Spinal pain, especially low back pain (LBP), is a widespread clinical and diagnostic problem for both patients and physicians, because back pain has an equivalently wide variety of causes and provocations. Because of its variable nature and manifestations, back pain is challenging to diagnose and treat correctly. In addition, the pain is induced not only by direct mechanical pressure such as a herniated disk or degenerated bone but also by inflammation and associated proinflammatory cytokines. To help guide further diagnostic workup or the next step in management, radiologists should be familiar with the causes, mechanisms, and diagnostic clues provided by MRI. The authors review the microscopic and macroscopic mechanisms for each category of LBP and depict the relationship between imaging findings and pain mechanisms. This review focuses on the detailed anatomy related to the pain-signaling pathway and the roles of chemicals in inducing different mechanisms of LBP. MRI findings that serve as representative examples of key concepts are demonstrated according to each mechanism, and treatment options are reviewed on the basis of different causes of LBP. By knowing these concepts, radiologists can help correlate imaging findings with potential underlying mechanisms and help guide clinicians in the management of LBP. ©RSNA, 2020.