Pathogenesis and management of pain in osteoarthritis.

The term osteoarthritis describes a common, age-related, heterogeneous group of disorders characterised pathologically by focal areas of loss of articular cartilage in synovial joints, associated with varying degrees of osteophyte formation, subchondral bone change, and synovitis. Joint damage is caused by a mixture of systemic factors that predispose to the disease, and local mechanical factors that dictate its distribution and severity. Various genetic abnormalities have been described, but most sporadic osteoarthritis probably depends on minor contributions from several genetic loci. Osteoarthritic joint damage may be associated with clinical problems, but the severity of joint disease is only weakly related to that of the clinical problem. For this reason the associations and pathogenesis of pain are in as much need of investigation as joint damage. Subchondral bone and synovium may be responsible for nociceptive stimuli, and peripheral neuronal sensitisation is an important feature, and can result in normal activities (such as walking) causing pain. Central pain sensitisation can also occur, and psychosocial factors are important determinants of pain severity. We present a stepwise approach to the management of osteoarthritis.