The ultrastructure of sensory nerve endings in human anterior cruciate ligament

The sensory innervation of the anterior cruciate ligament (ligamentum cruciatum anterius) of the human knee joint was studied by light- and electron microscopy. The connective tissue between the synovial membrane and the cruciate ligament contains small Ruffini corpuscles and lamellar corpuscles with several inner cores. The connective tissue septa between the individual fascicles of the cruciate ligament contain Ruffini corpuscles and free nerve endings. The free nerve endings are innervated by C-fibres and myelinated A-delta fibres. The afferent axons of Ruffini corpuscles are myelinated and measure 4-6 microns in diameter, those of the lamellar corpuscles with several inner cores measure about 6 microns in diameter. It is discussed, whether these receptors of the anterior cruciate ligament may influence the muscle tone via polysynaptic reflexes.