Abstract

The position sense of the knee joint was investigated in normal subjects lying in the supine position with both legs hanging freely. Three different manoeuvres were used to bring one leg into an extended position: voluntary activation of the quadriceps muscle, reflex activation of the quadriceps (TVR) and passive lifting of the leg. For each manoeuvre the subjects indicated with the other limb their perception of the joint position. It was found that the position produced by voluntary contraction was correctly perceived, that of the TVR was underestimated, and that of passive lifting was overestimated. The findings indicate that receptors in limb muscles may be used to judge limb position in addition to joint receptors and sense of effort. The findings are supported by repeated observations that muscle vibration can cause movement-illusions during isometric conditions.