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. Two especially salient questions remain unanswered about the long-term outcomes in this patient population, and both will be addressed in this proposed 12-year follow-up of subjects in the MeTeOR (Meniscal Tear in OA Research) Trial. First, our preliminary data from MeTeOR, which compared outcomes of APM and PT, suggest APM is associated with more rapid structural progression through 5 years. It is critical to determine whether these effects of APM on OA progression are borne out with longer follow-up, as they are essential for informed discussions about benefits and drawbacks of APM and nonoperative therapy. A more profound research gap is the uncertain clinical interpretation of structural changes on MRI. While clinicians and investigators assume that rapid structural progression of OA results in more severe pain over the long term, there is scant evidence supporting this claim. MeTeOR subjects underwent MRI at baseline, 18-, and 60-months following enrollment, providing a unique opportunity to assess 12-year clinical consequences of structural progression. We propose the following aims: 1. Conduct 12-year follow-up of MeTeOR subjects to characterize the extent of cartilage damage over 12 years and identify factors, including treatment with APM vs. PT, associated with more rapid progression. 2. Assess whether the extent of progression in structural damage over the first 5 years post-treatment in persons with OA and meniscal tear predicts worse symptoms and functional status at 12 years. Successful completion of these Aims will provide clinicians and their patients with crucial data to facilitate informed decisions about treatment for meniscal tear and OA. This work will also test the foundational assumption that structural progression in OA leads, ultimately, to pain and functional limitation.