An 8 year old castrated male Chesapeake Bay Retriever, presented to Cornell University Hospital for Animals Emergency Service for evaluation following an extra capsular cranial cruciate ligament repair of the right stifle at the referring veterinarian 3 weeks prior. He had escaped confinement one week postoperatively and returned home acutely lame again in the right hind leg. A draining tract at the incision site was observed a few days following this incident and the patient’s condition continued to deteriorate. Significant physical exam findings included a fever of 104.9F, tachycardia, tachypnea and multiple swollen joints. Diagnostic workup included a complete blood count, chemistry panel, 4DX test, urinalysis, urine culture, blood cultures, arthrocenteses (stifles and elbows), synovial fluid cytology and culture, and thoracic and limb radiographs. Based on the results of these diagnostic tests, the dog was diagnosed with septic polyarthritis and concurrent systemic sepsis. This paper uses this clinical case as a model to discuss septic arthritis as well as a brief overview of sepsis.