Project Summary/Abstract Background: Symptomatic knee osteoarthritis (OA) affects over 14 million people in the US, ~ 70% of whom have meniscal tear. About 400,000 arthroscopic partial meniscectomies (APM) are performed for OA and meniscal tear annually. Although patients live with OA for decades, research on treatment of meniscal tear in patients with OA (physical therapy (PT) or APM) has focused on the first 2 years following treatment. Consequently, there has been little research on the effect of APM or PT on progression of pathologic changes in cartilage, bone, synovium, and other structures. The parent R01 aims to answer salient questions about the long-term outcomes in this patient population by conducting a 12-year follow-up of subjects in the MeTeOR (Meniscal Tear in OA Research) Trial. Due to the intervening gap in data collection between the original trial and the follow-up period, a number of methodological issues are expected to require addressing. The proposed supplement project will identify important variables and challenges for the follow-up analysis. Specific Aims and Project Methods: The proposed project will have 3 stages. (Stage 1) Conduct a systematic literature review of the relationships between meniscal tear treatments and OA, including identifying confounders, mediators, modifiers, and other key variables, and interview treating clinicians to understand their decision-making process for meniscal tear in OA. (Stage 2) Methodologic evaluation of similar trials with completed follow-up activities. Existing trials which have evaluated treatment strategies for meniscal tear in OA will be reviewed, with a focus on those that have completed five or more years of follow-up of trial participants. (Stage 3) Create a causal directed acyclic graph (DAG) which describes the full set of relationships between variables related to meniscal tear treatment and OA. Prepare and submit two manuscripts reporting the findings of stages 1 and 2. Anticipated Impact: The proposed project will provide key context for the design of the MeTeOR follow-up study to ensure the potential impact of bias on results can be minimized. In addition, this project will provide valuable training opportunities for the candidate, strengthen her research skills, and introduce her to the practical realities of clinical research.