Structural correlates of pain in osteoarthritis.

Osteoarthritis (OA) is the most common form of arthritis, with knee OA itself being among the most common conditions and a leading cause of disability among older adults worldwide. Pain is a key symptom in the decision to seek medical attention, yet available therapies for managing OA are limited with only minimal or moderate efficacy. Current approaches to pain management in OA have been rather non-specific, limited to acetaminophen or NSAIDs primarily, without targeting underlying structural lesions that may be contributing to pain in OA. With the advent of MRI, a number of studies have noted the importance of bone marrow lesions and synovitis/effusion to the pain experience in OA. These pathologic features are therefore attractive treatment targets, with some proof-of-concept studies demonstrating the potential efficacy of targeting these lesions. Another increasingly recognised important contribution to pain in OA is sensitisation, which is associated with pain severity. Synovitis/effusion have been identified as potentially leading to development and worsening of sensitisation. Much work remains to be done in understanding the mechanisms by which structural pathology causes pain; such insights are urgently needed to develop new treatment approaches to help millions of people worldwide who are burdened by pain from OA.