Project Abstract Despite the high global prevalence of knee osteoarthritis (OA), treatment options have been limited to symptom management and total joint replacement in large part because the mechanisms driving knee OA remain poorly understood. Genome-wide association studies (GWAS) suggest that non-coding genetic variation is a major contributor to knee OA disease-risk; however, the LD structure of human genomes, the long-range nature of transcriptional regulation, and the lack of genome-editable and biologically accurate systems in which to study OA have created a bottleneck that hinders our ability to translate GWAS findings into new treatments. The overall objective of this proposal is to identify putative causal knee OA risk variants, map them to their target genes, and quantify their phenotypic impact in chondrocytes. We will identify regulatory regions activated in response to cartilage degradation (Aim 1), map regulatory loci and GWAS variants to their target genes (Aim 2), and quantify the phenotypic impacts of knee OA-associated variants using an ex vivo model of the chondrocyte OA phenotype (Aim 3). This work will break down existing barriers in knee OA genetics, improve our mechanistic understanding of knee OA, and provide new risk genes for further study and therapeutic development.