Structural associations of osteoarthritis pain: lessons from magnetic resonance imaging

For many years the search for structural associations of osteoarthritis (OA) pain were based on conventional radiographic imaging that predominantly visualizes bone. As well as being tomographic, magnetic resonance imaging (MRI) has the ability to directly visualize all the structures of a joint, including soft tissue and cartilage. Initial MRI studies focused on cartilage assessment, but recently there has been a growing body of work examining the correlation of structural findings with pain in OA and their relation to structural progression. Painful OA knees have more MRI-detected abnormalities and these pathologies are often correlated making individual contributions difficult to assess. However, in large cohort studies, both synovial hypertrophy and large synovial effusions were demonstrated to be more frequent in patients with OA knee pain. Similarly MRI-determined subchondral bone marrow oedema lesions (BME), particularly large ones, are associated with OA knee pain. Meniscal tears in OA knees, although common, have not been linked with pain. Improved, reliable quantification of the structural features and the rapid advances in MRI technology can only improve structure-pain understanding.