Exploring the 6 Types of Equine and Canine Arthritis

Arthritis is one of the most common causes of lameness and discomfort in horses and dogs. Whether it’s a seasoned polo pony showing signs of stiffness or an active dog slowing down on walks, arthritis is a diagnosis every Vetrehabber encounters.

But what exactly is “arthritis”? While it broadly refers to disease of the joints, arthritis comes in many forms—each with different causes, presentations, and management strategies. In this blog, we’ll explore the six primary types of arthritis, grouped into two overarching categories: inflammatory and non-inflammatory.

And, we’ll also unpack a fascinating paradox: if all arthritis involves inflammation, why are some types labelled “non-inflammatory”?

Let’s dive in.

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Inflammatory vs. Non-Inflammatory Arthritis: A Clinical Framework

Arthritis types are often grouped based on whether the primary driver of the disease is inflammatory (such as the immune system or infection) or non-inflammatory (such as wear, trauma, or blood in the joint). This classification helps clinicians choose the right diagnostic and treatment approach.

Non-Inflammatory Arthritis

Inflammation may be present, but it’s a secondary consequence of mechanical or traumatic joint damage.

Inflammatory Arthritis

Here, inflammation is the root cause, often due to infection, immune dysregulation, or chemical irritation from crystals.

The 6 Classifications of Equine and Canine Arthritis

Non-Inflammatory Arthritis

1. Osteoarthritis (OA)

Osteoarthritis is the most prevalent form of arthritis in both dogs and horses. It’s a progressive, degenerative disease characterized by the breakdown of articular cartilage, changes in subchondral bone, osteophyte formation, and varying degrees of synovial inflammation.

OA is often a final common pathway following trauma, instability, developmental disorders, or repetitive stress. In working animals like sport horses and active dogs, it’s a frequent cause of performance decline and chronic pain.

Despite being categorized as “non-inflammatory,” OA does involve low-grade, chronic inflammation that contributes to joint deterioration over time.

2. Traumatic Arthritis

Traumatic arthritis results from acute or cumulative injury to joint structures—such as synovium, ligaments, cartilage, or subchondral bone. This may include joint capsule strains, osteochondral fractures, or joint hyperextension injuries.

It often presents with joint effusion, pain on flexion, or acute lameness. If recognized early and managed well, traumatic arthritis can resolve or remain asymptomatic. But if ignored or reinjured, it can progress to osteoarthritis.

Common in performance animals (e.g., polo ponies, agility dogs), traumatic arthritis is mechanical in origin, and inflammation is a secondary response to tissue damage.

Osteoarthritis vs. Traumatic Arthritis: A Side-by-Side Comparison

3. Coagulopathic Arthritis

This lesser-known form of arthritis results from bleeding into the joint (hemarthrosis) due to clotting disorders or trauma in animals with impaired coagulation.

The presence of blood in the joint is highly inflammatory and toxic to cartilage. It disrupts the synovial environment, causing pain, swelling, and potentially long-term joint damage. Coagulopathic arthritis is rare, but should be considered in cases involving anticoagulant rodenticide exposure, clotting factor deficiencies, or significant joint trauma.

Here again, inflammation is present—but not immune-driven—so the classification remains non-inflammatory.

Inflammatory Arthritis

4. Immune-Mediated Arthritis

Immune-mediated arthritis is caused by systemic immune dysregulation. The immune system mistakenly targets the joint lining, leading to chronic inflammation, synovial thickening, and cartilage degradation.

In dogs, immune-mediated polyarthritis (IMPA) is the most common form and often affects multiple joints. It may be idiopathic or triggered by infection, neoplasia, or certain drugs.

Signs include joint swelling, stiffness (especially after rest), fever, and shifting lameness. Diagnosis typically involves joint fluid analysis and sometimes systemic testing. Treatment focuses on immunosuppressive therapy (e.g., corticosteroids, cyclosporine).

Though less common in horses, immune-mediated arthritis may present similarly.

5. Infective (Septic) Arthritis

Septic arthritis occurs when microorganisms invade the joint space, causing a rapid, destructive inflammatory response. It may follow penetrating trauma, joint injections, surgery, or hematogenous spread (especially in foals).

It is a medical emergency—if not diagnosed and treated promptly, it leads to rapid cartilage destruction and joint failure.

Diagnosis involves joint aspiration, cytology, and culture. Treatment includes aggressive lavage, systemic antibiotics, and often supportive rehab after infection control.

Though it can resemble traumatic arthritis early on, the presence of infectious organisms makes it definitively inflammatory.

6. Crystal-Induced Arthritis

Though rare in horses and dogs, crystal-induced arthritis is well-documented in veterinary medicine. Crystals such as uric acid (in breeds like Dalmatians) or calcium pyrophosphate dihydrate (CPPD) can accumulate in joints and irritate the synovium.

These crystals trigger a strong inflammatory reaction, causing swelling, pain, and joint dysfunction. Diagnosis requires synovial fluid analysis to visualize the crystals under microscopy.

This form of arthritis is more common in exotic species and geriatric patients, but should be kept in mind when ruling out causes of polyarthritis or persistent joint inflammation.

Wait—Isn’t All Arthritis Inflammatory?

Yes… and no. Here’s where clinical terminology and biological reality get a little tangled.

All arthritis involves some level of inflammation. That’s because:

• Cartilage breakdown products stimulate immune responses
• Synovial tissues react to injury or overload
• Inflammatory mediators like IL-1β, TNF-α, and MMPs are present in all arthritic joints

But from a clinical perspective, we categorize arthritis based on:

• The origin and intensity of inflammation
• Whether inflammation is primary (immune/infectious) or secondary (trauma/wear)

So:

• OA, traumatic, and coagulopathic arthritis are labeled non-inflammatory because inflammation is a consequence—not the cause.
• Immune-mediated, infective, and crystal-induced arthritis are inflammatory by nature, with immune or pathogen-driven inflammation leading the pathology.

In short: all arthritis is inflammatory, but not all arthritis is classified as inflammatory.

Why This Classification Matters

Understanding what type of arthritis we’re dealing with shapes every clinical decision:

✅ Diagnosis: Immune-mediated disease may need bloodwork and joint taps; trauma may need imaging

✅ Treatment: Immune arthritis calls for immunosuppressants, infectious arthritis needs antibiotics, and OA is best managed with anti-inflammatories, joint therapies, and rehab

✅ Rehabilitation: Knowing the root cause allows the rehab professional to tailor exercise, loading, and hands-on work appropriately

✅ Prognosis: Some types resolve with treatment; others, like OA, must be managed long-term

Conclusion

Arthritis isn’t one disease—it’s a spectrum. By recognizing the six major types of equine and canine arthritis and the underlying mechanisms, we can make smarter clinical decisions, tailor treatment, and give our patients the best chance at comfort and mobility.

Whether the trigger is trauma, immune misfire, or infection, the joint will respond. How we respond as professionals makes all the difference.

Further Learning Resources on Arthritis

• Guidelines for Treating Canine Arthritis Through the Stages of Progression
• Radioactive Tin117m for Elbow Osteoarthritis
• Integrative Pharmacology Applied to Osteoarthritis Pain Management – Part 1 and 2, Diane Grosjean
• Unlocking the Mystery of Polyarthritis in Dogs, Kara Amstutz
• A Simple Guide to Common Medications Used in Osteoarthritis, Hannah Capon
• Managing and Treating Osteoarthritis in the Canine Athlete, Matt Brunke
• Proposed Canadian Consensus Guidelines on Osteoarthritis Treatment Based on OA-COAST Stages 1–4
• The Role of Strengthening in the Management of Canine Osteoarthritis