Innervation of the Tibial Epiphysis Through the Intercondylar Foramen

Bone. 2019 Mar;120:297-304. doi: 10.1016/j.bone.2018.11.007. Epub 2018 Nov 13.

Abstract

The periosteum and mineralized bone are innervated by nerves that sense pain. These include both myelinated and unmyelinated neurons with either free nerve endings or bearing nociceptors. Parasympathetic and sympathetic autonomic nerves also innervate bone. However, little is known about the route sensory nerves take leaving the epiphyses of long bones at the adult knee joint. Here, we used transgenic mice that express fluorescent Venus protein in Schwann cells (Sox10-Venus mice) to visualize myelinated and unmyelinated nerves in the tibial epiphysis. Immunofluorescence to detect a pan-neuronal marker and the sensory neuron markers calcitonin gene-related peptide (CGRP) and tropomyosin receptor kinase A (TrkA) also revealed Schwann cell-associated sensory neurons. Foramina in the intercondylar area of the tibia were conserved between rodents and primates. Venus-labeled fibers were detected within bone marrow of the proximal epiphysis, exited through foramina along with blood vessels in the intercondylar area of the tibia, and joined Venus-labeled fibers of the synovial membrane and meniscus. These data suggest that innervation of the subchondral plate and trabecular bone within the tibial epiphysis carries pain signals from the knee joint to the brain through intercondylar foramina.

Keywords: Epiphysis; Foramen; Knee joint; Schwann cells; Sensory neuron; Tibia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Vessels / metabolism
  • Epiphyses / diagnostic imaging
  • Epiphyses / innervation*
  • Mice, Transgenic
  • Platelet Endothelial Cell Adhesion Molecule-1 / metabolism
  • Rats, Sprague-Dawley
  • Receptor, trkA / metabolism
  • SOXE Transcription Factors / metabolism
  • Schwann Cells / metabolism
  • Tibia / diagnostic imaging
  • Tibia / innervation*
  • Tomography, X-Ray Computed

Substances

  • Platelet Endothelial Cell Adhesion Molecule-1
  • SOXE Transcription Factors
  • Receptor, trkA