We obtained human cruciate ligaments at the time of total knee
replacement and from autopsy and amputation specimens, and examined
histological sections of the ligaments for the presence of mechanoreceptors
using the Bodian, Bielschowsky, and Ranvier gold-chloride stains for axons
and nerve-endings. The cruciate ligaments obtained at the time of total
knee replacement were too distorted by disease processes to be of use. The
autopsy and amputation specimens, however, contained fusiform
mechanoreceptor structures measuring 200 by seventy-five micrometers, with
a single axon exiting from the capsule of the receptor. One to three
receptors were found at the surface of each ligament beneath the synovial
membrane, and were absent from the joint capsules and menisci.
Morphologically the receptors resembled Golgi tendon organs, and it seems
likely that they provide proprioceptive information and contribute to
reflexes inhibiting injurious movements of the knee. This is the first
histological demonstration of mechanoreceptors in human cruciate
ligaments.