The response of slowly adapting mechanoreceptors in the cat knee joint to tetanic contraction of hind limb muscles.

The effect of tetanic contraction of muscles acting at the cat knee joint on the discharge of various types of slowly adapting knee joint receptors was investigated. Contraction of a particular muscle could either increase, decrease or produce no alteration in the discharge of a given receptor. Whatever effects were produced by muscle contraction, these effects were always maximal at extremes of the flexion/extension range, and enhanced by limb movement. However, these receptors could not be induced to discharge at intermediate positions either by the passive tension or active contraction of muscles around the knee joint. It is concluded that muscle contraction does not increase the proportion of joint receptors (approximately 18%) which are known to spontaneously discharge at intermediate positions in the absence of significant muscle tone (Ferrell, 1980).