Canine joint disorders – effective OA treatments

Canine OA is one of the most common diseases encountered in general practice, affecting approximately 20% of adult dogs (Johnston, 1997). This has significant implications for quality of life and improving management of these patients will inherently improve the welfare of affected animals.

OA, also known as degenerative joint disease, is a result of deterioration of the articular cartilage and the process of changes to the joint, eventually resulting in pain and disability. In dogs, OA is usually secondary to joint instability, deformity, developmental disease (such as elbow dysplasia) or failure of endochondral ossification.

OA is a progressive disease process and no way has been found to halt it, despite huge amounts of research in both the human and veterinary fields. However, effective ways are available to slow the progression and limit the clinical signs associated with OA. This is done through a multimodal approach and requires an in-depth discussion with owners of arthritic dogs to ensure they understand the goals you are aiming to achieve have realistic expectations and improve compliance.

The key aspects to effectively managing OA are:

• weight management
• exercise modification and physiotherapy
• NSAIDs
• nutritional management
• additional analgesics
• surgery

Weight management

A large proportion (59%) of dogs in the UK are overweight (Courcier et al, 2010) and being overweight has multiple detrimental effects on any dog with OA.

The most obvious effect is a simple mechanical one: a dog that weighs 40kg when its ideal lean weight is 30kg (a typical Labrador retriever) will place 33% more force through each limb as it ambulates. We should be aiming to have any dog with OA at its lowest ideal lean bodyweight to limit the forces acting on each joint.

The effect of obesity and associated proinflammatory mediators (adipokines) has become recognised in human and veterinary medicine. It is likely that reducing the amount of adipose tissue a patient has will reduce the levels of these proinflammatory mediators, and may be beneficial in slowing the progression of OA and its associated clinical signs (German et al, 2010).

Weight reduction has been shown to result in a reduction in lameness in dogs with hip OA (Impellizeri et al, 2000). Frustratingly, while very effective, weight loss can be one of the most difficult aspects of OA management to achieve, as it requires significant discipline and commitment from owners. Frank discussion with clients, use of regular nurse weight clinics and formulating a diet plan for weight loss can be invaluable in achieving this goal.

Exercise modification and physiotherapy

Little evidence supports a specific exercise regime for dogs with OA; however, it has been shown that musculoskeletal strengthening in humans with chronic back pain can significantly reduce pain (Dreisinger, 2014) and it is reasonable these benefits would be applicable to our canine patients.

Unfortunately, scientifically proving this in canine patients is difficult as it relies on compliance from owners with regards to following an exercise plan, and the wide variation in size and stature of our patients makes designing a “one-size-fits-all” exercise regime impossible. Physiotherapy and hydrotherapy are becoming more widely accessible and involvement of a certified canine rehabilitation practitioner or veterinary physiotherapist can be helpful. Evidence exists to show hydrotherapy can increase range of motion of arthritic elbows in dogs (Figure 1; Preston and Wills, 2018).

NSAIDs

NSAIDs have long been the primary drugs of choice used to treat canine OA: they are effective analgesics, and reduce the degree of inflammation within the diseased joint. With any medication that has been on the market for a long time, it is easy to become blasé about its efficacy and seek alternative treatments in the hope they are superior.

Despite this, a systematic review has shown NSAIDs are the only drugs with strong evidence supporting their efficacy in the treatment of canine OA (Sanderson et al, 2009). NSAIDs will likely remain the cornerstone of any multimodal treatment plan for dogs with OA. Many NSAIDs are licensed for use in canine OA; however, the licensed durations of treatment vary between drugs within this group and careful reading of datasheets is recommended before longer courses are prescribed.

The side effects of NSAIDs are well recognised and it is prudent to check baseline renal parameters prior to commencing treatment, as well as regular monitoring if treatment is prolonged.

A new class of NSAID – piprants – has been licensed for use in Europe. Grapiprant is an EP4 prostaglandin receptor antagonist that acts further down the arachidonic acid pathway than traditional NSAIDs and aims to block EP4, a major receptor of prostaglandin E2, thereby reducing pain and inflammation while preventing inhibition of the homeostatic functions of prostaglandin E2.

Nutritional management

Essential fatty acids (omega-3 and omega-6) in the diet can play a role in the management of canine OA.

Fatty acids are incorporated into the cell membranes within the body and while both omega-3 and omega-6 fatty acids are converted to eicosanoid as part of the inflammatory cascade, omega-6 fatty acids are believed to promote the production of prostaglandins and leukotrienes, which are proinflammatory mediators and may contribute to increased inflammation within osteoarthritic joints (Innes, 2018).

Feeding a diet with a high ratio of omega-3:omega-6 fatty acids has been demonstrated to improve ability to rise from rest and ability to walk (Roush et al, 2010). Commercially available diets, specifically formulated to have a high omega-3:omega-6 ratio, are the most reliable way of ensuring appropriate dietary intake of these essential fatty acids without the additional calories that may come by simply adding supplements to a normal canine diet.

Additional analgesics

While NSAIDs should remain the first drug of choice in managing pain associated with OA, multiple other drugs are commonly used alone or in combination with NSAIDs.

Variable degrees of evidence support these and many are not licensed for use in canine patients or in combination with an NSAID, and this should be discussed with owners at the time of prescription, along with ensuring off-label drug use consent forms are signed. These should not be used as a substitute for licensed treatments for OA or seen as a lower risk option than using NSAIDs.

It is better to consider these as additional analgesics when traditional (licensed) analgesic options have failed or do not provide adequate pain relief.

Amantadine is the only drug with proven efficacy for use in refractory osteoarthritic pain in dogs when used as an adjunct to an NSAID (Lascelles et al, 2008). Amantadine is an NMDA-receptor antagonist (same class as ketamine) and has the potential to provide analgesia, as well as reversing some of the central sensitisation occurred due to the presence of chronic pain in patients with OA.

Central sensitisation is the phenomenon whereby chronic pain results in an increased perception of a noxious stimulus by the CNS (wind up). This is synonymous with hyperalgesia and has been demonstrated in dogs with hindlimb joint pain (Harris et al, 2018).

While amantadine is not licensed for use in veterinary patients and, therefore, must only be used appropriately in accordance with the cascade, it does at least have some evidence of efficacy.

Gabapentin acts on gamma-aminobutyric acid receptors in the CNS and may be beneficial for use in the treatment of neuropathic pain and in the reversal of central sensitisation.

Gabapentin is not licensed in any veterinary species and no peer-reviewed studies document its efficacy in the management of canine OA. Anecdotally, it is used as an adjunct analgesic in patients with refractory pain, but is likely to require prolonged treatment courses to be effective. Care should be taken to ensure patients receiving gabapentin chronically do not suddenly cease treatment, as this can result in seizure activity.

Paracetamol is licensed for short (five-day) periods following trauma. It is specifically contraindicated to be used concurrently with NSAIDs and, therefore, should be used with caution as an additional analgesic. While concurrent use of NSAIDs (ibuprofen) and paracetamol is commonplace in human medicine, until safety and efficacy studies are available for veterinary patients this combination should be avoided as defence of complications is difficult with the datasheet for veterinary licensed paracetamol formulations.

Tramadol has anecdotally become very popular for use in managing pain in dogs with OA, with a large portion of patients referred for OA receiving this as the sole analgesic. This trend occurred despite the drug not having a veterinary licence and little evidence to support its use. Tramadol has been shown to be ineffective for the treatment of joint pain in dogs with OA and its use in this instance should be discontinued (Budsberg et al, 2018).

Surgery

Arthrodesis (joint fusion) and arthroplasty (joint replacement) are both effective methods for managing chronic osteoarthritic pain in dogs. Total hip replacement has gained widespread acceptance with a consistently good outcome in the majority of cases (Liska and Israel, 2018).

Multiple replacement systems for the elbow are commercially available; however, the outcomes have not been as consistent, with one study reporting an unacceptable outcome in 24% of cases (De Sousa et al, 2016). A stifle joint replacement system is available, but is only performed in a small number of institutions in the UK.

BioMedtrix announced a tarsal joint replacement system and this is an exciting development for a joint that has previously only had arthrodesis as a salvage option (Acker, 2018).

Other treatments

Multiple other treatments are marketed for the treatment of OA, including pentosan polysulphate, intra-articular injections of platelet-rich plasma, nutraceuticals such as chondroitin and glucosamine, turmeric extract, acupuncture, extracorporeal shockwave therapy and low-level laser light therapy. However, these have not been discussed in this article as little evidence supports their use and client finances are better used on the proven effective treatments available.

Conclusion

Canine OA is a common disease encountered in both first opinion and referral veterinary practice. Conservative management (weight reduction, exercise modification and appropriate analgesics) should form the mainstay of treatment.

Tendencies to use unlicensed medications should be avoided until licensed medications have failed. Surgical options, including arthrodesis and joint replacement, are still considered salvage procedures for refractory joint pain and should be used when appropriate.