Quantitative relaxometry extends MRI beyond anatomical imaging and provides information on the physical structure, composition, and functional state of cartilage. Quantitative MRI techniques reflect the interaction of water with cartilage macromolecules and allow detection of early biological changes in cartilage. This part of the educational course is an overview of the most established techniques for quantitative relaxometry of cartilage, namely T2, T2* and T1ρ mapping and dGEMRIC. We will review their relationship with physiological properties of cartilage and give a description of their potential value as diagnostic biomarkers followed by a discussion of the limitations and challenges towards clinical applications.