Mechanoreceptors in human cruciate ligaments. A histological study

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.