Follow us on :

Take a look at the Recent articles

AC: Electrostatic lubrication of natural joints

Raghuvir Pai

Department of Mechanical and Manufacturing Engineering, Manipal University, Manipal, India

E-mail : aa

DOI: 10.15761/GMO.1000154

Article Info
Author Info
Figures & Data


This monograph attempts to explain a new joint lubrication mechanism with surface active phospholipids as a lubricant. It provides studies of the principles of cartilage (smart material) of biological micro- and nanotribology.

Key words

articular cartilage, natural lubrication, lamellar-repulsive mechanism of lubrication of natural joints

The monograph consists of 160 text pages, 9 chapters and contains 95 figures’ with about 300 bibliographic items in alphabetical order.  The monograph is based on the author's own research and is very interesting because the subject of research is the surface of the natural joints. The author has determined the biophysical and biochemical parameters of articular cartilage and suggests a new mechanism of lubrication in natural joints. The Lamellar-repulsive joint lubrication mechanism is not so well-known in tribology and therefore deserves to be published.

The chemical and physical nature of the biological surfaces is seen in an entirely different light than that of engineering surfaces immersed in water. This book attempts to explain a new joint lubrication mechanism with surface- active phospholipids (PLs) as a lubricant.  Joint lubrication is a complex problem and attributing macromolecules to the synovial fluid of the lubricant cannot fulfill all the functions. The self-organization process of a stable pore structure in phospholipid liposomes, bilayers, lamellar phases in the synovial fluid forces the lamellar-repulsive mechanism of lubrication.  The lubricant is chemically attached to the surface and is responsible for the biological lubrication mechanism.

In an animal’s body, where the tissues slide over each other, the lubrication mechanism has been referred to as a “lamellar-repulsive”, because the surfaces coated with PL bilayers and lamellar phases negatively charged on articular surface with synovial fluid support this mechanism.

By giving an overview of physicochemical properties, the cartilage surface parameters like wettability and surface energy were determined using atomic force microscopy (AFM) and confocal microscopy (CFM). Friction of amphoteric and negatively charged cartilage surfaces (-PO4-) is also determined. Professor Pawlak has provided a comprehensive text to the biomechanics of frictional surfaces. The study provides the basis for the principles of biological micro- and nanotribology.

The amphoteric PLs are the main solid-phase components on the surface of an Articular Cartilage (AC). The liposomes were used as the model membrane to characterize the interfacial energy over the pH range 1 to 9.5, the isoelectric point (at pH~ 4.20) and amphoteric character of phospholipid bilayers.  Cartilage phospholipidic membrane has been shown to undergo conformational reorientation when wettability changed from the wet (~ 0°) super hydrophilic to dry-air  (103°) hydrophobic state (named smart material).

It has been well established that low friction is supported by the PLs bilayers mechanism which essentially consists of a Surface Amorphous Layer (SAL) surrounded by a 0.155 M electrolyte Synovial Fluid (SF) of pH ~7.4 with high-molecular-weight charged biomacromolecules.  The cartilage implication from osteoarthritis disease by a gradual erosion of the surface amorphous layer has shown an increased friction coefficient.  The author in this book demonstrates experimentally that the cartilage smart biomaterial pH is sensitive to friction and introduces a novel concept in joint lubrication on charged surfaces.

The book is an excellent starting point for medical and biomechanical students and researchers working with biological systems. Also, it will be useful in areas of high technology and nano-material sciences.  The reviewer is of the opinion that the book presents the original experimental results which very important for the understanding of joint lubrication and deserves all the respect for reading [1] (Figure 1).

Figure 1. Cover page of the book


1.0 Introduction                                                                                   1

2.0 The structure, composition and function of cartilage           5

2.1 Synovial fluid                                                                           11

2.2 Phospholipid bilayers as a potential solid lubricant         17

2.3 Phospholipids                                                                          21

2.4 Cartilage and antiphospholipid antibody syndrome         25 

3.0 Surface cartilage characteristics                                       35

3.1 Interfacial energy of PL bilayers                                     39

3.2 Cartilage surface wettability vs. pH                                45

3.3 Friction vs. wettability of cartilage surface                      53

3.4 Amphoteric cartilage and its consequences                     64

3.5 Cartilage surface charge density vs. pH                           75

4.0 Porosity of lubricated cartilage surface                              85

5.0 The boundary and boundary-layered lubrication                89

6.0 Lamellar-repulsive mechanism of low friction in Nature     93

7.0 Resurfacing cartilage surface                                             107

8.0 Articular cartilage restoration and regeneration                  123

9.0 Summary and outlook                                                             131

About the Author                                                                           137

Bibliography                                                                                   139

Index                                                                                                 153


  1. Pawlak, Zenon (2018) Articular Cartilage: Lamellar-Repulsive Lubrication of Natural Joints, Kindle Direct Publishing, 171pp. Print-book:, e- book:

Editorial Information


Article Type

Opinion Article

Publication history

Received: December 19, 2018
Accepted: December 29, 2018
Published: December 31, 2018


©2018 Raghuvir Pai. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Pai R (2018) AC: Electrostatic lubrication of natural joints. 2: DOI: 10.15761/GMO.1000154

Corresponding author

Raghuvir Pai

Department of Mechanical Manipal University, Manipal,India

Figure 1. Cover page of the book