The radiographic prevalence of osteoarthritis (OA) in cats is estimated to be as high as 90% of the population. However, radiographic evidence has a very poor correlation with clinical signs (either pain or dysfunction). The reasons behind this poor correlation include practical ones such as the fact that cats hide “pain” as well as the more clinical issues such as the lack of specific and validated tools identifying and quantifying such pain or dysfunction. There is currently one validated multifactorial scale for identifying acute pain in the cat but there are no good tools for chronic pain. The gold standard for identification of OA in the cat is currently through radiography. Obtaining full radiographs of cats involves deep sedation or full general anaesthesia which is not ideal for many situations. The goal of this study is to develop a blood test biomarker for osteoarthritis in order to diagnose OA earlier, treat OA earlier, and possibly even to use the biomarker as a gauge of the effectiveness of treatment. The advantage of a blood test, especially if used as a screening tool, would eliminate the need for sedation or anaesthesia along with decreasing costs for the owner.