Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. May 18, 2017; 8(5): 372-378
Published online May 18, 2017. doi: 10.5312/wjo.v8.i5.372
Light and electron microscopic study of the medial collateral ligament epiligament tissue in human knees
Georgi P Georgiev, Alexandar Iliev, Georgi Kotov, Plamen Kinov, Svetoslav Slavchev, Boycho Landzhov
Georgi P Georgiev, Plamen Kinov, Department of Orthopaedics and Traumatology, University Hospital Queen Giovanna-ISUL, Medical University of Sofia, BG 1527 Sofia, Bulgaria
Alexandar Iliev, Georgi Kotov, Boycho Landzhov, Department of Anatomy, Histology and Embryology, Medical University of Sofia, BG 1431 Sofia, Bulgaria
Svetoslav Slavchev, University Hospital of Orthopaedics “Prof. B. Boychev”, Medical University of Sofia, BG 1614 Sofia, Bulgaria
Author contributions: Georgiev GP and Landzhov B performed the ultrastructural study and analysed the data from transmission electron microscopy and light microscopy; Iliev A, Kinov P and Slavchev S performed the histologic investigations; Kinov P, Slavchev S and Landzhov B helped in preparing the manuscript; Georgiev GP designed and coordinated the research; Georgiev GP, Iliev A and Kotov G wrote the paper; all authors approved the final version of the article to be published.
Institutional review board statement: The study was approved by the Medical University of Sofia Institutional Review Board.
Institutional animal care and use committee statement: No animals were analysed during this study.
Conflict-of-interest statement: The authors declare that there is no conflict of interest regarding the publication of this article.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Georgi P Georgiev, MD, PhD, Department of Orthopaedics and Traumatology, University Hospital Queen Giovanna-ISUL, Medical University of Sofia, 8 Bialo More St., BG 1527 Sofia, Bulgaria.
Telephone: +359-88-4493523
Received: December 21, 2016
Peer-review started: December 25, 2016
First decision: February 17, 2017
Revised: February 23, 2017
Accepted: March 12, 2017
Article in press: March 13, 2017
Published online: May 18, 2017

To examine the normal morphology of the epiligament tissue of the knee medial collateral ligament (MCL) in humans.


Several samples of the mid-substance of the MCL of the knee joint from 7 fresh human cadavers (3 females and 4 males) were taken. Examination of the epiligament tissue was conducted by light microscopy and photomicrography on semi-thin sections of formalin fixed paraffin-embedded blocks that were routinely stained with haematoxylin and eosin, Mallory stain and Van Gieson’s stain. Electron microscopy of the epiligament tissue was performed on ultra-thin sections incubated in 1% osmium tetroxide and contrasted with 2.5% uranyl acetate, lead nitrate, and sodium citrate.


The current light microscopic study demonstrated that the epiligament of the MCL consisted of fibroblasts, fibrocytes, adipocytes, neuro-vascular bundles and numerous multidirectional collagen fibers. In contrast, the ligament body was poorly vascularised, composed of hypo-cellular fascicles which were formed of longitudinal groups of collagen fibers. Moreover, most of the vessels of the epiligament-ligament complex were situated in the epiligament tissue. The electron microscopic study revealed fibroblasts with various shapes in the epiligament substance. All of them had the ultrastructural characteristics of active cells with large nuclei, well developed rough endoplasmic reticulum, multiple ribosomes, poorly developed Golgi apparatus, elliptical mitochondria and oval lysosomes. The electron microscopy also confirmed the presence of adipocytes, mast cells, myelinated and unmyelinated nerve fibers and chaotically oriented collagen fibers.


Significant differences exist between the normal structure of the ligament and the epiligament whose morphology and function is to be studied further.

Keywords: Knee, Epiligament, Knee medial collateral ligament, Electron Microscopy, Humans, Microscopy, Photomicrography

Core tip: The epiligament of the medial collateral ligament of the human knee is an important enveloping supporting structure of the ligament proper containing fibroblasts, fibrocytes, adipocytes, mast cells, and neurovascural bundles in a network of collagen fibres that is not limited to the surface of the ligament but also pervades it, as the endoligament, thus providing the cellular elements and blood vessels that participate in the ligament’s nutrition and during the process of healing.