1. A method of assessing cartilage damage or disease in a joint comprising cartilage and accompanying bone on either side of the joint, which method comprises (a) obtaining a three-dimensional map of cartilage of said joint in which said map demonstrates thickness or biochemical contents or relaxation time of both normal and damaged or diseased cartilage of said joint, and (b) determining at least one margin between damaged or diseased cartilage and normal cartilage in said three-dimensional map.