"Bailey", a two year-old female spayed Labrador Retriever, presented to the New York State College of Veterinary Medicine with the chief complaint of acute severe right hindlimb lameness. Her history included a two month period of mild lameness, which suddenly worsened five days prior to presentation at Cornell. A tentative diagnosis of cranial cruciate ligament rupture was made based upon history and physical exam findings. This diagnosis was confirmed by radiography and exploratory stifle arthrotomy. This report will emphasize the importance of early diagnosis and surgical exploration of the stifle joint to prevent irreversible degenerative changes.