Modic changes (MCs) are bone marrow changes in the spine, and they are classified into three categories (types 1, 2, and 3) based on magnetic resonance imaging (MRI) appearance. They share several determinants with bone marrow changes at other sites of the body. The precise pathology of MCs is still unclear but includes structural disc damage and the inflammatory response to it, atypical mechanical loading, and possible bacterial etiology. In particular, Modic type 1 change (MC1) is thought to be associated with low back pain (LBP) but may also occur among the normal, asymptomatic population. However, MC1 may play a role, especially among patients with chronic, troublesome LBP. Clinically, MCs are diagnosed using MRI with no evident clinical tests or diagnostic algorithms. Unfortunately, no evidence-based treatment options exist yet for patients with pain and MCs although fusion surgery, antibiotic, and nerve ablation treatment are being explored. Overall, MCs are clinically important structural spine phenotypes, with varied etiology and prognostics and a need for refined classification.