An anatomical study of the origin of sympathetic and sensory innervation of the elbow and knee joint in the monkey.

The origin of sympathetic and sensory innervation of the elbow and knee joint was studied by the intra-axonal transport method. After injection of WGA-HRP into the elbow and knee joint unilaterally in adult monkeys (macaca fascicularis), labelled cells were observed ipsilaterally in both the sympathetic and dorsal root ganglia. Following injection in the elbow joint the neurons were concentrated in the stellate and third to fourth thoracic (T3-T4) sympathetic ganglia, and in the fourth cervical to second thoracic spinal sensory ganglia. The knee joint injection resulted in labelling of sympathetic and spinal sensory ganglia, preferentially at the lumbo-sacral junction--the third lumbar to third sacral (L3-S3) ganglia. The functional implications are discussed in relation to pain mechanisms of joints and to an earlier hypothesis that the nervous system might be involved in the pathogenesis of chronic joint inflammation.