Activity of Knee Joint Proprioceptors Recorded from the Posterior Articular Nerve †

In recent years it has become possible for the first time to support the term "joint sense" with scientific evidence which proves that such a mechanism actually does exist. In 1944 Gardner' presented a thorough investigation of the innervation of the knee joint in cats and described the various types of sensory endings which are found in the capsule. He concluded that the Ruffini type endings appear to be derived from the posterior and medial articular nerves which are branches of the tibial and femoral nerves respectively. Andrew and Dodt' recorded firing from the medial articular nerve in response to joint movement, and others""'7 have reported firing from the posterior articular nerve of the cat in response to knee joint movements. The chief difference between the activity of medial nerve proprioceptors' as compared with posterior nerve proprioceptors' was that the former seemed uniformly to be slow adapting type receptors which fired only during critical joint angles, while the latter appeared to fall into a fast adapting type, which fired only during point movement, and a slow adapting type, which usually fired at most angles measured. This difference may conceivably have been the result of the restrictions imposed by the experimental method of Boyd and Roberts,' since it is apparent that they could only move the joint through roughly one-third of its normal range. The purpose of the investigation described below was to determine the activity of posterior nerve proprioceptors during the full physiological range of flexion-extension movements.