The role of joint innervation in the pathogenesis of arthritis

Recently, an expanding body of knowledge has documented the nature and func tions of receptors in joint tissues and their potential importance in prese rving the smooth normal functioning of the motor-skeletal system and in amp lifying the inflammatory response to joint injuries and diseases. This revi ew summarizes the current knowledge of the anatomical and physiological sub strates of these: mechanisms. The distribution, morphologic and functional characteristics of joint receptors have been well described. In the past de cade there has been a new appreciation of the major role played by sensory neurons in promoting regional inflammatory responses, and many of the speci fic neuronal mechanisms and molecules that mediate these reflexes have been identified. This knowledge promises to significantly improve the selectivi ty and effectiveness of pharmacologic approaches to pain, trauma and region al inflammatory disorders. Other investigations have revealed important contributions of joint recepto rs to motor function. These refer not to proprioception or the sense of lim b position in space, but rather to a more sophisticated tailoring of muscle activity to increase joint stability and to protect joint structures from damaging loads. Whether a loss of these reflexes may play a role in the pat hogenesis of osteoarthritis remains controversial. However, there is a grow ing consensus that a loss of these reflexes map contribute to the morbidity associated with disruption of the anterior cruciate ligament. Synovial joints are sites of major interactions between the musculoskeletal and the nervous systems. Understanding the mechanisms that activate and co ntrol these interactions will certainly offer the opportunity to develop ne w, more effective treatments for patients with joint disorders.