Feline Arthritis- Part 2
While clinical and historical findings may give many clues that the cat is suffering from OA, radiography is generally required to confirm this. For owners of elderly cats, this may present a stumbling block in diagnosis due to reluctance to sedate or anesthetize their cat. In these cases, clinical judgment should be used to decide whether or not radiography is essential.
Radiographs of painful joints can be taken under sedation (for example following administration of a combination of intramuscular 5-8 mg/kg ketamine and 0.25 mg/kg midazolam). If the gait abnormality is not localizable then two views of the elbows, stifles and a ventrodorsal pelvic radiograph are indicated as a starting point since these joints are most frequently affected. Intravenous fluid therapy is recommended whilst the cat is sedated or anesthetized, particularly if dealing with an elderly animal. Acepromazine, other hypotensive agents and non steroidal antiinflammatories should also be avoided in these animals due to concerns over renal side-effects.
Radiographic findings in animals with OA include:
•Peri- and intra-articular new bone (osteophytes, enthesiophytes)
•Narrowing of joint spaces
•Sclerosis of the subchondral bone
•Soft tissue thickening/swelling around the joint and/or involving the joint capsule
Any of these radiographic changes should be interpreted as being potentially clinically significant. It is important to remember that radiographs can be insensitive in illustrating OA since they are best able to show bony changes and do not identify lesions in the cartilage or synovium. Radiographic changes can be subtle even in animals with marked OA. Radiography should therefore be viewed as an aid to diagnosis of OA in cats.
Synovial fluid collection and cytological and bacteriological evaluation are rarely indicated in cats with OA. Indications for collection and analysis of joint fluid would include:
•If multiple joints are involved
•If the animal is young or middle-aged and an obvious traumatic or developmental cause is not apparent (e.g. hip dysplasia, cruciate ligament rupture)
•If an effusion(s) is(are) present
Immune-mediated polyarthritis is most frequently diagnosed in young-middle aged cats in contrast to OA which is more common in older cats.
Fasted blood and urinalysis is indicated to look for concurrent problems with an initial emphasis on basic hematology, serum biochemistry, total thyroxine and urinalysis to evaluate for common concurrent problems such as renal disease, hyperthyroidism and diabetes mellitus.
Treatment of feline OA is aimed at improving quality of life through symptomatic and supportive measures which ideally help increase mobility and activity, reduce pain, provide support for any disability, reduce the possibility of further joint damage and improve quality of life in general. Available treatment falls into the following categories – surgical treatment, environmental and management strategies, analgesic therapy, joint supplements, dietary therapy, physiotherapy and weight management.
Surgical therapy: In certain cases, surgical treatment will be an appropriate option to consider. Examples would include cats with cranial cruciate rupture (especially large cats), cats with joint instability (where arthrodesis may be indicated) and cats with severe hip dysplasia (where an excision arthroplasty may be indicated). Surgical intervention is generally indicated as a salvage procedure in these cases and is usually reserved for the later stages of disease when medical treatment and other options have failed to provide sufficient pain relief or adequate functionality.
Environmental and management strategies: Recommendations for these will vary depending on the nature and extent of problems reported by the owner. For example, strategies which should be considered include:
1. Cats with indoor toileting problems as a result of their OA: provision of low sided (easy access) litter boxes in all areas of the house that the cat uses (trying to avoid making the cat negotiate a flight of stairs to find a litter tray). Consideration towards the litter substrate – for example not too deep and difficult for the cat to navigate.
2. Provision of food, and especially water, on all levels of the house and where the cat spends its time to ensure that it does not have to travel too far.
3. Use of ramps and steps or ‘staging posts’ to allow access to raised areas (e.g. sofa, bed, chairs) which the cat may like to sleep on. Most cats feel safer on raised levels so this is especially important for those cats living in multi-cat, multi-animal or children-shared accommodation.
4. Use of padded bedding to protect the joints.
5. Heated beds, especially those that can be left on permanently, can be very popular with arthritic cats.
6. Cats finding it difficult to groom can benefit from being brushed by their owner.
Pain relief is an effective treatment for cats with OA. For many years, long term analgesia has been very difficult to achieve in cats – partly due to the lack of suitable therapeutic agents and partly due to differences in feline drug metabolism that mean that safe therapy with common canine analgesics such as the non steroidal anti-inflammatories (NSAIDs) has not always been possible in cats. Several NSAIDs are licensed for short term treatment of pain in cats. In recent months, a veterinary license has been granted to meloxicam for ‘alleviation of inflammation and pain in chronic musculo-skeletal disorders’ in cats in Europe (Metacam® 0.5 mg/ml, Boehringer Ingelheim). The licensed regime involves a starting dose of 0.1 mg/kg on day 1 and 0.05 mg/kg/day thereafter. There is no stated limit to duration of therapy. The lowest effective drug dose should be used in cats receiving this therapy. All NSAIDs carry a potential risk for gastrointestinal side-effects (anorexia, vomiting, diarrhea) and renal toxicity therefore owners should be advised of these and pre-treatment assessment of renal parameters is indicated.
As a minimum, fasted blood urea, creatinine, phosphate and electrolytes should be checked in addition to urine specific gravity. Azotemia in combination with a urine specific gravity of less than 1.035 is consistent with renal insufficiency and warrants a choice of alternative analgesic therapy or reduction in NSAID dosage and close monitoring. NSAIDs should not be used in dehydrated animals, animals with poor circulatory function (e.g. cardiac disease), those receiving glucocorticoids, ACE inhibitors, diuretics or other NSAIDs, animals with pre-existing thrombocytopenia, gastrointestinal or liver disease.
Alternative non-veterinary licensed preparations/ routes of analgesic treatment include opiates such as 20 μg/kg buprenorphine (which can be given 2-4 times a day by the sublingual route). Although buprenorphine is generally accepted as a very effective analgesic, some cats may show unwanted side-effects such as behavioral changes (euphoria), dilated pupils and inappetence. Some clinicians have used transdermal fentanyl patches in cats with OA (Figure 5) but these can be very expensive in the long term, this is an unlicensed therapy with human health and safety issues and the analgesia provided can be inconsistent.
Tramadol is a synthetic opiate μ-receptor agonist that also inhibits reuptake of serotonin and nor-adrenaline. Although there are only anecdotal reports of its use, these have been encouraging (5). A dose of 2-4 mg/kg twice daily has been proposed. Documented side-effects include vomiting and sedation although these are generally transient.
In cats with severe disease, a multimodal approach is justified – for example combining opioids with NSAIDs. Other agents which have been used, but where only anecdotal support exists, include tricyclic antidepressants (e.g. amitriptyline), NMDA antagonists (e.g. amantadine) and anticonvulsants (e.g. gabapentin). Clinicians using these unlicensed drugs and combinations should be aware of the limited safety data available and thus potential for side-effects.
Glucocorticoids are not recommended for the management of feline OA since although they are potent anti-inflammatories, they may also result in cartilage damage by reducing the synthesis of collagen and other matrix substances. Glucocorticoids also risk systemic side-effects and exacerbation of concurrent diseases such as renal disease and diabetes mellitus.
Chondroprotective joint supplements
For many years chondroitin and glucosamine supplements have been advocated for treatment of humans and dogs with OA so it is only natural that this has now extended to include cats. The rationale for use of these agents is that they contribute to a slowing of cartilage degradation and the provision of precursors required for cartilage repair. Chondroitin is a glycosaminoglycan found in articular cartilage, while glucosamine is a precursor for glycosaminoglycan production and is also used for production of hyaluronic acid by synovial cells.
None of the injectable preparations of chondroprotectants (e.g. polysulphated glycosaminoglycan, pentosan polysulphate, hyaluronic acid) are licensed for use in cats and there is no published data to support their use. A wide number of different oral supplements are available as nutraceuticals (i.e. not requiring a license to treat animals) and are proving popular with clinicians in spite of the lack of published, objective data to support their efficacy in the cat. Based on knowledge from other species, a supplement containing both chondroitin and glucosamine is indicated since these agents are thought to be synergistic in combination. Cats are often more difficult to dose with supplements and are more suspicious of agents mixed into their food which can make consistent dosing tricky.
In recent years, more attention has been placed on dietary therapy for canine OA cases and there are now feline diets which are indicated for treatment of cats with mobility disorders. These diets are modified to contain fatty acids such as alpha linoleic acid and docosahexenoic acid which have been shown to have anti-inflammatory and anti-cartilage degradation effects in vitro. These diets also contain antioxidants such as Vitamins C and E, agents that enhance cartilage synthesis such as methionine and glycosaminoglycans, natural glucosamine and chondroitin sulphate and L-carnitine and lysine to aid obesity management and encourage build-up of lean muscle. At this stage there is no published in vivo data to support the efficacy of these similar diets having helped to improve clinical signs of OA in affected dogs.
Physiotherapy techniques (e.g. massage, passive joint manipulation, stretching exercises) may be an option of some value in cats that are reluctant to exercise and where they will allow their owners to do this. Some cats will also accept and benefit from swimming therapy which has the benefit of providing muscle and joint activity without weight-bearing (6). Controlled exercise, recommended in dogs with OA, is generally hard to enforce in cats!
Acupuncture techniques can be helpful in decreasing the pain associated with muscle spasms by inducing release of neurotransmitters which reduce processing of pain signals and induce central release of endorphins.
Obesity management (Figure 6) should be introduced where required but is less frequently indicated in cats with OA than their canine counterparts.
It is recommended that animals receiving NSAIDs should have their serum biochemistry and packed cell volume re-checked one week after starting treatment and thereafter every 6 weeks (5). In addition, therapeutic efficacy and evidence of clinical and subclinical adverse effects should be established from the history and physical examination.
Other animals should be reassessed 2-4 weeks after any management or therapeutic changes have been made. The prognosis with treatment is highly variable depending on the severity of disease and any associated concurrent disease.
Click here to read Part 1 covering history and clinical examination!
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.