An autoradiographic study of the distribution of sensory nerve endings in the knee joint of the rat.

The distribution of sensory nerve endings of the knee joint in rats has been investigated by autoradiography of 3H-leucine. Sections were made and each section was examined by autoradiography and silver impregnation staining. Free nerve endings were found only in the synovial membrane, the menisci and their synovial junction. In the joint capsule, capsulated sensory nerve endings were sparsely distributed. Numerous sensory nerve endings were found at the insertion of the patellar ligament, the collateral ligament and the cruciate ligament. These resembling Golgi-Mazzoni nerve endings or capsulated sensory nerve endings are thought to be proprioceptors. Radioactivity, which would indicate the presence of sensory nerve endings, was not recognized in the osseous tissue. It is hypothesized that proprioceptor at the insertion of ligaments plays an important role as monitor of joint motion by the reflex pathway.