Changes in blood pressure and heart rate induced by movements of normal and inflamed knee joints.

The effects of passive movements of normal and inflamed knee joints on blood pressure and heart rate were recorded in baroreceptor denervated cats anesthetized with halothane, and these effects were compared with those obtained by severe noxious squeezing of the hind paw. Rhythmic flexions and extensions as well as rhythmic inward and outward rotations of a normal knee joint in its physiological working range did not have any significant influence on blood pressure and heart rate. However, on the inflamed side, the same movements caused definite increases in blood pressure and heart rate (e.g. mean increases for flexion-extension movements were 13 mmHg and 4 beats/min, respectively, P less than 0.01). Static outward rotations in the normal working range were ineffective in both joints, but as soon as these static rotations were extended into the noxious range significant increases in blood pressure and heart rate were elicited. The respective mean increases induced from the normal and inflamed sides were 17 and 38 mmHg for the blood pressure and 4 and 8 beats/min for the heart rate. The increases in blood pressure and heart rate induced by noxious outward rotation of the inflamed joint regularly exceeded those elicited by noxious squeezing of the hind paw. It is concluded that impulses in articular nociceptors and possibly other fine articular afferent units activate sympathetic outflow to the cardiovascular system, and that these effects are particularly prominent when the joint receptors are sensitized by