MR imaging rapidly is emerging as a tool of unparalleled power for examining the articular cartilage and other important structures in diarthrodial joints. In addition to delineating the morphology of cartilage, MR imaging is capable of quantifying a variety of compositional and functional parameters relevant to arthritis. Moreover, because MR imaging is a nondestructive technique, multiple parameters can be analyzed in the same region of tissue and frequent serial examinations can be performed on even asymptomatic patients. This offers an unprecedented opportunity to study arthritis in ways not imaginable before and potentially to expand the envelope of MR imaging to include a population of patients for whom imaging has had relatively little to offer.