MRI is a tool of unprecedented capabilities for evaluating arthritis and its progression. Not only can it non-invasively delineate the anatomy of all components of a joint with unparalleled clarity, MRI is also capable of probing important functional and compositional parameters of disease in these tissues. Particularly intriguing is MRI's potential for identifying very early changes of joint disease when clinical symptoms may be minimal or absent. Early detection of patients who are at risk for developing progressive disease may allow appropriate treatment to be initiated earlier, when there may be a greater chance of favourable outcome. MRI can, furthermore, provide objective and quantitative measures of disease progression and treatment response. Certain parameters, such as articular cartilage volume, have been validated cross-sectionally; however, their longitudinal performance has yet to be established. Further work is, therefore, necessary to thoroughly validate and optimize some of these measures so that they can begin to be used in more powerful ways to explore the pathophysiology and potential therapies of arthritic disorders.