Currently, there is no cure for osteoarthritis (OA). The treatments that are available, aim to reduce pain levels, but are often unsuccessful and also have undesirable side effects. In clinical trials that test pain relief medication, we use a dummy treatment called a placebo, which often looks like the real tablet or gel but doesn’t contain any drug. Half the people in the study will get the drug treatment and half will get the placebo but everything else, including how often they are seen by the researchers, what information they are given or what measurements are taken, is exactly the same. In trials of OA treatments, around 75% of the pain relief benefit can be put down to a placebo response rather than the specific effect of the medication. This response varies greatly from patient to patient. By analysing individual patient data from trials of osteoarthritis treatments, we will compare the characteristics of those people who responded to the placebo treatment compared to those who did not. We hope to be able to identify a subgroup of people with osteoarthritis who are most likely to respond to placebo and to be able to identify factors that will predict a response.