Innervation of lumbar zygapophyseal joint synovial folds

In a study of lower lumbar zygapophyseal facet joints, nerves have been demonstrated in the synovial folds by means of a silver impregnation method. The diameter of the nerves ranged from 0.6 to 12 microns; the number of fibers per nerve ranged from 1 to 5. They generally run a course separate from blood vessels, indicating that they are afferent nerves which probably have a nociceptive function. This finding may be relevant to low back pain.