MRI is clearly the imaging modality of choice for detecting and exploring joint, osseous, and soft tissue injuries in the lower extremity and throughout the musculoskeletal system. Its ability to detect and differentiate the various forms of marrow pathology is unrivaled, and as such it should be obtained early in the work-up of a patient with a suspected marrow abnormality. Additionally, the radiologist must be familiar with the MRI appearances of normal marrow and the most common types of marrow pathology if its diagnostic power is to be fully realized.