Osteoarthritis is the most common chronic pain condition in dogs and cats, difficult to recognise early, challenging to treat and unavoidably has a progressive pathology. In cats, osteoarthritis is also referred to as degenerative joint disease (DJD).
Source of Pain
Osteoarthritis is a disease of bone and cartilage, and physical examination frequently elicits crepitation in the joints. Nevertheless, the pain of osteoarthritis is not felt at the articular surfaces; rather, pain is largely felt in the peri-articular structures, such as pain due to inflamed synovium; tension placed on a fibrotic joint capsule; and patients exerting pressure on weakened ligaments, tendons, and muscle. Therefore, osteoarthritis is a disease of the entire joint, including synovitis, fibrosis, and atrophy, and it results in pain and progressive disability. Most of the canine osteoarthritis is not simply wear-and-tear in origin but conformational, and cats have a very high incidence of osteoarthritis across all ages.
While the pathophysiology of osteoarthritis may perhaps be different in dogs and cats, osteoarthritis in both species begins early in life—far earlier than in humans. Medicinal efforts to address osteoarthritis in veterinary patients are quite different from one life stage to another.
List 1: Canine conformational origins of osteoarthritis
Canine conformational origins of osteoarthritis
Chondrodysplasia
Elbow dysplasia (coronoid, anconeal)
Heritable predisposition cruciate ligament disease (rupture)
Hip dysplasia
Luxating patella
Osteochondritis dissecans
Management of osteoarthritis
The two most important methods at the top of the evidence-based pyramid for management of osteoarthritis are:
Weight optimisation
Non-steroidal anti-inflammatory drug (NSAID) therapy.
In dogs and cats, weight optimisation and NSAID therapy are the two highest levels of therapeutic measures along with other modalities extra to these that include supplementary pharmacologic and nonpharmacologic modalities to manage the chronic maladaptive pain of canine and feline osteoarthritis. Besides, multimodal drug therapy, particularly, NSAID-opioids combination is more effective for pain management than single drug administration.
1. Weight optimisation
Central obesity (abdominal fat) doubles the risk for chronic pain from any cause. In overweight dogs with existing hip dysplasia or osteoarthritis, clinical improvement is always recorded in patients that undergo weight loss, with as little as only a 6% reduction in body weight.
In cats, obesity leads to a higher risk of lameness presentation to a veterinarian though with weak radiographic osteoarthritic changes.
Weight optimisation has a dual purpose, both preventatively and therapeutically. An overweight patient dramatically, and negatively, affects its propensity for osteoarthritis and severity of the disease. In an obese patient, weight loss should be a primary treatment rather than a secondary afterthought.
2. Non-steroidal anti-inflammatory drug (NSAID) Therapy
Regrettably, lots of dogs and cats with existing osteoarthritis cannot exercise to lose weight due to the underlying pain and inflammation caused by the disease. Osteoarthritis is an inflammatory disease that leads to central and peripheral sensitisation. Therefore, NSAIDs are a key pharmacologic intervention for osteoarthritis in both dogs and cats (List 2).
List 2: Chronic Pain Management: Veterinary NSAIDs
Drug Dosage Dogs Carprofen (Rimadyl) 2.2mg/kg orally every 12hrs Deracoxib (Deramaxx) 1-2mg/kg orally every 24hrs Firocoxib (Previcox) 5mg/kg orally every 24hrs Meloxicam (OroCAM) 0.1mg/kg orally every 24hrs
Cats Meloxicam (OroCAM) 0.3 mg/kg orally on day 1, then 0.1 mg/kg daily Ketoprofen (Ketofen) 1‐0 mg/kg orally once daily
NSAIDs Long-Term Use & Safety
Consistent use of veterinary-approved NSAIDs at the recommended doses for canine osteoarthritis leads to continued improvement for over 6 months to 1 year. In cats, the safety of long-term oral meloxicam is achieved at below-label doses while for robenacoxib safety in cats can be achieved even at 5 times the labelled dose for 6 months.
The most common adverse events are gastrointestinal (GI) in nature; clinical signs noted are (in order of most common):
Vomiting
Diarrhoea
Inappetence for both dogs and cats.
Gastric erosion and ulcers
Adverse effects for NSAIDs
Adverse effects most often occur within 2 to 4 weeks of initiating treatment, and clinical signs usually resolve when the drug is withdrawn, and gastroprotection therapy is initiated. Gastric erosion and ulcers can occur during NSAID therapy, and it is possible but unlikely, for these conditions to manifest without clinical signs and lead to perforation. The most common reason for perforation is the concurrent use of another NSAID or corticosteroid, administration of high dosages, or a combination of these.
The second most common adverse effect is nephrotoxicity (kidney failure); patients at highest risk are those with low-flow states (ie, hypotension, hypovolemia, congestive heart failure, sodium depletion, furosemide administration) and/or pre-existing chronic renal disease.
Once weight optimisation and NSAID therapy have been implemented—other modalities rise to the top.
Polysulfated Glycosaminoglycans
Polysulfated glycosaminoglycan (PSGAG) is a semi-synthetic glycosaminoglycan prepared from bovine tracheal cartilage. It is composed of a polymeric chain of repeating disaccharide units. The primary glycosaminoglycan in PSGAG is chondroitin sulfate. These are called Nutraceuticals, products which other than nutrition are also used as a medicine, providing a physiological benefit and protection against chronic disease. Starting the use of oral nutraceuticals early in life, particularly for at-risk breeds, is safe and may provide some long-term chondroprotective (joint protection) effect. Examples are as shown below.
List 3: On- and Off-Label Use of Polysulfated Glycosaminoglycans
On-Label Dose: Dogs Off-Label Use Comments
Adequan 4.4mg/kg IM Dogs and cats Caution with
twice weekly Administer SC patients at risk
for 4 weeks Continue on long-term for bleeding
basis, (e.g., monthly and dyscrasia
adjusting frequency
according to patient needs)
Cartrophen Vet 3 mg/kg SC Continue on a long-term
every 5—7 days, basis, (e.g., repeat protocol
4 times every 4—6 months)
Omega-3 Fatty Acids
Pets with a healthy weight can be given omega-3 fatty acids supplementation to fight inflammation which is a natural response to infections and damage to the body. Higher omega-3 intake reduces inflammation and improves bone strength and joint health, possibly reducing the risk of osteoporosis and arthritis by decreasing inflammation and pain associated with arthritis.
What foods provide omega-3s?
Omega-3s are found naturally in some foods and are added to some fortified foods. A variety of foods containing omega-3 fatty acids include the following:
Fish and other seafood (especially cold-water fatty fish, such as salmon, mackerel, tuna, herring, and sardines)
Nuts and seeds (such as flaxseed, chia seeds, and walnuts)
Plant oils (such as flaxseed oil, soybean oil, and canola oil)
Fortified foods (such as certain brands of eggs, yoghurt, juices, milk, soy beverages, and infant formulas)
What kinds of omega-3 dietary supplements are available?
Omega-3 dietary supplements include:-
Fish oil,
Krill oil,
Cod liver oil,
Algal oil (a vegetarian source that comes from algae).
Omega 3s include EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid), and Alpha Lipoic Acid (ALA). For dogs with osteoarthritis, Eicosapentaenoic acid (EPA) is recommended while for cats with osteoarthritis, Docosahexaenoic acid (DHA) is recommended.
Therapeutic Exercise
Controlled, prescribed exercise can be beneficial to dogs and cats due to a variety of mechanisms, including:
The Gate Theory of pain (The spinal cord has a functional, neurophysiologic “gate” that can either block or allow pain signalling to the brain during exercise (e.g., proprioception).
Activation of endogenous opioids
Enhanced strength of periarticular soft tissue (e.g., muscle, tendon, ligament) and resulting in improved micro-stability of joints
Weight loss (if needed).
Non-pharmacologic Management of Pain
Most nonpharmacologic techniques include:-
1. Electrostimulation (modalities include transcutaneous electrical nerve stimulation (TENS), interferential therapy, and electroacupuncture),
2. Local tissue cooling (cryotherapy),
3. Therapeutic heat produced by either deep (therapeutic ultrasound) or superficial (moist hot packs, immersion baths, infrared light), and
4. Manual therapy (manual modalities include joint manipulation/mobilisation and massage).
These techniques are time- and thus cost-intensive and may require specialised training.
Other Measures to Improve Comfort in arthritic animals
Environmental and physical factors can exacerbate the pain that results from disease or injury. Non-pain sources of discomfort or distress, such as nausea, hunger, dehydration, dizziness, or weakness, should always be considered. Changes in environment, such as deeper or softer bedding, alternative feeding strategies, dim lights, or warmer temperatures may improve the comfort of debilitated animals or those with lower pain thresholds. The use of other appropriate supportive measures, such as parenteral fluid supplementation and wound care, are critical adjuncts to optimise animal comfort and welfare.
Further Reading
References
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K. A. Mathews, "Neuropathic pain in dogs and cats: if only they could tell us if they hurt," Veterinary Clinics of North America: Small Animal Practice, vol. 38, no. 6, pp. 1365-1414, 2008.
R. A. Gupta and R. N. DuBois, "Colorectal cancer prevention and treatment by inhibition of cyclooxygenase-2," Nature Reviews Cancer, vol. 1, pp. 11-21, 2001.
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