may be evident – although this tends to be less marked than in the dog – and the elbows are most commonly affected by this.
In contrast to dogs with OA, lameness and reduced range of movement on joint manipulation are not common features perhaps due to the cats’ lighter frame and ability to compensate for painful joints. Reduced jumping ability and reduced height of jump are common features – for example these were seen in around 70% of cats in one study (4). The lack of lameness as a common feature has meant that, especially in the past, any radiographic changes were ascribed as being not clinically significant by some clinicians.
Come back next week for Part 2 covering diagnosis and treatment!
1. Hardie EM, Roes SC, Martin FR. Radiographic evidence of degenerative joint disease in geriatric cats: 100 cases (1994-1997). J Am Vet Med Assoc 2002; 220: 628-632.
2. Clarke SP, Mellor D, Clements DN, et al. Prevalence of radiographic signs of degenerative joint disease in a hospital population of cats. Vet Rec 2005; 157: 793-799.
3. Godfrey DR. Osteoarthritis in cats: a retrospective radiological study. J Small Anim Pract 2005; 46: 425-429.
4. Clarke SP, Bennett D. Feline osteoarthritis: a prospective study of 28 cases. J Small Anim Pract 2006; 47: 439-435.
5. Lascelles BDX, Robertson SA, Gaynor JS. “Can Chronic Pain in Cats be Managed? YES!”, VIN’s Managing Pain Symposium 2003, www.vin.com.
6. Rosen S. Rehabilitation therapy for pets. Proceedings of the Hill’s European Symposium ‘Moving on with Mobility’ 2007, 44-48.
This article was previously published in 2012.