An 8-year-old, spayed female Husky dog was presented to the Cornell University Hospital for Animals Emergency Service for evaluation of an acute exacerbation of a one month lameness. The patient had escaped her yard and was found non-ambulatory. Significant physical exam findings at Cornell included elevated respiratory rate, increased right shoulder range of motion during abduction, mild to moderate bilateral elbow and hock effusion, severe shoulder and hind limb reactivity on palpation, and regurgitation. Diagnostics included a complete blood count, chemistry panel, urinalysis, synovial fluid cytology and culture, thoracic radiographs, abdominal radiographs, pelvic radiographs, right shoulder radiographs, right carpal radiographs, and bilateral tarsal radiographs. Based on the results of these diagnostic tests, the dog was diagnosed with idiopathic immune-mediated polyarthropathy (IMPA) and severe bilateral tarsal subluxation. This case report provides a brief overview of the diagnosis and management of idiopathic IMPA.