Osteoarthritis (OA), also known as degenerative joint disease, is a progressive and non-curable condition which causes degeneration of articular cartilage, fibrosis of peri-articular tissue and new bone formation. It is estimated that 20% of the canine population in the UK over 1 year of age have some form of OA (Johnston, 2001). There are two types of OA — primary and secondary. Primary OA implies that there are no inciting causes involved in the disease but, as this is unlikely, idiopathic OA is a more accurate term. OA is usually secondary to previous joint damage such as trauma or developmental disorders (George and Slater, 2003).
Clinical signs
Dogs with OA commonly present with abnormal gait, lameness, pain in affected joints, crepitus in extension or flexion of joints, exercise intolerance, muscle atrophy, and stiffness.
There are also behavioural signs that owners may put down to ‘old age’ rather than chronic pain associated with this disease. These may be restlessness, changes in sleep pattern, increased irritability or aggression, reduced social behaviour, depression, and anxiety (Grant, 2006).
Diagnosis
Diagnosis is based on history, physical examination and radiographs. Arthrocentesis can be performed to rule out any other causes of OA (Grant, 2006). Radiographs taken of the affected joints can show narrowing of the joint space, joint effusion, new bone formation at joint margins (osteophytes), and attrition and remodelling of subchondral bone known as subchondral bone sclerosis (Figure 1).
Treatment
There is no cure for OA but quality of life can be greatly improved by appropriate therapies. This is an important point to communicate to the owners and it is vital that they understand this from the very beginning. This is a key role for the veterinary nurse. Treatment aims to reduce inflammation, provide pain relief, maintain joint mobility, prevent further progression of the disease and improve quality of life (Marcellin-Little, 2009).
Weight management
Increased load on arthritic joints can participate in cartilage degeneration. It is worth noting that patients with OA may have difficulty controlling their weight as they may have some degree of exercise intolerance, or they may be on a restricted exercise regimen to prevent overexertion. Weight loss can significantly reduce lameness in dogs with OA as less stress is placed on the affected joints (Anthony 2005; Marshall et al, 2010). A study performed on 14 obese dogs that were placed on a restricted calorie diet for 16 weeks showed a significant reduction in lameness as their body weight reduced (Marshall et al, 2010).
Controlled exercise
Overuse of the affected joints may accelerate the destruction of the joint and worsen the clinical signs including pain. However, it is also important that some exercise is encouraged to maintain muscle tone and keep joints flexible. Howarth et al (2007) state that the clinical signs of degenerative arthritis improve with exercise.
An exercise plan consisting of short, frequent lead walks should be implemented. Care should be taken when telling owners to avoid excessive exercise in their dogs as it is difficult to assess what is too much; most dogs get so excited at the prospect of going for a walk that any signs of discomfort are hidden.
Hydrotherapy is an excellent form of exercise for dogs with OA, as the water produces a non weight-bearing environment, allowing dogs to use their limbs without added weight on the affected joints (Sharp, 2008).
Pain relief
OA is the most common cause of chronic pain in dogs. Chronic pain is described as pain lasting more than 3 to 6 months. It can be constant or intermittent and vary in its intensity. Chronic pain can exist beyond, and also in absence of, the original painful stimulus. This is called sensitization (Grant, 2006). This type of pain can reduce a dog's quality of life.
The subtle changes of chronic pain associated with OA often go unnoticed by owners or are put down to normal ageing. Grant (2006) suggests that owner compliance is a major issue when it comes to giving long-term medication for pain that they cannot understand; owners tend to be more aware of pain in their pets if there is a visible injury. Some signs of chronic pain that owners may observe are sleep disturbances, loss of appetite, aggression, depression, reduced activity and lowered pain threshold.
There are two main sources of pain in OA — synovial inflammation and sensitization of the pain pathway of the joint. When cartilage is broken down it releases breakdown products into the joint causing inflammation of the synovial membrane. The synovial cells then release pro-inflammatory mediators such as prostaglandins which stimulate further cartilage degradation. They also directly stimulate joint nociceptors to generate pain (Grant, 2006).
Continual cartilage damage and degradation means that inflammatory mediators are constantly being released into the joint. Silent nociceptors, which usually remain unresponsive, are activated to generate pain in response to innocuous stimuli such as stretching and weight bearing (Grant, 2006).
The aim of pain management in OA is to provide enough analgesia so that patients can use their affected limbs normally which, in turn, will minimize stiffness and muscle atrophy (Grant, 2006).
Non-steroidal anti-inflammatory drugs (NSAIDs)
NSAIDs such as carprofen, meloxicam, and firocoxib are the most common treatment for dogs with osteoarthritic pain (Innes et al, 2010). The aim is to establish a minimum effective dose. Grant (2006) states that after an initial period of 1 to 2 weeks the patient should be reassessed and the dose lowered if possible to a maintenance dose. Acute flare-ups occur occasionally, so doses may need to increase at these times. Eruptions of pain are most likely to be caused by overexertion or cold weather, but there is no evidence to support the latter (Marcellin-Little, 2009).
Studies on the long-term safety and efficacy of treatment with NSAIDs have shown that there is a clinical benefit of longer-term (28 days or more) usage with a low risk of side effects (Innes et al, 2010). Another study of a 52 week treatment course with firocoxib at 5 mg/kg once daily showed high proportions of dogs showing improvement of clinical signs with the greatest benefit seen within the first 3 months (Autefage et al, 2011). Out of the 39 dogs that took part only four dogs were withdrawn from the trial due to side effects which included increased levels of creatinine (two dogs), diarrhoea (one dog), and a fatal duodenal perforation due to accidental double dosage (one dog).
Owners should be made fully aware of the potential side effects associated with NSAIDs and cease administration if any occur. These include renal and hepatic dysfunction, gastric irritation and ulceration. Owners should monitor their dogs for vomiting, diarrhoea, inappetance, polyuria, and polydipsia. It is suggested that bloods should be run pre-treatment and at regular intervals during treatment (Grant, 2006; Marcellin-Little, 2009). As OA usually manifests itself later on in life it may be possible that dogs are already showing signs of renal or hepatic disease therefore other analgesics, such as tramadol or gabapentin, may have to be considered (Marcellin-Little, 2009).
Environmental enrichment
Physical measures can also be undertaken to increase the comfort of arthritic dogs, such as providing soft thick bedding, non-slip flooring, and easy access to water and food (Figure 2). In humans, psychological therapies are used in the treatment of chronic pain to minimize stress, anxiety and negative thoughts, often via counselling. Obviously in dogs this cannot be done, but diversion therapy can be used to decrease their perception of pain. Distraction in the form of toys, grooming, different walking routes, and sniff and search food games work well (Grant, 2006).
Clinical diet
Lumbus and Chan (2008) suggest diet can be used to modulate the progression of the disease. However, there is currently not enough evidence to suggest strong positive effects of these diets so they should be used alongside proven methods of pain relief such as NSAIDs.
There are several different commercial diets available for dogs with OA in which omega-3 fatty acids are often included. These replace some of the arachidonic acid (an omega-6 fatty acid) in cell membranes, thus fewer damaging inflammatory mediators are produced. Therefore, this could potentially decrease joint inflammation (Anthony, 2005; Lumbus and Chan, 2008; Marcellin-Little, 2009).
Other important components of specialized diets are nutraceuticals, which are nutrients thought to elicit pharmacological effects. These include green lipped mussel, glucosamine, and chondroitin sulphate. Glucosamine is a glycosaminoglycan (GAG), which is a component of extracellular matrix of joint cartilage. Normal chondrocytes are able to synthesize their own glucosamine, but those in osteoarthritic dogs lose this ability (Anderson, 1999). Adding glucosamine to the diet is thought to enhance therapeutic management of dogs with OA. It is suggested by Grant (2006) that glucosamine may be contraindicated in diabetic patients, or those at risk of developing diabetes, as it may raise blood glucose levels.
A systemic review of recent studies on the management of OA showed that there was moderate evidence for the effectiveness of nutraceuticals, but further high quality studies are needed (Sanderson et al, 2009).
Hyaluronan is another glycosaminoglycan which can be injected intra-articularly. It was previously thought that this may actually exacerbate the clinical signs of OA (Smith et al, 1998), but a more recent study by Brandt et al (2004) showed that this is not the case. However, Sanderson et al, 2009 report that there is no evidence that hyaluronan is a successful treatment in OA and more studies are needed.
Arthritis clinics
Arthritis clinics run by veterinary nurses are a good way of educating owners on OA and the treatments available. Veterinary nurses can work with the owners to devise a management plan (consisting of controlled exercise, monitoring pain, dietary supplementation, and weight loss if necessary) that fits around their lifestyle and commitments. This way owner compliance is more likely to be achieved, which is very important when managing a disease that a lot of owners think is normal for an ageing dog.
It is vital that owners understand what changes need to be made to their dog's lifestyle as successful OA management relies heavily on owner compliance. Further check ups at these clinics enable VNs to monitor the patient's progress and adapt the plan as necessary. Studies reveal that owners are a valuable source of information with regards to noting behaviour changes associated with chronic pain (Wiseman et al, 2001).
Hydrotherapy
Hydrotherapy is an ideal form of controlled exercise for a dog with OA. A study of 89 hydrotherapy centres in the UK reported that 18% of the cases were being treated for OA (Waining et al, 2011). During hydrotherapy patients with joint pain can move their limbs more freely through the usual range of movements (ROM) without added weight on the joint, which is pain relief in itself (Grant, 2006).
Hydrotherapy provides pain relief and muscle relaxation, encourages joint mobility, improves muscle tone, and reduces swelling and stiffness. Sharp (2008) suggests the temperature of a hydrotherapy pool should be between 26 and 30°C. The warmth of the water helps to dilate blood vessels, allowing more oxygenated blood to flow around the body. This increases cell metabolism so helps to eliminate toxins that build up in disused limbs (Figure 3).
The hydrostatic pressure of water helps reduce swelling. The deeper the water is the greater the hydrostatic pressure. Water is more viscous than air so there is more resistance when moving through it. Working against this resistance helps to build up muscle strength (Sharp, 2008).
Some hydrotherapy units may have an underwater treadmill (Figure 4). The added benefits of working a dog on a treadmill are the sensory input of the feet touching the floor of the treadmill, and the alteration of the depth of the water. Table 1 shows that as water level rises it takes more of the dog's weight. (Levine et al, 2002).
| Water level | Percentage of body weight carried by dog (%) |
|---|---|
| Dry land | 100 |
| Up to hock | 91 |
| Up to stifle | 85 |
| Up to hip | 38 |
There are some contraindications to using hydrotherapy to treat OA. These are fear of water, open wounds, faecal incontinence, vomiting, coughing, infections that could be passed on to other dogs, and cardiovascular disease (Sharp, 2008).
Physiotherapy
Physiotherapy aims to reduce pain, increase and maintain both joint flexibility and muscle strength, and promote healing. VNs can carry out physiotherapy under the direction of a veterinary surgeon (Sharp, 2008); those that carry out physiotherapy should be confident and competent with the basic techniques such as massage, effleurage, and passive joint movements. It should be performed on a regular basis to be effective and, if done correctly, it can reduce pain and stimulate the release of endorphins to promote muscle relaxation (Grant, 2006). A 21 day study by Crook et al (2007) showed that passive stretching with a hold of 10 seconds twice daily significantly increased the ROM of arthritic joints by 7–23%.
Massage
This is best used at the beginning of a physiotherapy session as it reduces tension and anxiety. It increases lymphatic and venous drainage which can relieve pain by removing noxious chemicals by circulation. It also releases endorphins, and reduces muscle fatigue (Sharp, 2008).
Effeurage
Effleurage is the firm stroking in the direction of venous blood flow. In the limbs this means starting at the paw and stroking proximally towards the nearest group of lymph nodes — in the axilla or groin. This increases venous return therefore reducing any swelling (Sharp, 2008).
ROM
ROM can be performed once the limbs have been warmed up (Figures 5 and 6). It is important for joints to be moved gently through their usual ROM regularly to maintain the joint's flexibility. These passive movements are used to increase circulation, prevent adhesions in articular capsules, increase synovial fluid production and diffusion, prevent muscle and ligament contracture, maintain joint mobility, reduce pain, promote muscle relaxation, and stimulate mechanoreceptors (Sharp, 2008). A study has shown that massage and ROM (collectively referred to as physiotherapy) combined with weight reduction is effective in dogs with OA (Mlacnik et al, 2006).
Alternative therapies
Although outside the scope of this review, there are other therapies that claim to help relieve joint pain. These include acupuncture, thermotherapy, cryotherapy, transcutaneous electrical nerve stimulation, laser and ultrasound therapy (Grant, 2006).
Conclusion
OA is a very common disease in older dogs. Clinical signs are such that, if left untreated, they can impair the dog's quality of life. Treatment relies very much on owner compliance so it is extremely important that owners are educated on the debilitating effects of OA. This is where arthritis clinics run by veterinary nurses can be helpful in providing information and monitoring a patient's response to treatment. To date there are not enough studies to prove the effcacy of many of the available treatments for these dogs so more research needs to be done.