MRI is more sensitive than radiography for detecting spinal changes, especially corresponding to the thoracic spine, which is partially obscured by lung tissue and ribs at radiography.

MRI can show signs of disease activity (inflammation) in the form of fluid accumulation (oedema) and increased blood flow (contrast enhancement) in the bone marrow and/or joints. In early stages there is often inflammation corresponding to vertebral corners. They occur before the appearance of chronic changes which manifest as contour changes at vertebral corners and new bone formation.

MRI can also show chronic changes in the form of fatty accumulation in bone marrow, usually corresponding to vertebral corners, erosion, new bone formation, fusion of vertebrae etc.