ABSTRACT Clinical Data Collection and Management Core Knee osteoarthritis (OA) is among the world's most disabling diseases, and it accounts for a substantial percentage of the increase in disability life years. The Multicenter Osteoarthritis (MOST) Study has made major contributions to our understanding of the course of OA and identification of risk factors for its incidence and progression. Beginning in 2003, the MOST initially enrolled 3026 participants with or at high risk of knee OA. In the most recent phase (MOST3), an additional 1525 participants who were slightly younger and unlikely to have advanced disease were enrolled. Despite the insights provided by the previous phases of MOST, there are still no treatments available that slow progression of OA. The next phase (MOST4) focuses on three major scientific projects that address key gaps in knowledge in OA. These projects include: Impaired Exercise-Induced Hypoalgesia (Project 1); Synovial Fluid Proteomics (Project 2); and Intra-articular Mineralization (Project 3). These projects will be supported by four Cores – the Administrative Core, the Imaging Core, the Analysis Core, and the Clinical Data Collection and Management Core (CDCMC). The overarching goal of the CDCMC is to ensure the success of the MOST projects by providing an outstanding infrastructure for visit enrollment, study procedures and data collection, and longitudinal ascertainment of critical outcomes. This core includes the Coordinating Center (led by Peggy Cawthon at UCSF) and the MOST clinical centers: University of Iowa (UI clinic center lead: James Torner) and University of Alabama, Birmingham (UAB clinic center lead: Cora E. Lewis). Specially, the aims of the CDCMC are to: 1) To enroll 2143 existing MOST participants, and 150 newly recruited participants from underrepresented racial and ethnic minority groups, for the MOST4 V1 examination (2293 total), and follow those participants for the MOST4 V2 examination, 2) Ensure the collection of high-quality research data and specimens, 3) To maintain a high rate of retention of study participants and complete ascertainment of study outcomes, 4) To ensure the safety of participants and to meet regulatory standards, 5) Collect, clean, document and integrate MOST data across all projects and cores.