Distribution of neurofilament-positive nerve fibres and sensory endings in the human anterior cruciate ligament.

The present immunocytochemical study describes the distribution of neurofilament-containing nerve fibres and corpuscular-like endings in the human anterior cruciate ligament. The entire anterior cruciate ligament of a non-injured knee joint from a child was cut into serial 15-microns-thick frozen sections, which were processed for immunofluorescence staining with a monoclonal antibody against the 68-kDa neurofilament subunit. Numerous neurofilament-positive fibres were found in bundles. These bundles were mostly located near blood vessels in the subsynovial layer and in interfascicular gaps. Only a few single nerve fibres were found independent of blood vessels in interfascicular gaps and between collagen bundles. Neurofilament-containing nerve fibres were preferentially located near the bony attachments of the anterior cruciate ligament. Two types of corpuscular-like endings were found, i.e. "spiral-like" (type I) and "spray-like" (type II) endings. Similarly to nerve fibres, both types of corpuscular-like endings were found mainly near the tibial and femoral attachment sites (15 of 17), whereas only two were found in the middle third of the ligament. Most likely, the type I and type II corpuscular-like endings serve a mechanoreceptive function involved in the sensory control of normal movements and in stress protection.