Osteoarthritis is a degenerative and low-grade inflammatory disease that affects humans, companion, and captive animals (Cimino Brown, 2017; Mobasheri et al, 2021). Cartilage, synovium, subchondral bone, and the crosstalk between these tissues are central components of osteoarthritis development (Berenbaum et al, 2013; Findlay and Kuliwaba, 2016). Chronic pain that involves both nociceptive and neuropathic mechanisms (Lowe, 2021) develop into negative consequences related to pain, mobility, and decreased quality of life (Figure 1).
Clinical issues that are seen with ageing, geriatric patients are decreased proprioception and muscle atrophy (Goldberg et al, 2021). Medical issues that occur frequently are obesity, neoplasia, degenerative joint disease (DJD), and loss of sensory acuity (Goldberg et al, 2021). Both these clinical and medical issues will compound the advancement and severity of osteoarthritis (Box 1).
Box 1.Patients at risk for osteoarthritis
- All large breed dogs over 6 years
- All giant breed dogs over 4 years
- All dogs with congenital issues — hip dysplasia, elbow dysplasia, etc.
- All dogs with history of past orthopaedic injury, especially those involving a joint
- All athletes
Osteoarthritis negatively affects the quality of life in geriatric dogs and is a common concern of dog owners. Both the incidence and severity of osteoarthritis increase with age in dogs (Bellows et al, 2015). Osteoarthritis affects larger breeds of dogs more frequently than smaller breeds, but the incidence and severity vary among joints, and clinical signs can range from nonexistent to incapacitating (Hedhammar et al, 1979; Johnston, 1997; Rychel, 2010). Osteoarthritis can affect any joint, including hips, elbows, and stifles, but also vertebral facet joints, carpal joints, tarsal joints, and even metacarpophalangeal and metatarsophalangeal joints. (Franklin et al, 2009) (Figure 2).
Instability, incongruity, uneven load bearing, and injury to a joint predispose to osteoarthritis by setting a patient up for a lifetime of abnormal stress on intraarticular cartilage and chronic inflammation (Rychel, 2010). Examples of predisposing causes include elbow and hip dysplasia, orthopaedic surgery, rupture of the cranial cruciate ligament in the stifle, articular fractures, and incongruity resulting from trauma or angular limb deformity.
Part 1 of this two part article will look at the causes of osteoarthritis and its detection by owners and veterinary professionals, and will discuss the importance and methods of pain management. Part 2 will look at the physical rehabilitation modalities.
Behaviour
Behaviours that the owner may see early during the disease are the dog sporadically reluctant to perform previous tasks or activities, such as jumping into the car, which never posed a problem before. In the next stage, a lameness or stiffness occurs following periods of excess activity or over-exertion. These signs often disappear after several days of rest. As the degeneration progresses, the stiffness and lameness may be most pronounced following periods of rest. The pet typically ‘warms out’ of the signs with activity (Goldberg, 2017). Any cold or damp weather will increase the severity and duration of the symptoms. Continuous stiffness, lameness and chronic pain typify the final stage producing an irritable, reclusive, and restless pet (Box 2).
Box 2.Signs of canine osteoarthritis
- Stiffness after exercise
- Wasting away of muscle — atrophy
- Limited movement
- Pain
- Joint swelling
- Trouble getting up, laying down, walking, climbing stairs or jumping
- A grating sound in a joint
- Altered behaviour seen by owner
Clinical assessment
A comprehensive evaluation for osteoarthritis should include laboratory analysis, which will include specific testing for liver enzymes and kidney function; these tests are important in determining which pharmaceutical medications should be prescribed. The aim of imaging an affected joint is to document the signs of degenerative change in the joint and to demonstrate the cause of the abnormal joint mechanics that may have initiated the degenerative changes (Carrig, 1997). Common radiographic findings include subchondral sclerosis of bone, osteophytes, enthesophytes, and joint effusion (Millis, 2021). A nutritional assessment should include a body condition score, a muscle condition score, what the dog is fed with precise amounts, and what nutritional supplements are being used.
Incorporation of a pain assessment into the examination is essential for proper diagnosis and early intervention in the development of pain and arthritis. It is important to know the underlying cause of pain in an ageing animal and essential to rule out other disease processes, such as osteosarcoma, fungal disease, osteomyelitis, septic synovitis, and soft tissue injury (Rychel, 2010). A thorough orthopaedic examination begins with the dog in a standing position to palpate both forelimbs and then both pelvic limbs simultaneously for muscle atrophy and joint effusion (Millis, 2021). In-depth evaluation of joints may be performed with the dog standing or, preferably, in lateral recumbency. Beginning distally with the toes and proceeding proximally, each joint should be systematically evaluated for periarticular swelling, joint effusion, joint instability, crepitus, range of motion, and pain with manipulation. Muscle mass usually precludes assessment of the hip and shoulder joints for swelling or effusion. Any loss of range of motion or pain at the end of range generally indicates a problem with the joint. A neurological examination should be performed because brain size reduces with age as a result of atrophy of the cerebral cortex (Goldberg and Tomlinson, 2017). This is the part of the brain that controls the body's voluntary actions, so patients may be slower to react and slower to learn. There is a loss of fine motor control and decreased body awareness (proprioception). This may result in difficulty with balance and coordination, along with changes in gait (Goldberg and Tomlinson, 2017).
Client participation questionnaires
Currently, validated osteoarthritis/DJD questionnaire-based measurements of health, also called clinical metrology instruments (CMIs), have become the best way to begin evaluation of patients for chronic pain and mobility function. One of these questionnaires can be provided to the owner to fill out prior to the appointment. The veterinary staff (veterinarian and nurse) can fill out their version as the examination progresses. Those designed to assess chronic pain, use a combination of measures that assess stiffness, pain, gait, function, quality of life and pain severity. For dogs, these include:
- Helsinki Chronic Pain Index (HCPI) — (HielmBjörkman et al, 2009) 10 questions for owner
- Canine Brief Pain Index (CBPI) — (Brown et al, 2009; Essner et al, 2017) 11-point scale
- Cincinnati Orthopedic Disability Index (CODI) (Gingerich and Strobel, 2003) three domains and essay
- Health Related Quality of Life (HRQL) (Wiseman-Orr et al, 2006) 12 questions
- Liverpool Osteoarthritis in Dogs (LOAD) (Walton et al, 2013) three domains; 23 questions
- Canine Osteoarthritis Staging Tool (COAST) (Cachon et al, 2018) grades the dog and the joint using various questions.
Multimodal therapy
There is currently no cure or treatment for osteoarthritis, making effective management extremely challenging. Multimodal therapy is considered best practice. This multimodal therapy is beneficial because it allows for lower dosages of pharmaceuticals to be used, while also incorporating non-pharmacological therapy. Two important documents that offer guidelines for this management are:
- 2015 American Animal Hospital Association/American Association of Feline Practitioners (AAHA/AAFP) Pain Management Guideline (Epstein et al, 2015)
- World Small Animal Veterinary Association (WSAVA) Guidelines for the Recognition, Assessment and Treatment of Pain (Mathews et al, 2014).
Weight optimisation
According to the AAHA/AAFP (Epstein et al, 2015) and WSAVA Guidelines (Mathews et al, 2014), weight optimisation is the first principle in the management of osteoarthritis. A study from 2006 followed litters (48 Labrador Retrievers from seven litters). The conclusion of the study was that restricted feeding delayed or prevented development of radiographic signs of hip joint osteoarthritis in this cohort study of Labrador Retrievers. Lifetime maintenance of 25% diet restriction delayed onset and reduced severity of hip joint osteoarthritis, thus favourably affecting both duration and quality of life (Smith et al, 2006). Limit fed dogs developed radiographic osteoarthritis at 12 years (versus 6 years in the control group). Limit fed dogs also lived 2–2.5 years longer. Therefore, weight management is the first principle to slow the development of osteoarthritis.
Pet obesity has reached epidemic proportions in the United States and other industrialised countries. It is estimated that 35–40% of cats and dogs are overweight or obese (Lund et al, 2005, 2006). Most recently, in 2018, an estimated 60% of cats and 56% of dogs in the United States were overweight or obese (www.PetObesityPrevention.org). Several studies have shown that saturated fats trigger adipose (fat tissue) inflammation, which is not only an indicator for heart disease, but also worsens arthritis inflammation (Urban and Little, 2018).
The second principle, according to the AAHA/AAFP (Epstein et al, 2015) and WSAVA Guidelines (Mathews et al 2014) includes multimodal medications. The range of medications and modalities that can be used to manage pain is vast, each with slightly different benefits and precautions, so it is important to be well versed in the options available. While classes of drugs will be named in this review, in-depth details about dosages will not be discussed. It is recommended to read the AAHA/AAFP (Epstein et al, 2015) and WSAVA Guidelines (Mathews et al, 2014) for this information.
Pharmaceutical medications
Non-steroidal anti-inflammatory drugs (NSAIDs) are often the first drugs used for treatment of osteoarthritis in veterinary medicine. Blood work and urinalysis should always be performed before beginning an NSAID to rule out renal insufficiency and dehydration, both contraindications for administration (Rychel, 2010). Coadministration with a steroid medication is another contraindication. Written and verbal instructions need to be provided to the client, along with a client information sheet about the specific NSAID. Make sure the client understands that adverse drug events (ADEs) need to be reported immediately to the managing veterinarian. The number one ADE for NSAIDs is vomiting, and most often an ADE happens with the first 2–4 weeks of therapy initiation (Epstein and Goldberg, 2021). On each drug label should be written: ‘Warning: Discontinue and contact immediately if any vomiting, diarrhoea or diminished appetite occur’ (Epstein and Goldberg, 2021).
Grapiprant is considered a non-cyclooxygenase 2 (COX-2) inhibiting medication. It is a prostaglandin-receptor antagonist that targets the EP4 receptor that is involved in osteoarthritis-associated pain and inflammation (Dycus, 2018). It can be recommended for three groups of dogs:
- Younger dogs with a developmental disorder that need lifelong management of osteoarthritis
- Dogs with osteoarthritis secondary to injury
- Older dogs with ongoing osteoarthritis.
Gabapentin is an anticonvulsant. It enhances serotonin and norepinephrine. It is an N-methyl-D-aspartic acid (NMDA) receptor antagonist. It down regulates calcium channels and is a sodium channel blocker (Norkus, 2015). It has been adopted for treatment of pain related to osteoarthritis and cancer, and in neuropathic pain conditions, such as cervical disc disease. Applications for controlling neuropathic sensations such as burning, itching, pins and needles, and tingling have also been described (Albino, 2015).
Amantadine, another NMDA receptor antagonist, helps to turn off amplified pain signals sent to the brain for pain perception. It can be used for decreasing spinal cord windup in states of chronic pain, which most osteoarthritis patients experience because of long-term, unmanaged pain (Rychel, 2010). It is usually well tolerated even in geriatric, compromised veterinary patients (Lascelles, 2008).
Tramadol is a synthetic opiate drug that also acts on serotonin and adrenergic receptors to reduce pain in dogs and cats, and is commonly used in veterinary medicine. People continue to use it for osteoarthritis breakthrough pain even though there is no proof that the drug works in dogs because they do not produce the metabolite necessary to utilise tramadol (Budsberg, 2018).
Non-pharmaceutical agents
There are many avenues beyond pharmaceuticals that can be taken to make these patients comfortable. Other diseasemodifying osteoarthritis agents, such as joint supplements with glucosamine, chondroitin, omega-3 fatty acids, and polysulfated glycosaminoglycans, can be incorporated.
Acupuncture offers a compelling and safe method for pain management in veterinary patients, and should be strongly considered as a part of multimodal pain management plans. It is a minimally invasive treatment that, for most animals, is not uncomfortable, often pleasant, and can be used either alone or in addition to other pain treatment modalities (Epstein et al, 2015) (Figure 3).
Emerging modalities for osteoarthritis
Many of these newer therapies are not available in all countries. These are mentioned so that the reader can see what is under development for the future of osteoarthritis treatment.
Synovetin OA™ (Exubrion Therapeutics) is an intraarticular injection of a radionuclide of tin with medical applications for localised treatment of inflammation — it reduces synovitis and associated pain of canine joints afflicted with osteoarthritis (Donecker and Stevenson, 2017). It is considered a disease modifying device (Donecker and Fox, 2019; Fox and Donecker, 2019) because it reverses the inflammatory part of the synovitis. There must be special permits for facilities plus people trained in handling radioactive materials. The idea is to do a single targeted injection into a joint to provide long-term relief. More information can be obtained from: https://www.synovetin.com/resources/data-supporting-tin-117m
Resiniferatoxin (RTX) affects the transient receptor potential vanilloid receptor 1 (TRPV1 receptor). RTX is the purified form of capsaicin, which is found in hot peppers. This is an experimental drug and is not available on the market (Cimino-Brown, 2016).
There are two nerve growth factor monoclonal antibodies (anti-NGF mAb) of relevance to veterinary medicine for use in osteoarthritis patients. There is a canine-specific and a feline-specific one that have been developed. Because they are species specific, they are very well tolerated, have few side effects, and no major immunostimulation issues reported to date. The canine version, which goes by the chemical name of bedinvetmab and the trade name LibrelaTM (Zoetis) has been approved for use in Canada, the EU and Switzerland. The feline version, frunevetmab, which goes by the trade name SolensiaTM (Zoetis) has been approved for use in the EU and Switzerland. Canada is approving its use and the Federal Drug Administration has not approved it in the United States (Enomoto et al, 2019). The current data and ease of administration suggest that anti-NGF mAb therapy is poised to become a valuable and muchneeded advance in the management of canine and feline osteoarthritis (Epstein, 2019).
Quality of life
Quality of life (QOL) in animals has been defined as the affective (emotional) response of an individual animal to his or her circumstances, and the extent to which the circumstances meet his or her expectations. In the context of animal hospice and palliative care, QOL assessments reflect how an animal's physical, emotional, and social wellbeing is affected by disease, disability, or changes related to advanced age (Pierce and Shanan, 2017). There are specific tools that can be used in assessing QOL. The HHHHHMM scale, developed by Villalobos, is such a tool (Villalobos, 2009).
Conclusion
Rehabilitation objectives for the osteoarthritic geriatric patient include identifying the disease and managing the associated pain.
While osteoarthritis progression cannot be stopped, its progression can be delayed by weight management, pharmaceutical, non-pharmaceutical therapeutics, and physical rehabilitation, which will be discussed in part 2 on this article. Educating colleagues and clients to all that is currently available will encourage the best QOL for canine patients.
KEY POINTS
- Osteoarthritis is an incurable, chronic disease that can affect any breed of dog.
- Osteoarthritis is normally diagnosed through behaviour and clinical assessment.
- Clinical metrology instruments are extremely useful in the evaluation of osteoarthritis patients.
- Weight optimisation, pharmaceuticals and non-pharmaceutical therapy are the ways to manage osteoarthritis.
- Emerging modalities include new pharmaceutical medication techniques plus those that are under clinical investigation.
- Quality of life scales can be used to assess progress throughout the dog's lifetime with this incurable disease.