Stifle osteoarthritis (OA) secondary to rupture of the cranial cruciate ligament is one of the most common causes of chronic pain in dogs and is currently treated with a wide variety of therapies; however, some dogs still suffer intractable pain. Intraarticular (IA) triamcinolone acetonide (TA) injection is commonly performed in humans and horses for relief of OA pain. There is evidence of a beneficial effect on articular cartilage in dogs with experimentally-induced stifle OA, and empirically, IA TA has relieved pain and improved quality of life in some dogs with naturally-occurring stifle OA. However, this procedure is not performed routinely in dogs, partly due to concerns about systemic absorption and resultant adrenocortical suppression and iatrogenic hyperadrenocorticism (HAC). Before evaluating efficacy at relieving pain and effects on articular cartilage in client-owned dogs with naturally-occurring OA at the Cornell University Hospital for Animals, it is imperative that the systemic effects and safety of the procedure are determined. The first aim of the proposed study is to determine if IA injection of TA suppresses the adrenocortical axis by performing an adrenocorticotropic hormone (ACTH) stimulation test before and at intervals after injection. The second aim is to determine if IA injection of TA increases serum alkaline phosphatase (ALP) activity, a reliable indicator of HAC, by performing a liver panel before and at intervals after injection. The third aim is to determine if IA injection of TA causes other clinicopathologic abnormalities consistent with iatrogenic HAC by evaluating a complete blood count (CBC), the liver panel, and urine specific gravity (USG) before and at intervals after injection. This study will consist of two phases. Six healthy, adult, purpose-bred dogs will receive each of two treatments in random order,  a lower dose or a higher dose of TA injected into a stifle joint under sedation. The day before each injection, a baseline CBC, liver panel, USG, and ACTH stimulation test will be performed. One, 7, 14, 28, 42, 63, and 84 days after each injection, these tests will be repeated, with 1 month allowed between the end of the first phase and the beginning of the second phase. Baseline values will be compared to values at each post-injection time point utilizing the Kruskal-Wallis test with Dunn’s post hoc analysis. Data collection will be completed in approximately 7 months, and, if started during the summer of 2018, will be finished well before Dr. Gamble’s residency ends in July, 2019.