Osteoarthritis (OA)

Osteoarthritis (OA)

TABLE OF CONTENTS

What is Osteoarthritis (OA) ?

Secondary Osteoarthritis (OA) is a chronic inflammatory joint disease which can be a single or multi joint problem. It's often referred to as Degenerative Joint Disease (DJD) in the equine world.

Secondary OA is very common in dogs and describes a condition caused by an identified primary cause that leads to secondary OA developing.

It's characterised by the degeneration and remodelling of synovial joints which leads to impaired mechanical function and pain, negatively impacting on the dog's mobility and daily activities.

Primary OA is an insidious condition seen in older people and is rare in dogs whereas Secondary OA is common see in dogs and humans.

Causes of secondary OA include;

  1. Heritability, for example, leading on from joint disease such as hip dysplasia (HD) or elbow dysplasia (ED)
  2. Poor conformation
  3. Trauma, following on from injury or fracture disease
  4. End stage of many canine conditions
  5. Excessive and repetitive forces to the musculoskeletal system (MSK) due to athletic and working roles
  6. Joint infections, for example Lyme Disease

The proportion of the canine population which develops the chronic, progressive condition called OA, is unknown.

OA can develop at any age, however it is considered to be a disease of 'ageing' in dogs. The most commonly reported affected joints are the hips, stifles and elbows.

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Timeline differences between humans and dogs.

It becomes a more significant problem in later life and the disease is typically diagnosed when the dog's mobility is seriously affected.

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It is suggested that more than 50% of diagnosed dogs are aged from 8 to 13 years.

It's understood that mechanical stress induces the changes in biochemical factors within the affected joint / s which then leads to articular degradation.

Joints commonly affected by secondary Osteoarthritis (OA).NB knee = stifle.
Joints commonly affected by secondary Osteoarthritis (OA).NB knee = stifle.

The disease process limits the amount of protein released from the cartilage cells responsible for repairing the joint cartilage. The continuing breakdown of the cartilage results in its destruction, leading to friction between the bones โ†’ inflammation โ†’ thickening of the soft tissues โ†’ decrease in the joint range of motion (ROM).

The end result of degenerative joint or inflammatory disease is known as ankylosis; which is the fusion of the joint following new bone production.

Most forms of arthritis lead to a loss of bone or cartilage that results in changes in the shape of joint and articular opposition. This results in a deterioration of joint function and therefore mobility.

Breeds prone to OA

Osteoarthritis affects 1 in 5 dogs (20%) and its prevalence increases with age.

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Certain breeds are more predisposed and it has an impact on the larger sized dog breeds. It's seen more in large to giant breeds plus certain lifestyles can contribute to its development, e.g. hard repetitive training, over exercise or long-term obesity.

Any breed of dog can develop OA and a few breed examples prone to OA include;

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Pathogenesis

OA most commonly affects the synovial joints, in particular the ball and socket (hip and shoulder) and complex hinge joints (elbow) in the dog.

The synovial joint capsule contains synovial fluid which provides nutrients, lubrication and a cushion for the articular hyaline cartilage. The articular cartilage reduces friction allowing a smooth gliding motion for the bone ends, leading to efficient movement patterns.

The hyaline cartilage contains a high content of Type II Collagen and distributes pressure from the load over the subchondral bone, which acts as a shock absorber.

In a healthy synovial joint there is a symbiotic balance between the cells, however the balance is disrupted in OA by the overproduction of osteoblasts which causes pain and swelling.

When the cartilage is damaged as in OA, the response is an increased production of synovial fluid in order to compensate for the diseased joint, leads to the joint distended, causing further pain.

"OA has multiple causes and risk factors; however, once the cartilage is lost, the joint fails."

OA is a progressive disease which consists of 4 stages.

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Stage 1: Minor bone spurs begin to develop and the cartilage matrix begins to break down. Cartilage lesions disrupt the function of cartilage which increases friction and inflammation in the joint, resulting in pain.

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Stage 2: This mild stage is when there is erosion of the bone due to the cartilage lesions, leading to new bone growth / bone spurs, which affect normal joint movement.

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Stage 3: This moderate OA is when the cartilage between the bones thins out and loses it's cushion effect. There is narrowing of the space between the bones leading to grinding between the adjacent subchondral bones and evident inflammation occurs.

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Stage 4: This final stage is severe OA. The joint space is significantly reduced, the cartilage is almost gone and joint mobility is reduced greatly.

"Early diagnosis of OA is key to prevent further damage to the joint and alleviate pain, joint stiffness, reduced ROM and lameness"

OA is an extremely complex and progressive disease. It initially focuses on moving joints but eventually affects the dog globally.

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Left-normal hip joint, femoral head fitting snugly into the acetabulum + smooth bone edges. Right-femoral head does not fit into acetabulum + shows signs of OA.
Arthritic elbow joint. What changes can you see around the joint?
Arthritic elbow joint. What changes can you see around the joint?

Arthritic stifle joint. Identify the bones you can see in this X-ray.
Arthritic stifle joint. Identify the bones you can see in this X-ray.

Look at the shoulder joint above and identify what other conditions may affect this ball and socket joint.
Look at the shoulder joint above and identify what other conditions may affect this ball and socket joint.

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(a) lateromedial view of the shoulder, (b) cranial caudal view of the stifle, (c) lateral view of the stifle.

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Degeneration of the normal joint structures.

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Pain causes reduced loading of the joint and limb.

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Surrounding muscles, tendons + ligaments become weak.

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Compensatory static + dynamic patterns develop causing further pain.

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The brain becomes more aware of the constant pain + magnifies it.

OA may be classified as primary or secondary depending on the aetiology.

Primary OA is very rare in dogs and associated with generalised ageing and degeneration of the cartilage within the joints, with unknown reason.

Secondary OA occurs in response to associated joint instability; abnormal loading of the articular cartilage; developmental or anatomic abnormalities; or in response to other joint disease; infection / immune-mediated inflammation.

OA can be divided into developmental or acquired

Developmental

These are dogs that are genetically predisposed to having abnormally formed joints, which becomes more apparent as the dog grows.

Certain breeds are more likely to be predisposed such as Labrador Retrievers and Golden Retrievers. Abnormalities within the joints means poor biomechanical function resulting in damage to the structures within the joint.

Inflammatory changes occur, leading to signs of OA. The changes within the joint structure can be mild to severe which directly influence the severity of the signs, plus the age at which they appear.

Excessive weight, inappropriate exercise, having to negotiate slippery floors and continued access to stairs lead to excessive forces through affected joints and impact the evident clinical signs.

Acquired

This is where circumstances have lead to the disease development.

Traumatic injuries to a joint, immune-mediated disease targeting a joint or infections within a joint are all likely causes of acquired OA.

Clinical Signs

OA is a chronic, painful disease and is one of the most common conditions in dogs. It's not a "one step disease", affecting single or multiple joints and can severely impact on the dog's quality of life.

Lameness is the usual presenting sign and is often reported to be chronic, with an insidious onset and a progressive deterioration is seen over time.

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Lameness and stiffness often follow periods of rest in the early stages of the disease.

As the disease progresses, stiffness following rest becomes more pronounced and the dog is often reported to "warm out" of the stiffness.

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Many joints affected by OA may not show clinical disease in the early stages.

  • Pain
  • Lameness
  • Cold / damp increases lameness
  • Slowing down
  • Not playing with toys
  • Decreased appetite
  • Morning stiffness
  • Reluctance to exercise
  • Stiffness after exercise
  • Difficulty getting up or lying down
  • Difficulty toileting
  • Sleeping more
  • Reluctance to jump
  • Difficulty ascending / descending stairs
  • Abnormal gait
  • Reduced athletic performance
  • Decrease joint range of motion (ROM)
  • Crepitus apparent on ROM
  • Muscle atrophy
  • Poor mobility
  • Change in demeanour
  • Swollen joints
  • Licking joints
  • Postural changes
  • Pacing at night
  • Slower transitions or postural transfers
Clinical signs vary, with acute "flare ups" occurring sometimes.

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Dogs don't always overtly show signs of pain. Always look for the subtle changes in the dogs daily routine and behaviour.

"Most canine patients do not vocalise from their OA pain. Many pet owners do not believe their pet is in pain if it does not vocalise".

Diagnostic Tests

  • Radiography (x-rays); is an imaging technique using X-rays, gamma rays, or similar ionising radiation and non-ionising radiation to view the internal form of an object. This may show new bony deposits (osteophytes) particularly on the articular margins and in association with attachments of the joint capsule and ligaments.
  • In chronic cases you will see sclerosis of the subchondral bone, therefore a loss of cartilage. Narrowing of the joint space also indicates loss of cartilage and periarticular calcification is commonly seen in remodelling of the joint. Occasionally you can see bone cysts and bone attrition

Xray machine
Xray machine
  • Blood Tests; a multitude of blood tests can be used to determine the degree of inflammation in the joints from arthritis and can highlight any chronic diseases. Can also be used as a baseline for monitoring the effects of medications on the body.
  • Urine Samples; can highlight any chronic diseases and can be used as a baseline for monitoring the effects of medications on the body.
CT scanner
CT scanner

  • Computed Tomography (CT); is a medical imaging procedure that uses computer-processed combinations of many X-ray measurements taken from different angles to produce cross-sectional images (virtual "slices") of specific areas of a scanned object
  • Joint Fluid Collection; if multiple joints are affected, joint fluid collection can rule out other joint conditions; septic arthritis (bacterial infection of the joint) or immune-mediated arthritis (this is where the dog's own immune system attacks the joint)

OA Treatment + Management

Owners need to be counselled and supported to understand that OA is likely to be a lifelong process with flare-ups that may increase in severity and frequency as the dog ages.

The best approach to these cases often involves a balancing act between physiotherapy, hydrotherapy, medical management, weight management and surgery.

Conservative (non-surgical)

Effective pain management

Adequate rest; to ensure reduced forces through the joint however, it is essential to have controlled exercise to maintain muscle tone, mass and function, plus prevent joint stiffness.

Acute flare ups must have REST.

Anti-inflammatory medications; to control signs of arthritis, including inflammation, swelling, stiffness and joint pain.

Nutraceuticals; glucosamine and chondroitin help decrease joint inflammation and improve the bodyโ€™s ability to repair and strengthen tissues.

Disease modifying osteoarthritic agents; this can be given either as a muscle injection (PSGAG) or intra-articular (into the joint) injection (corticosteroids, platelet-rich plasma, hyaluronic acid, and stem cell). More research is necessary to ascertain the benefit of disease-modulating agents.

Devising a treatment plan for each dog based on their specific assessment findings is imperative to deliver an effective conservative treatment.

Many different physical therapies and electrotherapies can be utilised and avoid a prescriptive protocol and application as this limits outcomes and progress. There is no "one fix for all" with this complex condition.

A holistic MDT approach employing conservative treatment strategies may include;

Physiotherapy, Hydrotherapy, Acupuncture; Pulsed Magnetic Field Therapy, Laser Therapy, Herbal Therapy, Homeopathy, Chiropractic, Osteopathy, Galen Myotherapy, TTouch

Important conservative treatments embracing a multimodal approach;

  • Pain management
  • Bodyweight control + monitoring
  • Exercise modification
  • Nutritionally balanced diet
  • Nutraceuticals
  • Home environment adaptations
  • Physiotherapy
  • Hydrotherapy
Canine Arthritis Management CAM

Surgical Management

Most patients with osteoarthritis can be managed with a combination of medical measures and other conservative measures. However, for patients where the response is poor, surgical management should be considered.

For canine surgical management of OA, the approach is a total joint arthroplasty. Canine total hip replacement (THR) is currently the most commonly performed and reliable, with procedures in place for stifle and elbows joint replacements which have varied success.

Due to the relative success of canine hip replacements achieved in more than 90 per cent of cases (Allen 2012), this procedure is now performed at a much earlier stage than recommended. Young dogs with pain associated with OA which is affecting their quality of life may be suggested for THR surgery to allow these dogs to lead a normal life.

Stifle and elbow replacements are technically more challenging and remain salvage procedures where all else has failed.

In some cases, total joint replacement is not possible and arthrodesis may be a suitable alternative. This leads to a pain free joint for the dog, however it produces a rigid joint and so is better suited to the low motion joints such as the carpus and tarsus.

Elbow, stifle and shoulder arthrodesis is possible, but is technically challenging and the dog does have limited function. Arthrodesis of the coxofemoral joint is not possible, so a femoral head and neck excision should be performed if a THR is not possible.

In extreme cases amputation is considered but has a massive impact on the dog and it is imperative to ensure the patient will still be able to ambulate following surgery.

Euthanasia is used in some extreme cases where the welfare of the animal is a concern and treatment options have failed or are not affordable.

OA joint pain doesn't have to be the normal part of a dog getting older.

References

Bland, S.D. Canine osteoarthritis and treatments: a review. Veterinary Science Development. 2015; Vol 5, pp.5931. Davies, M. Practical management of canine arthritis. Vet Times, Companion Animals, Vets. Jan19th 2015.

Hielm-Bjรถrkman, A. et al. Evaluating Complementary Therapies for Canine Osteoarthritis Part I: Green-lipped Mussel (Perna canaliculus). Evid Based Complement Alternat Med. 2009, 6 (3), pp. 365-73.

Pettitt, R.A., German, A.J. Investigation and management of canine osteoarthritis: In Practice 2015, 37, pp.1-8.

Sandersoln, R.O. et al. Systematic review of the management of canine osteoarthritis. Veterinary Record, 2009, 164, pp. 418-424.

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