Imaging pain in arthritis: advances in structural and functional neuroimaging.

Arthritis is a heterogeneous disease characterized by joint stiffness, swelling, and pain. Although primarily considered a peripheral joint disease, the severity of pain reported by arthritis patients does not always reflect the extent of joint pathology detectable by conventional means. Using structural and functional brain imaging techniques, a growing number of evolving neuroimaging methods are providing insight into these observed discrepancies at different time-scales. Of these methods, functional magnetic resonance imaging is exploited for short-term evoked pain examination and treatment evaluation; 'resting-state' approaches provide insight into fluctuations in pain; perfusion imaging captures elements of on-going clinical pain; and morphological brain assessment provides evidence for long-term structural changes in the brain associated with chronic pain. Further insight into arthritic pain processing at the brain-systems level could in the future be provided by combined neuroimaging approaches, specifically investigating the interactions between functional and structural alterations.