The histology of the anterior cruciate ligament was studied by a
modified technique of the Gairns gold chloride stain for neural elements.
Three morphological types of mechanoreceptors and free nerve-endings were
identified: two of the slow-adapting Ruffini type and the third, a rapidly
adapting Pacinian corpuscle. Rapidly adapting receptors signal motion and
slow-adapting receptors subserve speed and acceleration. Free
nerve-endings, which are responsible for pain, were also identified within
the ligament. These neural elements comprise 1 per cent of the area of the
anterior cruciate ligament.