Polyarthritis in dogs and cats as a specific form of painful joint disease affecting multiple joints requires specific attention. 

The same applies for canine immune mediated polyarthritis IMPA where the underlying issues triggering the joint disease can be more severe than the actual joint inflammation, pain, and swelling.

In dogs with polyarthritis, especially if immune mediated, the changes although occurring within the joints are not the same as in dogs with osteoarthritis. 

Immune mediated polyarthritis in the canine equivalent of rheumatoid arthritis in humans. Sadly, the condition is quite complex and the prognosis for dogs with polyarthritis usually depends on the underlying disease and presence of complications. 

What is Polyarthritis in Dogs?

The term polyarthritis in dogs translates to joint inflammation that affects multiple joints in the body. In simple words, polyarthritis is a joint disease that affects multiple joints.

Dogs with polyarthritis have inflamed, swollen, and painful joints which cause lameness and reluctance to walk.

Immune-Mediated Polyarthritis in Dogs

Immune-mediated polyarthritis (IMPA) is an immune-mediated disease that develops when the body’s immune system triggers an abnormal immune response toward multiple joints.

There are two possible scenarios:

  • The immune system may overreact due to an infection
  • The immune system misidentifies the joint tissues as foreign

Canine Immune-Mediated Polyarthritis Classification

Immune-mediated polyarthritis in dogs and cats is a type III hypersensitivity in which immune complexes start accumulating in the joint’s synovial fluid. This triggers a disease process in which neutrophils are attracted and gathered in the joint fluid. These forms are known as non-erosive.

Some immune-mediated polyarthritis IMPA forms include type IV hypersensitivity reactions and manifest with T cell accumulation in the synovial fluid. Once the T cells accumulate in the synovial fluid they start attacking the joint cartilage.

If the inflammatory joint changes are accompanied by cartilage damage, immune-mediated polyarthritis is labeled as erosive.

In the past, immune-mediated polyarthritis in dogs was classified into four categories:

  • Type 1 IMPA – canine idiopathic polyarthritis
  • Type 2 IMPA – triggered by an infection that is not related to the joints
  • Type 3 IMPA – triggered by gastrointestinal disease
  • Type 4 IMPA – triggered by neoplasia.

Today, we classify IMPA as:

  • Primary IMPA – refers to idiopathic cases with unknown underlying disease
  • Secondary (reactive) IMPA – when the underlying disease can be identified and occur outside the joints.

Causes of Polyarthritis

In dogs and cats, the immune system is responsible for protecting the body from infections by attacking the threat. In cases of polyarthritis, the immune system is tricked into attacking the body’s joint tissues.

The culprit responsible for tricking can be a joint inflammation or another disease process within the joints or an infectious disease elsewhere in the body.

Causes of Non-Immune Mediated Polyarthritis

Non-immune mediated polyarthritis in dogs can be caused by:

  • Degenerative joint disease or osteoarthritis
  • Trauma
  • Neoplasia
  • Infectious diseases (bacterial, fungal, viral, and vector-borne diseases)

Causes of Immune-Mediated Polyarthritis

The causes of immune-mediated polyarthritis can be classified as primary and secondary.

  • Primary immune-mediated polyarthritis
    • Non-erosive immune-mediated polyarthritis
      • Idiopathic (type I)
      • Systemic lupus erythematosus
      • Breed-associated (Shar-pei, Akita)
      • Polyarthritis-polymyositis
      • Steroid-responsive meningitis-arteritis
      • Polyarteritis nodosa
      • Sjögren’s syndrome
      • Juvenile cellulitis
    • Erosive immune-mediated polyarthritis
      • Rheumatoid arthritis
      • Breed-associated (greyhound)
      • Idiopathic
  • Secondary (reactive) immune-mediated polyarthritis
    • Systemic or non-joint infection (type II)
    • Gastrointestinal disease (type III)
    • Non-joint neoplasia (type IV)
    • Systemic or non-joint inflammatory disease
    • Medication-related
    • Vaccine-induced.

Specific Types of Immune-Mediated Polyarthritis

Systemic lupus erythematosus is an autoimmune disease that affects multiple organs and affects medium and large-sized, middle-aged dogs. The clinical signs of systemic lupus erythematosus include:

  • Intermittent polyarthritis (painful and swollen joints)
  • Hemolytic anemia
  • Polymyositis
  • Skin lesions
  • Fever of unknown origin
  • Oral ulcerations
  • Glomerulonephritis
  • Lymphadenopathy

The diagnosis and treatment of systemic lupus erythematosus are challenging and the prognosis is guarded.

Breed-specific polyarthritis is a unique IMPA syndrome occurring in Akitas and Shar Peis. In Akita, immune-mediated polyarthritis develops simultaneously with meningitis or other inflammations.

In Shar Peis, this type of IMPA is popularly known as Shar Pei fever or swollen hock syndrome. It manifests with joint swelling and fever.

Steroid-responsive meningitis arteritis (SRMA) is an IMPA form prevalent among young, male, large-sized dog breeds like Bernese Mountain Dogs, German Shorthaired Pointers, and Weimaraners. The main clinical sign is back pain.

Idiopathic immune-mediated polyarthritis is a specific erosive IMPA type occurring in small breed dogs between the age of two and six. It manifests with stiffness, intermittent lameness, and swelling of one or multiple joints.

Vaccine-associated polyarthritis is an unusual IMPA form occurring in dogs around 30 days post-vaccination. In dogs with this IMPA form, distemper antigens are present in joint fluid. However, the exact mechanism is unknown, and usually, the condition is self-limiting.

Symptoms of Polyarthritis

A study by Clements DN, Gear RN, Tattersall J, et al. Type I immune-mediated polyarthritis in dogs: 39 cases (1997-2002), JAVMA and a study by Stull JW, Evason M, Carr AP, et al. Canine immune-mediated polyarthritis: clinical and laboratory findings in 83 cases in western Canada (1991-2001). Can Vet J confirm that in dogs with polyarthritis the most common clinical signs include:

  • Reluctance to walk
  • Altered gait or lameness
  • Multiple swollen and painful joints

Based on a study by Rondeau MP, Walton RM, Bissett S, et al. Suppurative, nonseptic polyarthropathy in dogs. J Vet Intern Med, polyarthritis in dogs can sometimes manifest with spinal pain.

However, according to a study by Bennett D. Immune-based non-erosive inflammatory joint disease of the dog. 3. Canine idiopathic polyarthritis. J Small Animal Pract, IMPA does not cause swollen joints or pain in 8 to 40% of the cases.

The lack of visible joint-related clinical signs makes the diagnosis of IMPA quite challenging.

According to a study by Dunn KJ, Dunn JK. Diagnostic investigations in 101 dogs with pyrexia of unknown origin. J Small Anim Pract, a dog with polyarthritis lacking obvious joint pain and swelling signs usually show:

  • Fever of unknown origin
  • Lethargy
  • Decreased appetite
  • Vomiting
  • Diarrhea.

The presence of fever is also shown in a study by Battersby IA, Murphy KF, Tasker S, et al. Retrospective study of fever in dogs: laboratory testing, diagnoses, and influence of prior treatment. J Small Anim Pract.

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Diagnosing Polyarthritis in Your Dog

When a dog has clinical signs like lameness, abnormal gait, and painful and swollen joints, the vet will start by performing a full body examination to check for potential underlying issues.

The diagnosis of IMPA is based on three red flags:

  • Multiple joints inflammation
  • Lack of infection occurring within the joint
  • Positive response to therapy with immunosuppressants.

In dogs with polyarthritis or IMPA, the changes occur within joint fluid. Therefore, a conclusive diagnosis is made through an arthrocentesis – taking small synovial joint fluid samples and analyzing the synovial fluid content (blood cell counts and proteins) and joint fluid characteristics.

In a chapter on Arthrocentesis in Taylor SM, ed. Small Animal Clinical Techniques. St. Louis, MO: Saunders, recommends taking synovial fluid samples from at least three joints, including the carpus or tarsus. The carpus and tarsus are most frequently affected when a dog develops IMPA.

Taking a synovial joint fluid sample is painful, and in dogs and cats, it is usually performed under sedation.

As shown in a study by MacWilliams PS, Friedrichs KR, Laboratory evaluation and interpretation of synovial fluid, Vet Clin North Am Small Anim Pract, in dogs with healthy joints, the synovial joint fluid contains less than 3000 white blood cells per microliter (primarily mononuclear cells) and less than 2.5 grams per deciliter of protein.

Dogs with immune-mediated polyarthritis have significantly higher blood cell counts (mostly neutrophils) and higher protein concentrations.

Other baseline tests for dogs with IMPA include blood and urine tests – complete blood count, serum biochemistry panel, and urinalysis. The blood and urine tests in canines with IMPA usually show:

  • Leukocytosis – increased white blood cell counts
  • Mild anemia – decreased red cell count
  • Hypoalbuminemia
  • Mildly increased alkaline phosphatase
  • Elevated protein to creatinine urine ratio

Specific blood tests and infectious disease screening are recommended for dogs with high exposure risks to vectors or other dogs with vector-borne diseases.

If the joint fluid and blood tests are not conclusive, the veterinarian will order chest x-rays, abdominal x-rays, abdominal ultrasonography, and x-rays of multiple joints.

Even if dogs present with clearly swollen and painful joints, the vet must look at the bigger picture and evaluate the situation in detail which often requires additional tests, including the above-mentioned synovial fluid samples, blood tests, complete blood counts (especially white cell counts), x rays of the joints and other organs, and infectious disease screenings.

Grobman M, Outi H, Rindt H, et al. in their study Serum thymidine kinase 1, canine-C-reactive protein, haptoglobin, and vitamin D concentrations in dogs with immune-mediated hemolytic anemia, thrombocytopenia, and polyarthropathy published in the J Vet Intern Med suggesting measuring the C reactive protein levels as standard procedure in dogs with IMPA.

The importance of the C reactive protein is also supported in a study by Foster JD, Sample S, Kohler R, et al. Serum biomarkers of clinical and cytologic response in dogs with idiopathic immune-mediated polyarthropathy. J Vet Internal Medicine.

This parameter can be evaluated through a simple blood test and is vital when differentiating between IMPA and osteoarthritis.

Polyarthritis Treatment Options

The veterinary internal medicine branch dealing with joint issues and canine immune-mediated polyarthritis gives the following polyarthritis treatment protocol:

  • Analgesia – includes opioids, gabapentin, and amantadine. The analgesic drug of choice for joint pain is NSAIDs. However, they are not recommended for dogs with IMPA.
  • Doxycycline trial – a study by Littman MP, Goldstein RE, Labato MA, et al. ACVIM small animal consensus statement on Lyme disease in dogs: diagnosis, treatment, and prevention. J Vet Intern Med supports the claim that in dogs with polyarthritis due to vector-borne disease doxycycline reduces clinical signs like swollen joints and painful joints.
  • Immunosuppressive medications – to set the immune system to default programming and suppress its efforts of attacking the joint tissues
  • Underlying condition – treating the underlying IMPA trigger is vital. However, as mentioned in dogs with polyarthritis, sometimes the IMPA trigger cannot be identified.

Holistic Ways to Help Your Dog

You can help your dog’s swollen and painful joints by using CBD oil. The use of CBD oil in the veterinary medicine field is relatively new but its results are quite promising.

Just like CBD oil can help people with rheumatoid arthritis it can be beneficial in dogs with polyarthritis.

These are some of the CBD oil features dogs with polyarthritis can benefit from:

  • Helps maintain a normal inflammatory response in the body
  • Supports the immune system
  • May help with discomfort associated with normal daily exercise and activity
  • Can help with occasional discomfort
  • Can help with occasional stiffness and soreness
  • Supports bone and joint health
  • Provides connective tissue support
  • Promotes the body’s innate resistance to pathogens.

You can give your dog CBD products for pets in the form of oral tinctures or CBD-infused treats.

Heat therapy (heating pads or blankets) and low-impact exercise (swimming) are also recommended in IMPA patients.

Our Final Thoughts

Joint pain and fever of unknown origin in dogs are always a reason to see the vet and have the clinical signs investigated in detail.

Unlike most degenerative joint changes that come with age, immune-mediated polyarthritis IMPA can occur in all dogs regardless of age and triggers a specific set of changes occurring in the synovial fluid of the joints.

This is because the disease is based on immune system malfunction rather than natural wear and tear of the joints.

Just like people with rheumatoid arthritis, managing dogs with polyarthritis or immune-mediated polyarthritis IMPA can be challenging. This is because regular treatment options often have side effects more severe than the initial swollen and painful joints.

Frequently Asked Questions

What is the treatment for polyarthritis in dogs?

In dogs, the treatment for polyarthritis includes pain management, immunosuppressive drugs, and holistic approaches like CBD oil, heat therapy, and low-impact exercise (swimming).

What is the treatment for polyarthritis?

Polyarthritis can be managed with immunosuppressive drugs. However, the underlying condition that triggered the polyarthritis needs to be addressed too.

How is polyarthritis diagnosed?

The basic diagnostic procedure for IMPA is arthrocentesis – taking small synovial fluid samples from several joints and analyzing their content. Additional blood and urine tests, as well as x-rays and infectious disease screening tests, are also helpful.

Is polyarthritis in dogs hereditary?

There are breed-associated IMPA syndromes in certain dogs like Weimaraners, Beagles, German Shorthaired Pointers, Akitas, Shar-Peis, Bernese Mountain dogs, Boxers, and Spaniels.