REDUCTION OF SENSORY RESPONSES TO PASSIVE MOVEMENTS OF INFLAMED KNEE JOINTS BY HYLAN, A HYALURONAN DERIVATIVE

Hyaluronan (sodium hyaluronate) is a glycosaminoglycan that is present in all joint tissues. Painful arthritic joints have been characterize d by hyaluronan of reduced elastoviscosity. The purpose of this invest igation was to determine whether hyaluronan has an influence on joint nociceptor sensitivity and whether restoration of elastoviscosity woul d decrease nerve responses from nociceptive afferent fibers in arthrit ic joints. Nerve impulse activity was recorded from nociceptive affere nt fibers of the medial articular nerve in anesthetized cats. An acute experimental arthritis was produced by intra-articular injection of k aolin and carrageenan. This caused, within 3 h, the development of ong oing nerve activity and enhancement of nerve impulse responses to pass ive movements in the normal range of the joint. Intra-articular inject ion of an elastoviscous solution of hylan, a hyaluronan derivative, si gnificantly reduced both the ongoing activity and the movement-evoked responses in 1-2 h. This effect was not obtained when a nonelastovisco us solution of hylan was injected into the inflamed joint. The results indicate that intra-articularly injected elastoviscous solutions of h ylan reduced nociceptive activity in inflamed joints through an elasto viscous, rheological effect on nociceptive afferent fibers through the intercellular matrix in which these fibers are embedded.