Magnetic resonance (MR) imaging is a 3D imaging technique that has recently begun to permit direct delineation of cartilage structure. This chapter summarizes current methodology for the morphological (e.g., volume, thickness) and compositional imaging of cartilage using quantitative MR as well as for semiquantitative scoring of cartilage disease. The chapter explains the relevance of MR in identifying disease status, in monitoring disease progression, and in identifying risk factors of osteoarthritis, as well as in evaluating treatment response to so-called structure-modifying osteoarthritis drugs. The practical methodological procedures presented involve the description of how to acquire MR images for structural analysis and the semiquantitative scoring of articular cartilage. We also present a description of image-analysis techniques for cartilage segmentation and characterization of cartilage structure (quantitative outcome parameters, such as volume and thickness) and guidelines for how to test the validity (accuracy), precision (reproducibility), and sensitivity to change of such methodologies in osteoarthritis.