I

SUPERVISOR DECLARATION

“I hereby declare that I have read this thesis and in my opinion this report is

sufficient in terms of scope and quality for the award of the degree of Bachelor of

Mechanical Engineering (Structure & Materials)”

Signature : …………………………

Supervisor : DR MOHD JUZAILA BIN ABDUL LATIF

Date : …………………………

II

BIOMECHANICAL CHARACTERISATION OF ARTICULAR CARTILAGE

ACROSS SYNOVIAL JOINT

LIEW GUO REN

This report was submitted in fulfillment of the requirement for the award of

Bachelor of Degree of Mechanical Engineering with Honours (Structure &

Materials)

Faculty of Mechanical Engineering

Universiti Teknikal Malaysia Melaka

JUNE 2015

III

DECLARATION

“I hereby declare that the work in this report was my own except for summaries and

quotations which have been duly acknowledged.”

Signature : …………………………

Author : LIEW GUO REN

Date : …………………………

IV

ACKNOWLEDGEMENT

I am using this opportunity to express my gratitude to everyone who supported

me throughout my Final Year Project. I am thankful for their aspiring guidance,

invaluably constructive criticism and friendly advice during the project work. I am

sincerely grateful to them for sharing their truthful and illuminating views on a number

of issues related to the project.

Among others, I would like to express my warm thanks to my final year project

supervisor, Dr. Mohd Juzaila Bin Abdul Latif, whose contribution in stimulating

suggestion and encouragement, helped me to coordinate my project especially in

writing this report. I am indebted to him for all the knowledge, wisdom and experience

he shared during my studies.

Furthermore, I would like to express my appreciation to the master students:

Yusra and Hikmah; Research fellow: Kevin, Mean Yee, Firdaus and Hajar, who have

always sharing their knowledge and idea with me.

A person is guided along his way by many people and it is impossible to name

all of them. I take this opportunity to thank all of them especially to my family and

friends for their encouragement and understanding during I was working on my thesis.

V

ABSTRAK

Osteoarthritis (OA) ialah sejenis penyakit degeneratif articular cartilage yang

biasa dijangkiti oleh kumpulan umur sederhana dan kumpulan warga emas. Penyakit

ini adalah satu keadaan jangka panjang yang boleh merosot kualiti hidup seseorang.

Punca OA masih belum difahami secara penuh. Cartilage biasa dikenali sebagai bahan

galas yang cemerlang sebab ia memperolehi permukaan yang licin untuk articulation

dan memudahkan penghantaran beban dengan geseran yang rendah. Dalam kajian

eksperimen yang sebelumnya, kebanyakan penyelidik menggunakan specimen

cartilage yang kecil untuk mewakili seluruh bahagian cartilage untuk menjalankan

eksperimen. Fokus utama kajian ini adalah untuk menyiasat sifat biomekanikal

articular cartilage di seluruh sinovia lembu. Cartilage sendi sinovia lembu telah

digunakan untuk kajian ini kerana ianya lebih mudah didapatkan berbanding dengan

cartilage manusia. Dengan menggunakan ujian kasturi jalar, menjalankan ujian in situ

di tempat yang berlainan atas articular cartilage. Method kumputer juga digunakan

dalam kajian ini untuk menyiasat sifat biomekanikal articular cartilage di seluruh

sinovia. Sifat-sifat biomekanikal kesuluruhan articular cartilage di seluruh sendi

sinovia akan diuji dalam kajian ini. Ketebalan cartilage yang didapati dari kajian ini

adalah dalam julat yang sama jika berbanding dengan kajian yang sebelumnya. FE

model telah dimodelkan mengikut ketebalan cartilage yang diukur dari ujian

indentation untuk mensimulasikan pore pressure dan contact pressure articular

cartilage. Daripada kajian ini, ketebalan akan mempengaruhi sifat biomekanikal

articular cartilage. Pore pressure dan contact pressure meningkat sekiranya ketebalan

articular cartilage meningkat.

VI

ABSTRACT

Osteoarthritis (OA) is a degenerative disease of articular cartilage, which is

normally affected by middle aged and senior citizen group. This disease is a common

long term condition which can result in an ongoing loss of quality of life. The cause of

OA is still not yet fully understood. The normal cartilage is known to be an excellent

bearing material that provides a smooth, lubricated surface for articulation and to

facilitate the transmission of loads with a low frictional coefficient. In previous

experimental studies, most of the researchers used the small specimen of cartilage in

order to represent the whole cartilage to conduct the experiment. The main focus of

this study is to investigate the biomechanical behavior of articular cartilage across

bovine synovial joint. The bovine’s synovial joint cartilages were used for this study

because it is easier to get compared to the human cartilage. By using the indentation

tests, performed in situ in order to measure cartilage thickness on the difference

location of the articular cartilage. The computational method is also used for this study

to investigate the biomechanical behavior of articular cartilage across the synovial

joint. The thickness found in the present study are within the similar range when

compared to the previous study. The FE model was modeled according to the cartilage

thickness measured from indentation test in order to simulate pore pressure and contact

pressure of the cartilage. From this study, it is concluded that thickness affects the

biomechanical behavior of articular cartilage. The pore pressure and contact pressure

increases as the thickness of the articular cartilage increased.

VII

TABLE OF CONTENT

CHAPTER CONTENT PAGE

SUPERVISOR DECLARATION I

DECLARATION III

ACKNOWLEDGEMENT IV

ABSTRAK V

ABSTRACT VI

TABLE OF CONTENT VII

LIST OF FIGURES X

LIST OF TABLES XII

LIST OF SYMBOLS XIII

LIST OF ABBREVIATION XIV

CHAPTER 1 INTRODUCTION 1

1.1 Introduction 1

1.2 Problem Statement 3

1.3 Objective 4

1.4 Scope 4

CHAPTER 2 LITERATURE REVIEW 5

2.1 Osteoarthritis 5

2.1.1 Causes 6

2.1.2 Diagnosis 8

2.1.3 Treatment 9

2.1.3.1 Non-pharmacologic 10

2.1.3.2 Pharmacologic 10

2.1.3.3 Intra-articular injection 11

2.1.3.4 Surgical 11

2.2 Synovial joint-anatomy and physiology 12

2.3 Articular cartilage 14

VIII

CHAPTER CONTENT PAGE

2.3.1 Structure and composition 15

2.3.1.1 Collagen 17

2.3.1.2 Proteoglycans 17

2.3.1.3 Water 18

2.4 Characterization of biomechanical properties

of articular cartilage 19

2.4.1 Material theory 19

2.4.2 Specimen preparation 20

2.4.3 Experimental testing 20

2.4.4 Thickness 24

2.4.5 Computational methods 26

2.5 Summary 28

CHAPTER 3 METHODOLOGY 30

3.1 Introduction 30

3.2 Material and specimen preparation 31

3.2.1 Phosphate Buffered Saline 31

3.2.2 Bovine articular cartilage 31

3.3 Indentation test apparatus 32

3.4 Calibration test 34

3.4.1 Calibration procedure 34

3.5 Creep indentation test 35

3.6 Cartilage thickness measurement 36

3.7 Computational methods 37

3.7.1 Implementation of contact dependent

flow 37

3.7.2 Model development: Repeat of previous

study 38

3.7.3 Model development: Simulation of

Experimental indentation test 39

IX

CHAPTER CONTENT PAGE

CHAPTER 4 RESULT AND DISCUSSION 42

4.1 Introduction 42

4.2 Cartilage Thickness 42

4.3 Computational results for idealized

Axisymmetric model 43

4.3.1 Implementation of contact dependent

flow 43

4.4 Biomechanical behavior of articular cartilage

Across synovial joint 44

4.4.1 Contact pressure 44

4.4.2 Pore pressure 46

4.5 Discussion 47

CHAPTER 5 CONCLUSION 52

5.1 Conclusion 52

5.2 Recommendation 53

REFERENCES 55

X

LIST OF FIGURES

FIGURE TITLE PAGE

1.1 Estimated patients in UK who have sought treatment for

osteoarthritis 2

2.1 The schematic diagram of OA affects a joint 7

2.2 Examples of image of knee joint by X-ray 8

2.3 Examples of image of knee joint by MRI 9

2.4 Structure of synovial joint in the knee 13

2.5 Schematic presentation of a knee joint 14

2.6 Schematic diagram of articular cartilage 15

2.7 Schematic diagram indicating the extracellular matrix of

articular cartilage 18

2.8 Schematic diagram of Confined compression test 22

2.9 Schematic diagram of unconfined compression test 23

2.10 The schematic diagram indentation test 24

2.11 Indentation test to determine cartilage thickness 25

2.12 Cartilage model developed by using ANSYS 28

3.1 Specimen preparation 32

3.2 Schematic diagram of the indentation test rig 33

3.3 Indentation test apparatus 33

3.4 Graph of calibration 34

3.5 Close view on the indentation specimen 35

3.6 Indentation test to determine cartilage thickness 36

3.7 Direction of fluid velocity vector 37

XI

FIGURE TITLE PAGE

3.8 Pawaskar’s model used for validate the implementation of

contact dependent flow detection algorithm.

(Pawaskar,2006) 38

3.9 Axisymmetric FE model of cartilage specimen 40

4.1 Comparison graph of Contact pressure distribution at

cartilage surface between current study with Pawaskar’s

result 44

4.2 Compress pressure distribution on articular cartilage

surface 45

4.3 Contact pressure distribution at cartilage surface for three

difference thickness 45

4.4 Compress pressure distribution on articular cartilage

surface 46

4.5 Pore pressure distribution on cartilage surface 47

4.6 Location point of specimen 48

4.7 Direction of cartilage deformation after loading 50

4.8 Direction of fluid flow for step load , 2 s 50

4.9 Direction of fluid flow after constant load, 1000 s 50

4.10 Direction of fluid flow of constant load during 0 mm radial

distance 51

XII

LIST OF TABLES

TABLE TITLE PAGE

2.1 Linear biphasic biomechanical properties of articular

cartilage in human synovial joints.

21

2.2 Cartilage properties of the Mature tibial plateau

determined from indentation test

26

3.1 Formulation of PBS tablet 31

3.2 Cartilage material properties used for FE validation model 39

4.1 Cartilage thickness for 3 difference points of articular

cartilage across synovial joint

43

XIII

LIST OF SYMBOLS

E – Young’s Modulus

H – Aggregate modulus

k – Permeability

mm – millimeter

Pa - Pascal

s – Second (time)

v – Poisson’s ratio

V – Voltage

ΔP – Pressure gradient

XIV

LIST OF ABBREVIATION

ECM- Extracellular matric

GAG- Glycosaminoglycans

LVDT – Linear variable differential transformer

MRI – Magnetic resonance imaging

NSAID – Nonsteroidal anti-inflammatory drugs

OA- Osteoarthritis

PBS - Phosphate buffered saline

PGs- Proteoglycans

STZ- Superficial Tangential Zone

1

CHAPTER 1

INTRODUCTION

1.1 Introduction

Osteoarthritis (OA) is the most prevalent of rheumatic diseases and is the

leading cause of pain and disability in most countries worldwide (Evangelos et al,

2001). This disease is a common long term condition which can result in an

ongoing loss of quality of life. The degradation and loss of articular cartilage in

synovial joint has been recognized as the main source of OA. Most of the OA

disability burden is attributable to the hips and knees. Research from Arthritis

Research UK Primary Care Centre shows that around 8.75 million people have

sought treatment for OA in two or more sites of the body in year 2013 as shown in

the Figure 1.1 (Arthritis Research UK, 2013). The prevalence of OA increases with

age and generally affects women more frequently than men, with the total number

of women exceeding 5 million, compared to 3.5 million men as shown in Figure

1.2 (Arthritis Research UK, 2013).

2

Figure 1.1: The estimated patients in UK who have sought treatment for

osteoarthritis, by gender and age group. a) By number of people, b) By

proportion of people. Adapt from Arthritis Research UK, 2013.

There are various joints in human body that may be affected by OA. However,

this disease is most likely to affects the hands, hips, knees, lower back and neck

(Nordqvist, 2014). Knee has one of the most complex and largest joint in the body

which is known as synovial joint. With the unique structure, synovial joints allow

very complex movements between adjacent bones like allow the leg to bend,

straighten and carries the body weight. The ends of the bone are covered by the

articular cartilage which are lubricated by the synovial fluid. The articular cartilage

act as a protective surface that cushions the ends of bone in the joints and allows

the joint to move smoothly.

There are two main causes of the OA, which are traumatic mechanical

destruction and progressive mechanical degeneration (tear and wear). The

traumatic mechanical destruction is due to the abnormal use and injury of the joint

while the progressive mechanical degeneration is due to aging. During OA, the

smooth surface of the cartilage will becomes rough and causing irritation. If the

cartilage wears down completely, thus exposing the underlying subchondral bone

and the bone in the joint may be rubbing against another bone, causing damage

and pain. There is no cure for OA as yet, but the pain normally relieved by either

a. b.

3

therapeutic or operational methods. The degradation of cartilage manifests itself in

the variations of its mechanical and biological properties (Carter et al., 2004). This

in turn causes the cartilage susceptible to structural failures, which degrades it

further.

There are plenty of researchers from multiple fields such as medicine,

engineering, chemistry, material science, etc have been studying the articular

cartilage at nano-, micro- and macro- levels. Most of these studies are centred

around to investigate about the biomechanical properties of the cartilage. A lot of

experiment had been carried out to characterize the biomechanical properties and

to study the behavior of the cartilage under different experimental and

physiological conditions (Mow et al., 1989; Kwan et al., 1990). Similarly,

computational models have been postulated to give firm theoretical foundations to

the understanding of the mechanical behavior of the cartilage (Mow et al., 1980;

Lai et al, 1991). However, the lack of mechanical property information on the

synovial joint cartilage posed a problem for computation modeling. Previous

studies have used the data get by the small specimen but it is not known either the

mechanical behavior of the specimen can represent the whole cartilage in a joint.

Therefore, the aim of this study was to develop a method to characterize the

thickness and biomechanical behavior of the articular cartilage across the synovial

joint using indentation test. This is to identify that the biomechanical properties of

the small specimen either can represent the whole joint.

1.2 Problem statement

The behaviour of the cartilage across the synovial joint is yet to be understood

because only certain locations of the cartilage were previously characterise to obtain

the biomechanical properties. Furthermore, most of the previous study of articular

cartilage using small specimen to represent the whole cartilage in a joint. These

assumptions were inappropriate and may limit the accuracy of the result since the

thickness of cartilage is different across the joint.

4

1.3 Objective

The objective of this study is to study the biomechanical behavior of articular cartilage

across the synovial joint.

1.4 Scope

The methods used for this project are the computational modeling method and the

experimental method (indentation test). The scope includes:

1 To determine the thickness of cartilage across synovial joint.

2 To establish the method to study biomechanical behaviors of cartilage across

synovial joint.

3 To study the biomechanical behaviors of cartilage across synovial joint.

5

CHAPTER 2

LITERATURE REVIEW

2.1 Osteoarthritis

Osteoarthritis (OA) are the most common type of arthritis especially for those

who reach middle age in United Kingdom. According to the National Health Service,

UK, approximately 8.5 million people are affected by this disease. The Arthritis

Foundation, USA, said that about 27 million Americans are affected in the year 2013.

The women are more likely to be affected by osteoarthritis than men after the age of

50. This symptoms typically start after 40 years of age, and progress slowly (Arthritis

Research UK, 2013). In America, arthritis and related conditions, such as osteoarthritis

cost the country almost $128 billion annually in medical care and indirect expenses,

including lost income and productivity. Between 1990 and 2010, disability due to

osteoarthritis in the UK had increased by 16% and expected continue to grow

(Nordqvist C., 2014).

The overall impact of the osteoarthritis on a person varies depending on the

joints involved, the degree of pain and extent of loss of use. When the hands are

affected, their daily activities will be affected, such as fastening buttons, writing and

6

even eating when the situation going worst. Osteoarthritis in the hips and knees will

restrict mobility, limit walking, climbing, and bathing. In serious cases, osteoarthritis

is a huge obstacle to people’s mobility and independence, and their tone of liveliness.

2.1.1 Causes

Osteoarthritis, also known as degenerative arthritis, degenerative joint disease,

or osteoarthrosis is a condition in which the joints of the body become damaged, stop

moving freely, and become painful (Arthritis Research UK, 2013). Degenerative

arthritis can be result from a combination of the partitioning of the joint and the body’s

attempted repair processes. The wearing away of the articular cartilage that covers the

ends of the bones in a joint will make the two bones (tibia and femur) rubs against each

other and become rough and thin. This degeneration also will affect the underlying

bone become thicker and lastly grows into the joint forming bony spurs (osteophytes)

which will make the gap between the bones become narrows. The inner layer of the

joint capsule (synovium) may thicken and make excess fluid, causing the joint to swell,

while the capsule and ligaments around the joint thicken and contact (Marlene F. et al).

In severe osteoarthritis, the loss of cartilage can result in bones rubbing against each

other and wearing away, as shown in Figure 2.1.

7

a. b.

c.

Figure 2.1: How osteoarthritis affects a joint a) A normal joint, b) A joint with

mild osteoarthritis, c) A joint that has been deformed by severe osteoarthritis.

Adapted from Arthritis Research UK

The causes of OA are still not yet fully understood. However, some factors that

can increase the risk of getting OA are known. The common risk factors include:

Age : The chance of getting OA rises after reach age 45 because the

ability to heal decreases as a person get older

Gender : women taking more risk to get OA compared to men

Obesity: Being overweight will cause excessive pressure on the knee

Previous joint injury or disease: improper joint surgery and joint

diseases may taking risk of OA

Heredity: genetic mutations will make a person more likely to develop

OA. It may also due to inherited abnormalities in the shape of the bones

that surround the knee joint

Occupation: Athletics and heavy duty workers that include a lot of

activity that can stress the joint, such as kneeling, squatting, or lifting

heavy weights are more likely to get OA

8

2.1.2 Diagnosis

Diagnosing arthritis early can prevent permanent damage. It is not always easy

to diagnose and can take several weeks or months to get a definitive diagnosis. Various

diagnostic tests are employed in the evaluation of OA. Basically, the GP (general

practitioner, primary care physician) will ask the patient about the symptoms, as well

as carrying out some physical examination and check their medical history (Sinusas et

al., 2012). Nowadays, there is no current and definitive test that can diagnose OA yet.

If the possible conditions are suspected, imaging diagnostics will be use such as plain

radiography (x-rays) and magnetic resonance imaging (MRI). However, the diagnostic

tests are restricted for pregnant women although the risk of radiation exposure to the

fetus are small.

X-ray is the most common use by the doctor to diagnose OA. An x-ray will

generate a very small amount of radiation to produce an image of the bones and tissues

surrounding a joint as shown in Figure 2.2. The GP will uses the X-rays to evaluate

arthritis. From the x-rays film, the GP can:

Rule out injury or other diseases of the joint

Have a baseline film for comparison while having treatment

Look at the structures of the joint

a. b.

Figure 2.2: Examples of image of knee joint by X-rays. a) Normal knee b) bone

spurs and narrowed joint space caused by osteoarthritis. Adapted from

Intermountain Medical Imaging, Boise, Idaho

9

MRI scans may be used when X-rays do not show a clear reason for joint pain

or when the X-rays suggest that other types of joint tissue could be damaged. MRI is

a test that uses a magnetic field and pulses of radio wave energy to make pictures of

organs and structures that are inside the body, as shown in Figure 2.3.

a. b.

Figure 2.3: Examples of image of knee joint by MRI. a) side view of the normal

knee. b) Side view of knee joint with a piece of meniscus that has been torn and

moved. Adapted from Intermountain Medical Imaging, Boise

2.1.3 Treatment

Treatment choices can be classify into four main categories: non-

pharmacologic, pharmacologic, complementary and alternative, and surgical. In

general, the safest and least invasive therapies will be the first choice before

proceeding to more invasive, expensive therapies. Basically, OA patients will receive

some treatment from the first two categories. If the situation of the patient declines,

surgical treatment would be considered (Stephen K. et al, 2010).

10

2.1.3.1 Non-pharmacologic

Non-pharmacologic therapy often starts with exercise. The researchers found

that the land-based exercise can relief knee pain and improve the physical function

within 24 months (Thomas et al,2002 ; Frasen & McConnell, 2008) but some

researchers found that the effects decline over time and finally disappear (Baar et al,

2001).

Therapeutic ultrasound is one of the non-pharmacologic treatment which is a

physical therapy modality that often used in OA treatment. A Cochrane review of this

modality concluded that although ultrasound therapy is almost certainly useful for

some patients, but it is not a reliable or evidence-based therapy (Rutjes AW, 2010).

Another types of non-pharmacologic treatments include bracing and splinting

to help support painful or unstable joints. A cane can help to support the body weight

of OA patients, but it needs to be properly fitted.

2.1.3.2 Pharmacologic

Pharmacologic treatment is the treatment by using medicine such as painkillers,

acetaminophen, Nonsteroidal anti-inflammatory drugs (NSAID), Opioids, steroids

injection and Hyaluronic acid injection. Pharmacological treatments for OA of the

knee have not been proven to change the progression of the disease, but may be

practiced as a pain reliever. Basically, the Acetaminophen or painkillers (e.g.

paracetamol) will be the first choice to relief the knee pain because it is inexpensive,

safe and effective (Sinusas et al, 2012). The U.S. Food and Drug Administration

recommends that the patient must instructed to take only 650 to 1,000 mg of

acetaminophen up to four times and no more than 4,000 mg per day to avoid liver

toxicity (Sinusas et al, 2012).