Dog Immune-Mediated Polyarthritis Diagnosis and Care

Immune-mediated polyarthritis causes painful joint inflammation in dogs and requires careful diagnosis to distinguish from infectious and erosive forms.

Key Facts

Immune-mediated polyarthritis (IMPA) is the most common inflammatory joint disease in dogs
Type I IMPA is idiopathic; other types are associated with infections, neoplasia, or drugs
Clinical signs include fever, joint pain, shifting lameness, and reluctance to move
Diagnosis requires ruling out infectious causes with joint fluid cytology and culture
Sterile joint fluid with non-erosive changes on radiographs characterizes idiopathic IMPA
Prednisone is the first-line treatment; many dogs require months of therapy with gradual taper
Relapses occur in approximately 30-50% of dogs, particularly if steroids are tapered too quickly

Welfare Considerations

IMPA causes significant pain that often goes unrecognized because joint swelling may be subtle. Affected dogs are frequently described as just acting stiff or quiet, masking the severity of their discomfort. Prompt diagnosis and adequate pain control during the inflammatory phase is critical for both welfare and long-term joint health.

What You Can Do

Seek veterinary evaluation for any dog showing fever combined with stiffness or lameness
Complete the full steroid taper as directed - stopping early is a common cause of relapse
Monitor for steroid side effects including increased thirst, urination, and weight gain
Schedule regular joint and bloodwork monitoring during the treatment period
Ask your vet about pain medications to use alongside steroids during flares