An understanding of the anatomy is invaluable when such small structures as described here are to be evaluated. Because MR imaging reveals greater detail, radiologists are obliged to use the information available to benefit the clinician and the patient. A working knowledge of the anatomic elements and their nomenclature also engenders confidence in the imager on the part of the hand surgeon. This discussion serves as the basis for meaningful comprehension of the pathologic entities that are presented in the articles that follow.