Design and Analysis of Affordable Artificial Knee Joint Model. Motion and Stress Analysis will be done on a digital model using SolidWorks

Page - 1 - of 89
Design and Analysis of Affordable Artificial Knee Joint Model. Motion and Stress
Analysis will be done on a digital model using SolidWorks
A Graduate Project Report
Submitted to
San José State University
In Partial Fulfillment
Of the Requirements for the Degree
Masters of Science in Engineering
GENERAL ENGINEERING
by
GAUTAM SINGH
FALL 2016

Page - 2 - of 89
ABSTRACT
Knee joint consists of different components, i.e. femur, tibia, patella and menisci which make
it a complex structure, undergoing different critical loads in human body performing motions
and physical activities. Amputation or limb loss has been a problem faced by humans for long.
Looking at a decade back, the major available resort to the amputees were walkers, crutches,
peg-leg or wheelchairs. Due to the major advancements in medical science and biomedical
design, a mechanical replacement of any such limb loss are present and it can be custom
designed based on any patient’s needs. The loss of limb can result due to the medical conditions
such as diabetes, peripheral arterial diseases which causes poor blood flow to the extremities,
or due to injuries such a burn, accidents or perhaps due to cancer. In any of such cases, the
affected arm or limb needs to be removed. One way to do that is through amputation. In order
to cope with after effects of amputation, many prosthetics have been designed. A prosthetic is
an artificial extension that replaces missing body part (upper or lower body extremity). It is
part of the field of biomechatronic (mechanical devices with human muscle, skeleton, and
nervous systems) to assist or enhance motor. However, one of the key difference or gap in the
design of knee prosthetic is the lack mechanics around knee movement. Some designs which
did consider knee movements cost higher amount.
In order to fil this gap, I have looked into many literature reviews and tried to design and create
my own knee joint using SolidWorks software. It includes understanding of SolidWorks,
designing and studying each part involved in knee motion and assembling the created part into
one to build a low-cost human knee joint. Later motion analysis has been performed in order
to check the weight bearing, movement and angles the knee joint can take into account.

Page - 3 - of 89
ACKNOWLEDGEMENTS
I would like to express my sincere gratitude to my supervisor, Lecturer/Consultant Dr. Ken Youssefi for
his positive attitude and constant support and also to my co-supervisor Dr. Raj E. Venkatesh for giving
me the opportunity and for his valuable guidance and unfailing support.
I would like to express my gratitude to San Jose State University Student Center, for giving me the
opportunity to use their Engineering Laboratory for using SolidWorks.
Finally, I express my gratitude to the God, my parents, family, friends and my roommate who have
always been a constant source of encouragement. To all the others who assisted me in one way or
another, I express my sincere gratitude.

Page - 4 - of 89
TABLE OF CONTENTS
ABSTRACT....................................................................................................................................I
ACKNOWLEDGMENTS................................................................................................................III
TABLE OF CONTENTS..................................................................................................................IV
LIST OF FIGURES........................................................................................................................VII
LIST OF TABLES...........................................................................................................................IX
LIST OF GRAPHS...........................................................................................................................X
CHAPTER 1: INTRODUCTION.......................................................................................................11
1.1 INTRODUCTION......................................................................................................................11
1.2 Background.......................................................................................................13
1.2.1 What is Knee and its Anatomy? ....................................................................13
1.2.2 Knee Joint and its Structure ..........................................................................15
1.2.3 Knee Joint Movement …………………................................................................16
CHAPTER 2: LITERATURE REVIEW ……………...................................................................................19
2.1 Prosthesis and its Types …………………..................................................................19
2.2 Knee Prosthesis History and its Development ….…………….………………………………22
2.2.1 Structure of Knee Joint .................................................................................22
2.2.2 Motion of Knee ………………………………………………………………………..………………23
2.2.3 Knee Joints Loads …………………………………………………………………………………….24
2.3 Total Knee Replacement …………………………………………………………………………………24
2.4 Prosthetic Knee ………………………………………………………………………………………………25
CHAPTER 3: MECHANICAL DESIGN ………………………………………..………………………………………………..30
3.1 Design Features …………………….………………………………………………………………………30
3.2 Mechanical System……………………………………………………………………….…………......31
3.3 Degrees of Freedom ……………………..………………………………………………………………34

Page - 5 - of 89
3.4 SolidWorks…………………………………………….………………………………………………...35
3.4.1 Proposed Design …………………………………………………………….………….………...36
3.4.2 SolidWorks Design – Parts …………………………………….……………………………...39
3.4.3 SolidWorks Design – Assembly ……………………………………………………………...41
CHAPTER 4: Results and Analysis ………………………………..…………………………………………………………43
4.1 Anthropometric Analysis ………………………………………………………………………...43
4.2 Stress Analysis ………………………..……………………………………………………………….45
4.3 Motion Analysis ……………………………….………………………………………………………57
4.3.1 Description of our Problem Statement ………………………………………………….57
CHAPTER 5: Conclusion and Future Works …………………………………………………………………………...62
REFERENCES………………………………………………………………………………………………………………………….69
APPENDICES...……………………………….…………………….………………………………………………………………....69
Appendix 1 Part Report…………….…………………………………………..…………………….73
Appendix 2 Assembly ………………………………………………………………………………...79
Appendix 3 Stress Analysis …………………………………….…………………………………..84
Appendix 4 Motion Analysis ………..……………………………………………………………89

Page - 6 - of 89
LIST OF FIGURES
Fig. 1: Patient with Below Knee Amputation …………………………………………………………………………….12
Fig. 2: Amputation in below knee joint..........................................................................................12
Fig. 3: Human Knee Joint (a) Anterior View (b) Posterior View (c) Cross sectional View ……………13
Fig. 4: The axes and planes of biological knee joint …………………………………………………………………..17
Fig. 5: Biological Knee planes …………………………………………………………………………………………………….17
Fig. 6: Trans-radial Prosthesis ……………………………………………………………………………………………………20
Fig. 7: Trans-humeral Prosthesis ……………………………………………………………………………………………….20
Fig. 8: Trans-tibia Prosthesis …………………………………………………………………………….……………………….21
Fig. 9: Trans-humeral Prosthesis …………………………………………………………………………………………..…..22
Fig. 10: Total knee Implant………………………………………………………………………………………………………..23
Fig. 11: Prosthetic Knee……………………………………………………………………………………………………………..24
Fig. 12: Force platform to calculate Ground Reaction Force……………………………………………………...26
Fig. 13: Load assessment on one Knee ……………………………………………………………………………...........31
Fig. 14: Four Bar Knees ……………………………………………………………………………………………………………...32
Fig. 15: Nabtesco 6-bar knee (P-MRS)……….……………………………………………………………………………..…33
Fig. 16: Single Axis Knee …………………………………………………………………………………………………………..…34
Fig. 17: Knee Joint Motion ………………………………………………………………………………………………………....34
Fig. 18: Top view of the Knee Joint Design ………………………………………………………………………………....36
Fig. 19: Final Version of Knee model …………………………………………………………..………………………….…..38
Fig. 20: (A) Dimensions of Part …………………………………………………………………………………….……………..39
(B) Mass properties of Part 1………………………….……………………………………………………………....39
(C) Part 3………………………………………………………………………………………………………………………….40
(D) Part 4………………………………………………………………………………………………………………….……..40
(E) Part 5…………………………………………………………………………………………………………………….…...40
(F) Part 6……………………………………………………………………………………………………………………..…..40
(G) Part 7……………………………………………………………………………………………………………………..….41

Page - 7 - of 89
Fig. 21: (A) Assembly of Part 1………………………….………………………………………………………………………..41
(C) Assembly of Part 3…………………………………………………………………………………………………….41
(D) Assembly of Part 4……………………………………………………………………………………………………41
(E) Assembly of Part 5………………………………………………………………………………………………......42
(F) Assembly of Part 6……………………………………………………………………………………………………42
(G) Assembly of Part 7……………………………………………………………………………………………………42
Fig. 22: Final Knee Model …………………………………………………………………………………………..……….….…..42
Fig. 23: (A) Original Model………………………………………………….....………………………45
(B) Analyzed Model …………………………………………………………………………………………………………45
Fig. 24: Knee Model Information………………………………………………………………………………………………….48
Fig. 25: Material Properties ………………………………………………………………………………………………………….50
Fig. 26: Load and Fixtures …………………………………………………………………………………………………............50
Fig. 27: Connector ………………………………………………………………………………………………………………………...51
Fig. 28: Mesh Information ………………………………………………..…………………………………………………………..53
Fig. 29: Solid Mesh (Knee Model)…………………………………………………………………………………………………..53
Fig. 30: Stress Analysis …………………………………………………………………………….…………………....................55
Fig. 31: Strain Analysis…………………………………………………………………………………………………………………..55
Fig. 32: Factor of Safety………………………………………………………………………………………………………………...56
Fig. 33: Human (knee) Position while sitting………………………………………………………………………………….57
Fig. 34: Face 1 and Face 2 are perpendicular to each other……………………………………………………………58
Fig. 35: Virtual position of motor…………………………………………………………………………………………………..58
Fig. 36: Moment analysis around knee…………………………………………………………………………………………..59
Fig. 37: (A) Leg (Tibia and Femur)…………………………………………………………………………………………………..59
(B) Knee Joint…………………………………………………………………………………………………………………….59
(C) Knee bonded with thigh acting as Human Femur………………………………………………………….59
Fig. 38: Units of the measurement…………………………………………………………………………………………………60
Fig. 39: Distribution of Stress on Knee Model…………………………………………………………………………………63
Fig. 40: Applied and Distributed Load on Knee Model……………………………………………………………………63

Page - 8 - of 89
LIST OF TABLES
Table 1: Functional Range of Motion of Human Knee ………………………………………………………15
Table 2: Study Properties ………………………………………………………………………..………………………..49
Table 3: Resultant Force……………………………………………………………..…………………………….………49
Table 4: Stress Analysis comparison with Knee model and Biological Knee Implant ….………53
Table 5: Motion Analysis Data for Knee model ………………………………………………………………….62
Table 6: Motion Analysis Data for Knee model…………………………………………………………………..64

Page - 9 - of 89
LIST OF GRAPHS
Graph 1: Torque vs Time …………………………………………..………………………………………………………..60
Graph 2: Torque and Angular Displacement vs Time ……………………..………………………………………61

Page - 10 - of 89
Chapter 1: INTRODUCTION
1.1 Introduction
Amputation or limb loss has been a problem faced by humans for long. Looking at a decade
back, the major available resort to the amputees were walkers, crutches, peg-leg or wheelchairs.
Due to the major advancements in medical science and biomedical design, a mechanical
replacement of any such limb loss are present and it can be custom designed based on any
patient’s needs. The loss of limb can result due to the medical conditions such as diabetes,
peripheral arterial diseases which causes poor blood flow to the extremities, or due to injuries
such a burn, accidents or perhaps due to cancer. In any of such cases, the affected arm or limb
needs to be removed. One way to do that is through amputation. Using surgery, the doctors
removes the affected extremity in order to treat the disease or injury. In some cases, where due
to infection, antibiotics fail to react, amputation surgery needs to be performed. As a result of
amputation surgery, the patients need artificial arms and limbs to do daily activities. There are
many devices that are used to recover from amputation surgery. The most commonly used is
prosthetic devices. An artificial extension that replaces missing body part (upper or lower body
extremity). It is part of the field of biomechatronic (mechanical devices with human muscle,
skeleton, and nervous systems) to assist or enhance motor. The type of artificial limb used is
determined largely by the extent of an amputation or loss and location of the missing extremity.
The knee amputation can be of two part – below knee amputation which is amputation
performed for ankle and foot related problems. [15] The below knee amputation usually leads
to artificial leg that can allow a patient to walk. [16]

Page - 11 - of 89
Figure 1: Patient with Below Knee Amputation
This is performed near the area between foot and ankle. This amputation provides good results
for a wide range of patients with many different diseases and injuries. [17]
Figure 2: Amputation in below knee joint

Page - 12 - of 89
For the above-knee amputee, the prosthetic knee joint is one of the most critical components
of the prosthesis. Any type of surgical operation that severs thigh section between the knee and
joint is known as above knee amputation. It generally happens when the amputee has gone
through some disease or accident leading to complete loss of foot and shaft sections. However,
the thigh section is partially lost. The purpose of my project is to study the review of previous
knee models and designs a knee joint which could benefit the patients such that the design
could replicate the human knee joint as much as possible. [1] Also, the knee model has to be
frugal so that patient and the amputees all around the world could benefit from it.
Modern prosthetics now provide wide selections of prosthetic knee joint. Each selection is
honed to wide selection of amputees covering specifications such as hydraulic, friction, lock,
safety. These single axis knees thus provide many advantages due to such specifications
mentioned before. [3] We will now study the background of knee, knee joints and its anatomy
to better under the biology of it before designing the human knee using SolidWorks.

Page - 13 - of 89
1.2 Background
1.2.1 What is Knee and it anatomy?
The knee is the largest joint in the human body and plays very important roles in
our daily lives. The knee is involved in virtually every daily function that we do, ranging from
walking to climbing to driving and to sitting. [1]
The knee joint is one of the most complex joint, but it might look like a simple joint to many
of us. Moreover, the knee is more likely to be injured than any other joint in the body. The knee
joint consists of a curved lower end of the thighbone (femur), which rotates on a curved upper
end of the shinbone (tibia), and the kneecap (patella), which slides in a groove at the end of the
thighbone. [1] The knee muscles which go across the joint are the quadriceps (front of the knee)
and the hamstrings (back of the knee). The ligaments are equally important in the knee joint
because these ligaments hold the bones together. Basically, the muscles move the joint while
the ligaments stabilize it. [1]
Figure 3: Human Knee Joint (a) Anterior View (b) Posterior View (c) Cross sectional View [1]

Page - 14 - of 89
Four main bones exist between the hip and ankle joints namely femur, patella, tibia, and fibula.
The longest and strongest bone of the human skeleton is femur. It extends from the pelvis
region to the knee region. Tibia and fibula are two long bones in the human leg between the
knee and ankle. Tibia is the interior and thicker region. The fibula is the exterior and thinner
one. The upper end of tibia joins femur to form the knee joint, which is the most complex joint
in the human body. The femur has two lower rounded ends called condyles. The one toward
the center of the body called the medial condyle, and the one to the outside called the lateral
condyle. Above the condyles on both sides are epicondyles which work as sites for muscle and
ligament attachment. The cruciate ligaments attach to the space between the two condyles
called intercondylar fossa. These Cruciate ligaments are the most important ligaments in the
knee joint. Their main function is serve to stabilize it and guide its motion. The patella, also
known as kneecap, protects the knee joint and increases the quadriceps lever arm thus allowing
the quadriceps to apply force to the tibia more effectively during extension. Patella is the
triangular-shaped bone. It is not connected to femur or tibia directly. They are in turn connected
to the femur by being contained within the patellar tendon that connects the quadriceps muscles
to the tibia. Fibula has no contact with the knee and attaches to the tibia by ligaments below
the tibia bearing surfaces of the knee.
1.2.2 Knee Joint and its structure
Human knee joint is synovial joint. It is defined by a joint cavity, articular cartilage and an
articular capsule consisting of a fibrous capsule lined with synovial membrane. The synovial
fluid provides lubrication of the human knee joint. The synovial fluid is secreted from the
synovial membrane, giving nearly frictionless motion. [2] The main surfaces of the joint, which
are covered in articular cartilage, are the convex medial and lateral condyles of the femur, the

Page - 15 - of 89
medial and lateral condyles of the tibia, also known as the tibial plateau, and the posterior
surface of the patella. [2]
Human knee joint is stabilized by four separate ligaments. Medial collateral ligament (MCL)
and lateral collateral ligament (LCL) lie on the sides of the joint. These two ligaments mainly
stabilize the joint in a lateral – medial direction. In the front part of the knee joint center, there
is the anterior cruciate ligament (ACL), which is very important femur stabilizer. Another most
important function is to prevent rotating and sliding forward tibia during jumping and
deceleration activities. Directly behind the ACL is its opposite, the posterior cruciate ligament
(PCL). Main function of the PCL is to prevent the tibia from sliding to the rear part of a knee.
[1]
1.2.3 Knee Joint Movement
The biological knee joint is having three axes and planes of rotation. The anatomical planes
allow for position/orientation representation of the knee in any of its three original planes. The
line connecting medial and lateral femoral condyles outlines flexion-extension motion (phi
angle). [3] The line along the tibia governs the axis of rotation for the internal-external angle
(psi angle). The perpendicular axis to the other two axes states as the abduction-adduction angle
(theta angle). [3]

Page - 16 - of 89
Figure 4: The axes and planes of biological knee joint [3]
The median plane (sagittal) is an upright plane passing from front to back. The median plane
separates the body into right and left halves. [3]
The front plane (coronal) is the perpendicular plane running from side to side. This coronal
plane splits the body into anterior and posterior parts.
The horizontal plane (transverse) is a flat plane, which divides the body into upper and lower
regions. [3]
Figure 5: Biological Knee planes [3]

Page - 17 - of 89
The human knee has various sets of motion along with the movement involved. Some of the
important motions and knee analysis terms are defined below.
(a) Translational or Translation motion is the movement of element along a straight line.
(b) Rotation or Rotational motion is a movement about a pivot point.
(c) Centre of Rotation is the point about which rotation movement occurs.
(d) Single Axis Knee is any knee in which the shin moves in pure rotation about center of
rotation.
(e) Polycentric knee is any knee whose designs allow the shin to move in a combination of
rotational and translational motion.
(f) Instantaneous center of rotation of Instant center is the point about which shin tends to move
in pure rotation at any given instant of motion.
(g) Four bar linkage knee is a polycentric knee design. It has four elements each joined at four
different points. These four elements are thigh, shin and two links.
(h) Six bar linkage is designed to have more instant inactive joints than a four-bar linkage,
hence making the prosthetic knee more stable in the standing phase.

Page - 18 - of 89
Chapter 2: Literature Reviews
2.1 Prosthesis and its Types
When a person becomes a limb amputee, he or she is faced with confounding emotional and
financial lifestyle changes. The amputee requires a prosthetic device(s) and services which
become a life-long event. A prosthesis is an artificial extension that replaces a missing body
part such as an upper or lower body extremity. It is part of the field of biomechatronics, the
science of fusing mechanical devices with human muscle, skeleton, and nervous systems to
assist or enhance motor control lost by trauma, disease, or defect. An artificial limb is a type
of prosthesis that replaces a missing extremity, such as arms or legs. The type of artificial limb
used is determined largely by the extent of an amputation or loss and location of the missing
extremity. Artificial limbs may be needed for a variety of reasons, including disease, accidents,
and congenital defects. [5]
There are four main types of artificial limbs. These include the trans-tibia, trans-femoral, trans-
radial, and trans-humeral prostheses:
A trans-radial prosthesis is an artificial limb that replaces an arm missing below the elbow.
Two main types of prosthetics are available. Cable operated limbs work by attaching a harness
and cable around the opposite shoulder of the damaged arm. The other form of prosthetics
available are myoelectric arms. These works by sensing, via electrodes, when the muscles in
the upper arm moves, causing an artificial hand to open or close. [5]

Page - 19 - of 89
Figure 6: Trans-radial Prosthesis [16]
A trans-humeral prosthesis is an artificial limb that replaces an arm missing above the elbow.
Trans-humeral amputees experience some of the same problems as trans-femoral amputees,
due to the similar complexities associated with the movement of the elbow. This makes
mimicking the correct motion with an artificial limb very difficult. [5]
Figure 7: Trans-humeral Prosthesis [16]
A trans-tibia prosthesis is an artificial limb that replaces a leg missing below the knee. Trans-
tibia amputees are usually able to regain normal movement more readily than someone with a
trans-femoral amputation, due in large part to retaining the knee, which allows for easier
movement. [5]

Page - 20 - of 89
Figure 8: Trans-tibia Prosthesis [16]
A trans-femoral prosthesis is an artificial limb that replaces a leg missing above the knee.
Trans-femoral amputees can have a very difficult time regaining normal movement. In general,
a trans-femoral amputee must use approximately 80% more energy to walk than a person with
two whole legs. [5] This is due to the complexities in movement associated with the knee. In
newer and more improved designs, after employing hydraulics, carbon fiber, mechanical
linkages, motors, computer microprocessors, and innovative combinations of these
technologies to give more control to the user. Usually, the type of prosthesis depends on what
part of the limb is missing. [5]

Page - 21 - of 89
Figure 9: Trans-femoral Prosthesis [16]
An important thing is to consider that the prosthetic must be able to withstand rigorous physical
demands while also being light enough and durable for prolonged use. This leads to increase
in material cost which causes cost to go quite up. One way to do is to minimize on the material
leading to comptonization in building materials.
2.2 Knee Prosthetic History and Development
Apart from emotional and physical penalties, management of amputation is a high-priced
treatment. Straight cost of lower extremity amputation ranges from $20,000 to $60,000
depending on the degree of the amputation (e.g. toe amputation vs. trans-femoral amputation).
[8] Along with the amputation surgery and associated hospitalization costs, amputees need
prosthetic devices to achieve a certain degree of mobility. Accouterment costs range from a
few thousand dollars for the passive models (Mauch Knee: $5,200, (Össur, Iceland)), [17]
about $25,000 for micro-processored models (Plie MPC: $18,475 (Freedom Innovations, CA,
USA), C-leg: $20,000, (Otto Bock, Germany), Rheo Knee: $30,000, (Össur, Iceland)) and

Page - 22 - of 89
$100,000 for the powered models (Power Knee: $100,000, (Össur, Iceland)). [8] [17]
Currently, prosthetics technology has come a long way compared to Paré’s mechanical device
by using hydraulic, pneumatic and electrical/computer controlled elements in order to
minimize the consequences of passive mechanisms (Zissimopoulos, 2007; Struyf, 2009; Kuo,
2007). Nevertheless, with the exception of Össur’s Power Knee (Össur, Iceland), [17] [8]
despite the increasing sophistication of prosthetic knee technology, the majority of the
prostheses are controlled damping systems, which replicate the negative work functions of a
biological knee, but cannot contribute positive work to gait (Martinez- Villalpando, 2009). The
emerging prosthetic knee designs [6] elaborate the importance of efficient energy flow at the
knee joint by harvesting/returning energy in a spring. A spring not only permits significant
power demand reduction by providing energy storage capacity but also allows high power-to-
weight ratio [7] [8] [54]
Therefore, instead of using heavy motors, gearboxes and bulky batteries, a spring can
help the peak power demand of the prosthesis, by producing the needed positive energy during
the stance phase with less weight. In this work, the significance of energy flow in trans-femoral
amputee gait was explored along with recent developments, which emphasize harvesting/
returning energy in a spring by compressing/releasing it controllably during gait. However,
constant spring stiffness is suboptimal to varying gait requirements for different types of daily
activity as suggested by Pfeifer in 201. This is due to the variability of the impedance functional
stiffness and the power requirements of the knee caused by the passive characteristics, viscous
and elastic attributes and the activation dependent properties of the muscles in the joint. [8]
[54] As it is not realistic to replace the energy storage element of the prosthesis for each
performed activity, the efficiency of the spring should be supplemented by smart systems such
as microprocessors, valves, pumps, motors etc. through adjusting the amount and timing of the
spring compression/release depending on the biomechanical demands of the performed

Page - 23 - of 89
activity. Nonetheless, for more efficient prosthetic knee design process, mimicking of the
healthy human knee functional stiffness is necessary for providing the desirable quantitative
values for loading and unloading intervals, which match the biomechanical demands of the
performed activity to the best extent possible. [8] [54]
2.3 Knee Replacement Implant
When there occurs any damage in any bone or any joint parts of human body, to overcome
those defective organs people generally prefer replacement of those with an specific artificial
organ or as we can say implant as prescribed by the surgeon and going through an operative
method. Knee replacement can be done by total knee replacement or some people get benefited
with partial knee replacement. Implants are generally made up of metals, metal alloys, strong
plastic materials, ceramic material which can be implanted in our body, to make the joint
strengthened strong polymeric material like acrylic paste [9] [54].
Implant Design:
There are several kinds of implant designs for knee replacement implants. As we know knee
joint is a type of hinge joint because with the help of knee joint different motion as be performed
by the leg like straightening and bending of legs [9] [54]. There lots of flexion and extension
motions are being carried out in the knee joint, which makes it a complex structure, were
surfaces if bone generally glides and roll over each other. Accounting on this function of knee
first implant designed was the hinge i.e. a connecting hinge was placed in between the parts of
the knee joint. Newer implants were designed according to the complexity, durability,
biocompatibility, its tensile strength etc. and to design it in such a manner so that it can mimic
the actual functioning of the normal knee functions. Some of the implant models were designed
modeled to preserve the actual ligament of the patient where as other parts were replaced by
an artificial organ. Now days in the market area there are about 150 models of knee replacement

Page - 24 - of 89
implants design. Recent designed knee implant mostly focused on the gender specificity.
According to different studies and research it was found that the portions and shape of women’s
knee is different from man’s knee structure. So, may manufacturers design knee implant with
a attach thighbone component at the end so that it can easily match the knee structure of women
knee joint. It provides better functioning than any standard implant [10] [54]. Right choice of
implant design can be used after the specification given by the doctor or surgeon according to
the brand and model design as referred to one’s weight, age, and health and activity level. [54]
2.4 Prosthetic Knee
2.4.1 Different types of Prosthetic Knee
Passive Knees
The knee joint is the most crucial part of lower limb. Muscle action provides power for a
biological knee in two ways; the active force is applied by muscles contraction; also, variable
stiffness is provided by muscles. Only the latter action is used in “passive” prosthetic knee.
Passive prosthetic knees can be categorized into two groups: simple-passive and semi-passive.
There is no automated control over prosthesis stiffness in simple passive knees. However, the
level of stiffness can be adjusted manually. During the weight bearing, the leg can be kept from
buckling and stumbling by means of i) manual lock, ii) weight activated stance mechanisms,
iii) fluid resistance, or iv) polycentric mechanism. One manual locking knee is presented in
Figure 12 (a). A remote release cable is utilized in this device to provide stability in knee
extension. This device leads to high energy cost during ambulation. In weight-activated knee,
a constant-friction is used to provide high stability during the stance phase. Transferring the
body weight to the knee activates an embedded brake that prevents buckling. This brake will
release when the knee becomes unloaded. However, a constant friction still presents during the
swing phase which results in inefficient gait. An energy storing element such as spring can also

Page - 25 - of 89
accompany the knee during the swing phase. It is loaded in weight bearing and is released
during swing phase. An example of this type of prosthesis is depicted in Figure 12 (b). Fluid
resistive knees consist of hydraulic or pneumatic cylinders to provide variable resistance.
Therefore, amputee would be able to have different walking speed. Piston of the cylinder is
attached to a hinge joint in the thigh section behind the knee joint. From the other end, cylinder
is connected to a pivot in shank. Hydraulic knees are more efficient than pneumatic ones.
However, the pneumatic knees are lighter, cheaper, and cleaner than hydraulic ones.
Polycentric knees have multiple axes of rotation. These prosthetic devices are kinetically
locked during mid-stance and provide stability. An example of polycentric knees is depicted in
Figure 12(c). To provide variable walking speed for amputees, pneumatic or hydraulic cylinder
can be embedded in polycentric knees. The aforementioned “simple-passive” knees are low-
cost compare to the other types of prosthetic knees. Therefore, most consumers of these devices
are children since they need to change their prostheses as they grow up.
Figure 12: (a) manual locking knee (3R39, Otto Bock Healthcare GmbH) (b) weight-activated
knee (3R38, Otto Bock Healthcare GmbH) (c) Polycentric knee (3R66, Otto Bock Healthcare
GmbH) [9]
In a microcontroller based passive knee joint, the controller changes the knee impedance
(damping and/or stiffness) based on sensory information. This resistive torque for the knee
joint can be provided by electric brakes, or by hydraulic, pneumatic, Magneto-Rheological

Page - 26 - of 89
(MR) dampers. These types of knee joints are called “semi-passive” prostheses since their
stiffness can be altered by the controller.
Aeyels et al [21] developed the first micro-controller based knee joint which comprised of an
electromagnetic brake. A gear box accompanies the brake to increase the applied resistive
torque to 50 Nm. The resistive moment is varied continuously based on the sensory information
from the remnant stump and prosthesis state.
The hydraulic damper with variable impedance comprises a double acting cylinder where two
sides of the piston are connected through a valve. The commands determine the position of a
valve that controls the flow of oil from one chamber to the other [22]. The drawback of
hydraulic based knees is the presence of a minimum level of damping during all phases of the
gait cycle, even when it is not needed. Carlson et al [23] and Kim et al [24] replaced the
hydraulic damper with an MR damper to achieve a faster response for different speeds of the
gait cycle. The problems with MR dampers are their susceptibility to: degradation of the MR
fluids, sealant failure, leakage, and performance problems as well as high cost for commercial
applications.
1.4.2 Active Knees
Although lower limb prostheses have traditionally been passive, there have been attempts at
providing active versions.
Most of the developed hydraulic and pneumatic powered knees are tethered to an external
power supply because associated prostheses suffer from high energy consumption. Flowers
and Mann [23] and Stein and Flowers [25] suggested a powered electro-hydraulic knee joint
tethered to a power source. They used a hydraulic cylinder controlled by a 4/3 servo valve to
actuate the knee. Recently, Sup [26] developed a pneumatically actuated powered-tethered
lower limb which is controlled by a computer to alter the impedance of the actuators.

Page - 27 - of 89
One of the commercialized pneumatic knee joints is Intelligent Prosthesis, IP, (Chas A.
Blatchford and Sons, Ltd.). A pneumatic cylinder is employed to provide the rotary motion of
the knee joint during the swing phase. One stepper motor is used to adjust the position of a
needle valve (orifice) which controls the flow rate between two sides of the piston. The stepper
motor is controlled by a microcontroller based on the sensory information according to the
swing speed of the prosthetic leg. Buckley et al [26] revealed rationale for the commercialized
IP when they compared the energy cost of the IP and conventional artificial knee joint.
Although IP is not tethered like the other aforementioned hydraulically/pneumatically actuated
knee joints, its utilized system mobilized the knee joint only during the swing phase.
Wang et al [27] proposed a hydraulic system, which compresses the fluid in an accumulator
during stance, and then energizes and controls the knee during swing by using a needle valve.
The hydraulic circuit consisted of an accumulator, two cylinders (one for the ankle joint and
one for the knee joint), and two flow control valves. Also, the motion of the ankle joint causes
the motion of a piston in an ankle cylinder. This piston is connected to a control rod that
switches the shut valve to control fluid flow from the knee cylinder to the accumulator. A
stepper motor actuates a needle valve which controls the flow rate between accumulator and
knee cylinder. The problems of low efficiency and large size are the main flaws of the
aforementioned system.
It is worth noting that Saito [28] developed a tethered lower limb active orthosis equipped with
a bilateral-servo actuator to mimic the function of a bi-articular muscle. Orthosis is an added
support mechanism, usually a brace, to help a disabled person function. Saito accomplished
such task by using master and slave hydraulic cylinders. A ball screw mechanism accompanied
with a stepper motor controlled the master hydraulic cylinder. The slave side system comprised
of a cylinder and two piston rods acts as a bi-articular muscle. Both master and slave cylinders
can be controlled by open-shut solenoid valves.

Page - 28 - of 89
Sawicki et al [20] proposed a wearable bilateral lower limb orthosis. They used pneumatic
artificial muscles attached to the orthoses to provide flexion and extension torque at individual
joints. Although these pneumatic artificial muscles are light-weight and suitable for lower limb
exoskeleton and orthosis, they cannot generate enough power for fully active lower limb
prosthesis.
Recently, Kapti and Yucenur [21] proposed a tethered fully active knee powered by an electro
motor and a gear reduction system. They tried to decrease the user‟s energy cost by providing
a fully powered trans-femoral joint. Popovic et al [22] presented a methodology to determine
the optimal motor size for a motorized prosthetic knee.

Page - 29 - of 89
Chapter 3: Mechanical Design
Individuals with lower limb amputation have shown to expend more metabolic energy than an
individual with a healthy leg during normal walking. Walters in 1976 reported that trans-
femoral amputees expend up to sixty percent or more and Colborne in 1992 reported that trans-
tibial amputees tend to expend twenty to thirty percent more metabolic energy in normal
walking. Currently, most of the commercial prostheses available are passive prostheses. These
are not able to bring positive work at phase stance, causing risk to joint and back pain. Some
researchers have shown that powered prostheses for lower limb are able to mimic human gait.
They can provide negative and positive work in the stance phase as well as to improve amputees
performance in a more natural gait and normal walking.
Ideally a good prosthetic design need to have some important characteristics: They include
(a) Show be able to produce sufficient power to gait i.e. human motion
(b) Energy consumption should be very low to lowest
(c) It should fit properly i.e. should not exceed amputees’ limb or arm
Many prosthetic devices are now equipped with elastic elements. They help in increase
tolerance to load impact, proper storage and release of energy, as well as reducing energy
requirements with an increase power output.
3.1 Design Features
One of the important functional requirement of any knee design is its ability to replicate joint
motion as closely as possible. Compromise on any motion or degree of freedom will a sub-
optimal design. The following are major functional requirements for the design of knee
prosthesis: (a) able to bear load of human upper body weight, (b) can provide knee motion
similar to biological knee (c) should be able to hold under stress and strain. The thickness needs

Page - 30 - of 89
to be as uniform as possible to avoid any concentrated stress failure. Also, the maximum force
acting on the knee joint shall be the impact load while running. Considering the normal load
on the one side of knee joint to be half of total load of body weight such that load is equally
distributed. Then the maximum stress can be calculated as:
𝜎 =
𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑀𝑜𝑚𝑒𝑛𝑡 (𝑀)𝑥 𝑑𝑒𝑓𝑙𝑒𝑐𝑡𝑖𝑜𝑛 (𝑦)
𝑀𝑜𝑚𝑒𝑛𝑡 𝑜𝑓 𝐼𝑛𝑒𝑟𝑡𝑖𝑎 (𝐼)
Figure 13: Load assessment on one Knee
Bending Moment (M) = (patient weight/2) * moment arm (shaft size)
σ = maximum stress
deflection (y) = thickness/2 where thickness is based on the weight of patient
moment of inertia (I) = bh3
/12
Therefore, by substituting the value of each parameter, we can calculate the maximum stress it
can hold. This shall be done on the final model using SolidWorks.
3.2 Mechanical System

Page - 31 - of 89
mentioned before.
(a) Mechanical Four Bar Knee:
The knee prosthesis has a four-bar linkage arrangement at the knee, by which the motion can
be transmitted from the thigh to foot during squatting action and during swing phase of
walking. These are specific class of polycentric knees. The knee is characterized by four
elements joined at thigh, shin and two links. Knee flexion angle achieved is 150 deg.
Figure 14: Four Bar Knees [18]
Benefits of four bar linkage knee includes natural and smooth swing phase, stable stance phase,
low weight and compact design.
(b) Mechanical Six Bar knee: Fundamental types of six bar mechanism are Watt type and
Stephenson type. Ortho-europe developed Nabtesco 6-bar knee (P-MRS) provides
natural stance flexion from heel contact to mid stance. This feature results in absorbing
shock a heel strike. They also have added hydraulic cylinder in P-MRS system which
enhances walking during stance and swing phase by working as a shock absorber.

Page - 32 - of 89
Figure 15: Nabtesco 6-bar knee (P-MRS) [18]
(c) Single Axis knee: The swing block is connected to the upper joint section through the
swing axis and with the lower joint section through the knee axis and acts as a load-
dependent brake. This together with proper knee alignment secures the stance phase.
To control the swing phase, the axis friction and the spring force of the extension assist
are adjustable.
Figure 16: Single Axis Knee [18]
Our Knee model design includes the single axis knee. The reason being it is simple and cost
effective solution for low activity to requiring maximum stance security.

Page - 33 - of 89
3.3 Degrees of Freedom
The biological knee has six degrees of freedom. These are three rotational and three
translational.
(a) Rotation:
- The flexion and extension has up to 160 degree of flexion. Negative 5 degree (185
degree) in terms of hyperextension.
- Varus and Valgus has 6-8 degree in extension
- Internal-external rotation has 25-30 degree in flexion
(b) Translation:
- Anterior-posterior has 5-10 mm
- Compression has 2-5 mm
- Medio-lateral has 1-2 mm
Figure 17: Knee Joint Motion [12]

Page - 34 - of 89
The overall number of degree of freedom of the system can be calculated using the following
equation: [3]
𝑀 = 3(𝑛 − 1) − 2𝑓1 − 𝑓2
where M represents the degrees of freedom for the overall system, n, the total number of fixed
link segments, f1, the joints with one degree of freedom (DOF) and f2, the joints with two
degrees of freedom. The overall knee system is found to have 5-DOF, where the main knee
joint has 1-DOF. The human knee in comparison has 6-DOF, a much more complex system.
However, to maintain mechanical durability and remain within the bounds of a low-cost device,
the knee joint is simplified to a hinge-type 1-DOF mechanism. It contains three anatomically
equivalent parts – the upper tibia, knee joint and the moment arm that represents the active
knee joint [3]
Table 1: Functional Range of Motion of Human Knee
Activities Knee Flexion
Normal gait/Level Surfaces 60 deg
Stair Climbing 80 deg
Sitting/Rising from chair 90 degree
Sitting/Rising from toilet seat 115 deg
Advanced function > 115 deg
3.4 SolidWorks
SolidWorks 2016 was used to design the various components of the knee model. The San Jose
State University student laboratory was used to develop the design. CAD stands for Computer-

Page - 35 - of 89
Aided Design. It is very power tool in designing 2-D or 3-D images of physical object. CAD
are divided into two types – AutoCAD and SolidWorks.
AutoCAD are mainly used in civil engineering for designing bridges and buildings.
SolidWorks are mainly focused into electrical engineering and Biomedical engineering.
SolidWorks is what we call a "parametric" solid modeller used for 3-D design. Parametric
means that the dimensions can have relationships between one another and can be changed at
any point during the design process to automatically alter the solid part and any related
documentation (blueprint).
3.4.1 Proposed Design
The design proposed includes the knee joint and it extension which joins to shaft below the
knee to ankles and thigh above the knee.
Figure 18: Top view of the Knee Joint Design

Page - 36 - of 89
mentioned before.
Apart from that, literature research showed that by using hydraulic cylinder (as in P-MRS
system) enhances walking during stance and swing phase by working as a shock absorber. But
the application of hydraulics will result in higher cost. The alternative to hydraulic cylinder
was to apply spring system. A spring not only permits significant power demand reduction by
providing energy storage capacity but also allows high power-to-weight ratio [7] [8]
Therefore, instead of using heavy motors, gearboxes and bulky batteries, a spring can
help the peak power demand of the prosthesis, by producing the needed positive energy during
the stance phase with less weight. In this work, the significance of energy flow in trans-femoral
amputee gait was explored along with recent developments, which emphasize harvesting/
returning energy in a spring by compressing/releasing it controllably during gait. Applying
such knowledge to our design shown above in figure (19), we can redesign it to a new version
as shown below.

Page - 37 - of 89
Figure 19: Final Version of Knee model
The size of the spring was kept small to avoid any sideways movement which could cause
stress-strain leading to its breakage.

Page - 38 - of 89
3.4.2 SolidWorks Designs – Parts
Figure 20 (a): Dimensions of Part 1
Figure 20 (b): Mass properties of Part 1

Page - 39 - of 89
Figure 20(c): Part 2 Figure 20(d): Part 3
Figure 20 (e): Part 4 Figure 20 (f): Part 5

Page - 40 - of 89
Figure 20 (g): Part 6 Figure 20 (h): Part 7
3.4.3 SolidWorks Designs – Assembly
Figure 21(a): Assembly of parts 1,2,3,6 Figure 21(b): Assembly of parts 1,2,3,7

Page - 41 - of 89
Figure 21(c): Assembly of parts 1,2,3,7,5 Figure 21(d): Assembly of parts 1,2,3,7,5,6,4
Figure 22: Final Knee Model

Page - 42 - of 89
Chapter 4: Result Analysis and Discussions
4.1 Anthropometric Analysis
In order to perform motion analysis, proper gathering of data needs to be done. The data
measurement was obtained using human subject’s biological knee design. In my case of study,
I used the measurements similar to my knee model. The mass of the subject was 85kgs. The
maximum mass which was accessed was 112 kg and minimum mass assessed was 71 kg. The
height of the subject was 6 feet 3 inches which is 190 cm. The force exercised on human leg
was approximately equal to F= (m*g)/2= (84kg*9.8)/2= 412N. Based on this, maximum force
exerted was taken to be 550 N and 350 N. The length for both leg was assumed to be equal and
was equal to 0.863 m. The torque exerted was equal to Torque, T=F*L*Sin(theta) with
F=412N,
Leg length, L = 0.8636metre,
Knee angle, theta = 180 deg, so SIN(theta)=1
Therefore, Torque, T=412*0.8636*1 = 355.8 Nm
So, Torque required on standing as a function of knee angle= 355.5 Nm at Force=412N
Max Torque = F(max)*L*sin(theta)= 550*0.8636*1 = 474.98Nm
Min Torque = F(min)*L*Sin(theta)=350*0.8636*1 = 302.26 Nm
The movement starts with the knee at ninety degrees (or close to that) in the deep squat, and
ends with the knee angle at zero degrees when standing.

Page - 43 - of 89
Now if we want the amputee using this prosthesis to stand up in 1 second, then the average
angular velocity will be 90 deg/sec. Since, the start and end velocity equals to zero, so the peak
angular velocity will probably be 90*2 = 180 deg/sec.
=> 360 deg = 1 revolution per sec
=> 180 deg = 0.5 revolution per sec
=> 0.5 revolution per sec
=> 0.5 * 60 = 1 sec* 60
=> 30 revolutions per min
So, we have approximately 30 revolutions per minute (RPM=30)
Angular velocity, ω =30 RPM = 30*2π/60 = 3.142 rad/sec
Power generated, P= Torque * Angular velocity = 355.8*3.142 = 1117.93 watts
So, our human knee design generated power equal to 1117.93 watts.
When this power generation is compared to Seimen Motors (Z39-LE90SM4P), it produces
equal to 53 RPM and can deliver torque up to 199 Nm which generates power of 1256 watts.
To incorporate this design in human prosthetic knee, the speed of motor is kept low by Seimens
motors. This is because human muscles (electric motors) delivers lower force at higher speed.
By using this knowledge, spring was incorporated in the design where the joints move. This
method of design is called ‘series-elastic actuator’. Other way is to put elasticity in foot, which
is usually done in BIOM foot.
Spring stiffness takes was equal to 0.024Nm/Kg-deg [8]. Material selected was Cobalt-
Chromimum having elastic modulus equal to 7-30 MPa, and a density equal to 8.5g/cm3.

Page - 44 - of 89
4.2 Stress Analysis
Figure 23(a): Original Model Figure 23(b): Analyzed Model
Model Information:
Before performing stress analysis in SolidWorks, we need to model the system. Based on our
assumption of materials and measurements, the SolidWorks determine the volumetric
measurement as well as weight analysis of the parts designed.
Linear stress analysis with SolidWorks simulation enables engineers to quickly and efficiently
validate quality, performance, and safety—all while creating their design.
Linear stress analysis calculates the stresses and deformations of geometry given three basic
assumptions: (1) The part or assembly under load deforms with small rotations and
displacements. (2) The product loading is static (ignores inertia) and constant over time. (3)
The material has a constant stress strain relationship (Hooke’s law). SolidWorks simulation
uses finite element analysis (FEA) methods to discretize design components into solid, shell,

Page - 45 - of 89
or beam elements and uses linear stress analysis to determine the response of parts and
assemblies due to the effect of:
Forces
Pressures
Accelerations
Temperatures
Contact between components
Loads can be imported from thermal, flow, and motion Simulation studies to perform
multiphysics analysis.

Page - 46 - of 89
Model name: KneeModelel
Current Configuration: Default
Solid Bodies
Document Name and
Reference
Treated As Volumetric Properties
Document Path/Date
Modified
Fillet1
Solid Body
Mass:0.155208 kg
Volume:2.01569e-005 m^3
Density:7700 kg/m^3
Weight:1.52104 N
C:UserssggauDesktopAhm
ed2.SLDPRT
Nov 23 04:51:20 2016
Boss-Extrude2
Solid Body
Mass:1.68352 kg
Volume:0.000218639 m^3
Density:7700 kg/m^3
Weight:16.4985 N
ed3.SLDPRT
Nov 23 04:51:26 2016

Page - 47 - of 89
Revolve2
Solid Body
Mass:0.0647815 kg
Volume:8.41319e-006 m^3
Density:7700 kg/m^3
Weight:0.634859 N
ed4.SLDPRT
Nov 23 04:51:29 2016
Cut-Extrude1
Solid Body
Mass:0.0112543 kg
Volume:1.4616e-006 m^3
Density:7700 kg/m^3
Weight:0.110292 N
ed5.SLDPRT
Nov 23 04:51:33 2016
Kes-Ekstrüzyon2
Solid Body
Mass:0.149435 kg
Volume:1.94071e-005 m^3
Density:7700 kg/m^3
Weight:1.46446 N
ed6.SLDPRT
Nov 23 04:51:41 2016
Cut-Extrude3
Solid Body
Mass:8.45831 kg
Volume:0.00109848 m^3
Density:7700 kg/m^3
Weight:82.8914 N
edfoot.SLDPRT
Nov 23 04:50:51 2016
Boss-Extrude1
Solid Body
Mass:0.273048 kg
Volume:3.54607e-005 m^3
Density:7700 kg/m^3
Weight:2.67587 N
edrood.SLDPRT
Nov 23 04:50:58 2016
Figure 24: Knee Model Information

Page - 48 - of 89
Table 2: Study Properties
Study name Static 1
Analysis type Static
Mesh type Solid Mesh
Thermal Effect: On
Thermal option Include temperature loads
Zero strain temperature 298 Kelvin
Include fluid pressure effects from
SOLIDWORKS Flow Simulation
Off
Solver type FFEPlus
Inplane Effect: Off
Soft Spring: Off
Inertial Relief: Off
Incompatible bonding options Automatic
Large displacement Off
Compute free body forces On
Friction Off
Use Adaptive Method: Off
Result folder SOLIDWORKS document
(C:UserssggauDesktopSolidoworks - Practice)
Table 3: Units of measurements used
Unit system: SI (MKS)
Length/Displacement mm
Temperature Kelvin
Angular velocity Rad/sec
Pressure/Stress N/m^2

Page - 49 - of 89
Model Reference Properties Components
Name: Alloy Steel
Model type: Linear Elastic Isotropic
Default failure
criterion:
Max von Mises Stress
Yield strength: 6.20422e+008 N/m^2
Tensile strength: 7.23826e+008 N/m^2
Elastic modulus: 2.1e+011 N/m^2
Poisson's ratio: 0.28
Mass density: 7700 kg/m^3
Shear modulus: 7.9e+010 N/m^2
Thermal expansion
coefficient:
1.3e-005 /Kelvin
SolidBody 1(Fillet1)(2-1),
SolidBody 1(Boss-
Extrude2)(3-1),
SolidBody 1(Revolve2)(4-1),
SolidBody 1(Cut-Extrude1)(5-
2),
SolidBody 1(Kes-
Ekstrüzyon2)(6-1),
SolidBody 1(Cut-
Extrude3)(foot-1),
SolidBody 1(Boss-
Extrude1)(rood-1)
Curve Data:N/A
Figure 25: Material Properties
Fixture name Fixture Image Fixture Details
Fixed-1
Entities: 4 face(s)
Type: Fixed Geometry
Resultant Forces
Components X Y Z Resultant
Reaction force(N) -891.47 251.541 7.341 926.308
Reaction Moment(N.m) 0 0 0 0
Figure 26: Load and Fixtures

Page - 50 - of 89
Load name Load Image Load Details
Force-1
Entities: 7 face(s)
Type: Apply normal force
Value: 412 N
Figure 27: Connector
Calculation of Spring stiffness:
The embedded springs not only must provide the vertical displacement for the hip joint, but
also must act as a shock absorber against the ground reaction impact. In order to choose a
correct spring, stiffness of the spring is calculated using Hooke’s Law:
𝐹 = 𝑘𝑥 𝑜𝑟 𝑘 =
𝐹
𝑥
Spring needs to resist half of the Ground Reaction Force (GRF) since one leg is being
considered. The displacement of the spring is equal or less than the displacement of the hip
Connector Name Connector Details Connector Image
Spring Connector-1
Entities: 2 vertex(s)
Type: Spring(Two
locations)(Compres
sion & Extension)
Axial stiffness value: 0.024 N/m
Tangential Stiffness: 0.024 N/m
Rotational stiffness
value:
0 N.m/rad
Pre-compression value: 2.2e+006 N
Spring Connector-1

Page - 51 - of 89
joint, which is 71 mm. [19] The ground reaction force is 412 N. Therefore, the optimal stiffness
of the spring is 0.0024 N/m has been taken.
Mesh Information:
Contact Contact Image Contact Properties
Global Contact
Type: Bonded
Components: 1 component(s)
Options: Compatible
mesh
Total Nodes 149115
Total Elements 92224
Maximum Aspect Ratio 43.566
% of elements with Aspect Ratio < 3 98.4
% of elements with Aspect Ratio > 10 0.0813
% of distorted elements(Jacobian) 0
Time to complete mesh(hh;mm;ss): 00:00:09
Computer name:
Figure 28: Mesh Information
Mesher Used: Curvature-based mesh
Jacobian points 4 Points
Maximum element size 12.9024 mm
Minimum element size 0.645118 mm
Mesh Quality High
Remesh failed parts with incompatible mesh On

Page - 52 - of 89
Figure 29: Solid Mesh (Knee Model)
Resultant Data
Table 4: Resultant Force
Selection
set
Units Sum X
Sum Y Sum Z Resultant
Entire Model N -891.47 251.541 7.341 926.308

Page - 53 - of 89
Figure 30: Stress Analysis
The maximum stress the knee model can handle is equal to 2.19992e+006 N/m^2 and minimum
stress the knee model can handle is equal to 4.09813e-009 N/m^2.
Name Type Min Max
Strain1 ESTRN: Equivalent Strain 1.31581e-020
Element: 80351
9.88103e-006
Element: 86927
Name Type Min Max
Stress1 VON: von Mises Stress 4.09813e-009 N/m^2
Node: 132576
2.19992e+006 N/m^2
Node: 144447
Assem-1237654_KneeModel_Ah1-Static 1-Stress-Stress1

Page - 54 - of 89
Name Type Min Max
Assem-1237654_KneeModel
Figure 31: Strain Analysis
The maximum stress the knee model can handle is equal to 9.88103e-006 N/m^2 and minimum
stress the knee model can handle is equal to 1.31581e-020 N/m^2.
Factor of Safety:
The factor of safety is the factor of ignorance. If the stress on one part at a critical location is
known precisely i.e. applied stress (Sapp), and the material’s strength i.e. allowable stress is
known with precision and the allowable stress (Sallow) is greater than applied stress, then that
part will not fail. However, in real world all the aspects of design have some degree of
uncertainty and therefore factor of safety is needed. In practical, factor of safety is used in one
of three ways: (a) it can be used to reduce allowable strength such as yield strength of material
to a lower level of comparison with applied strength, (b) it can be used to increase the applied

Page - 55 - of 89
stress for comparison with allowable stress, (c) it can be used as a comparison for the ratio of
allowable stress to applied stress.
𝐹𝑎𝑐𝑡𝑜𝑟 𝑜𝑓 𝑆𝑎𝑓𝑒𝑡𝑦, 𝐹𝑆 =
𝑆 𝑎𝑙𝑙𝑜𝑤𝑒𝑑
𝑆 𝑎𝑝𝑝𝑙𝑖𝑒𝑑
𝑆 𝑎𝑙𝑙𝑜𝑤𝑒𝑑 = 8.2𝑒 + 008 𝑁/𝑚2
= Maximum stress
𝑆 𝑎𝑝𝑝𝑙𝑖𝑒𝑑 = 6.2𝑒 + 008 𝑁/𝑚2
= Material Yield Strength
𝐹𝑆 =
8.2𝑒 + 008
6.2𝑒 + 008
= 1.3
Figure 32: Factor of Safety

Page - 56 - of 89
4.3 Motion Analysis
4.3.1 Description of our Problem statement
Our problem describes the mechanism of a human leg (knee). So therefore, we plot our study
around knee mechanism" reacting forces and moment".
Assumptions:
We start our study by assuming that the human want sitting and his knee perpendicular to his leg.
Figure 33: Human (knee) Position while sitting

Page - 57 - of 89
Figure 34: Face 1 and Face 2 are perpendicular to each other
Considering the assumption of sitting, the below knee (tibia) and the above knee (femur or
thigh) are perpendicular to each other.
Then we assume that the knee rotates with limited angle between 0 to 90 degree, so we added
a virtual motor to make this rotation.
Figure 35: Virtual position of motor
And we added force 412N on thigh perpendicular to knee with a distance equal to 868 mm.

Page - 58 - of 89
Figure 36: Moment analysis around knee
Figure 37(a): Leg (femur & tibia) Figure 37(b): Knee Joint
Figure 37(c): Knee bonded with thigh acting as Human Femur
Modeling Information:
We simplify our problem by neglecting weight of modeling parts and concentrate all weight at
force 412N.
Units have been kept in SI (MKS) system and the material properties have been excluded.

Page - 59 - of 89
Figure 38: Units of the measurement
Graphs 1: Torque vs Time
Graph no.1 plot the relation between torque and time, since our calculation duration was 5
second, we found that the maximum torque came at the converting from inertia state to dynamic
state.
Max. Torque at force equal to 412 N = 352878 N.mm

Page - 60 - of 89
Graphs 2: Torque and Angular Displacement vs Time
Graph no.2 plot the relation between torque and angular displacement. We found that max.
torque achieved at angle equal zero (inertia state).
We check our calculation by calculate the error percentage.
Since;
𝑃𝑒𝑟𝑐𝑒𝑛𝑡 𝑒𝑟𝑟𝑜𝑟 =
|𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑 − 𝐴𝑐𝑡𝑢𝑎𝑙|
𝐴𝑐𝑡𝑢𝑎𝑙
𝑋 100%
Theortical "actual": torque= force *distance*cos.angle
Where force =412N, Distance =868mm, Angle=zero.
We used cos. and not sin. because we take the horizontal axis our datum axis
Therefore; Torque theoretical = 412*868*1
Torque theoretical = 357616 N.mm & Torque measured = 352878 N.mm
Therefore; error percentage = 1.32%
This is an accepted error because error is smaller than 10%
Also, we used 25 frame per second (means calculation repeating 25 time every 1 sec.), we can
use more frames per second to get more accurate result, if the result wasn't accepted.

Page - 61 - of 89
Graph 3: Torque vs Angle of Rotations (Various angles at 0, 30, 60,90 degrees)
Standing position represents the angle of zero degree. From the graph, we can see that the
maximum torque was obtained there. As the motion reaches towards sitting position, i.e. the
angle of rotation keeps on increasing, the value of torque decreases.

Page - 62 - of 89
CHAPTER 5: CONCLUSIONS
The static structural analysis of the knee joint has a great significance, as these analytical results
provide us a wider knowledge about the mechanical behavior of the knee. Performing stress
analysis as a simulation method instead of intrusive methods is one of the important part of
biomechanical study for different 3D models. The study reveals that the stress analysis work
performed will help us to obtain a rough geometry of the knee joint. The stress and motion
analysis has been done on the designed human knee model. From the analysis, several
conclusions are made which are listed below.
Table 5: Stress Analysis comparison with Knee model and Biological Knee Implant
Stress
Strain
Load
Resultant force
Material
Safety Factor
Knee Model
2.19992e+006 N/m2
9.88104e-009 N/m2
926.308 N
Biological Knee Implant
3.52e+005 to 5.62e+007 MPa
Alloy Steel
412 N 686.7 N
1.3 5.05

Page - 63 - of 89
Figure 39: Distribution of Stress on Knee Model
From the figure, we can see that the stress and tension has been evenly distributed in the femoral
(above knee component) and tibial (below knee component). The above figure shows in more
details the distribution of stress and displacements in the prosthetic knee model, therefore it
can be analyzed the greater stresses are generated in this component and even its distribution
is uniform, it has higher values toward the center of the element, due to the weight of the tibial
component and the loads applied in this.
The motion study allows observing the approximate behavior that the ligaments have after a
knee replacement. The mechanical behavior of medial collateral ligament is simulated through
linear springs (spring stiffness=0.024 Nm/Kg deg). It is considered that in the finite element
study (FES), the joint had a hinge type behavior, in which the tibia and corresponding
component remained fixed on the environment, whereas the femur presented the rotation of the
structure, contrary to the motion analysis. The analysis was developed with a 0° flexion with
an equivalent distributed load of 84 kg (412Nx2) in the perpendicular direction of the femoral

Page - 64 - of 89
component. Figure below shows the applied load along with weight of the human body on the
knee model.
Figure 40: Applied and Distributed Load on Knee Model
Table 6: Motion Analysis Data for Knee model
Future Work:
The future work will be modelling the knee model design into a 3-D model and apply the
motion analysis data. And finally develop the prototype of the affordable knee design.
REFERENCES
Mass
Min Mass
Max Mass
Leg Length
Torque
Angular Velocity
Power generated
Spring stiffness
Material
Pressure
Alloy Steel
2.25 Mpa
200x103
Nmm
53 RPM
1256 watts
352878 Nmm
30 RPM/3.142 rad/sec
1117.93 watts
0.024 Nm/Kg-deg
Knee Model Seimen/BIOM Foot
85 Kg
71 Kg
112 Kg
868 mm

Page - 65 - of 89
1) Martin Kub´ıˇcek, Zdenˇek Florian, Stress Strain Analysis of Knee Joint
2) Benjamin Low, ‘Design of A 3 Axis Wear Testing Device to Evaluate the Effect
of Slide to Roll Ratio on Ultra High Molecular Weight Polyethylene Wear in Total Knee
Replacements.
3) Roozbeh Borjian, ‘Design, Modelling, and Control of an active Prosthetic Knee.’
4) Jin D, Zhang R, Dimo HO, Wang R, Zhang J. ’Kinematic and dynamic performance of
prosthetic knee joint using six-bar mechanism. 2003 Jan-Feb;40(1):39-48.
5) Dr. Grant McGimpsey and Terry C. Bradford. ‘Limb Prosthetics Services and Devices.
Critical Unmet Need: Market Analysis’
6) Modan M, Peles E, Halkin H, Nitzan H, Azaria M, Gitel S, Dolfin D, Modan B. (1998).
Increased cardiovascular disease mortality rates in traumatic lower limb amputees. Am J
Cardiol. 82 (10), 1242-1247.
7) Argunsah, H., Davis, B.L. Application of Biomimetics in the Design of Medical Devices.
In: Bar-Cohen, J. (eds.) Biomimetics Nature-Based Innovation. 1st ed. Florida, USA:
CRC Press; 2012. p. 445-460
8) Hande Argunsah Bayram. ‘Biomechanics of Prosthetic Knee Systems: Role of Dampening
and Energy Storage Systems’, 2013. Cleveland State University
9) Van der Bogert, “Prosthesis Design and Control’.
15) http://www.aofas.org/footcaremd/treatments/Pages/Below-Knee-Amputation.aspx
16) http://www.amputee-coalition.org/resources/the-prosthetic-knee/
17) Össur. Rheo knee. http://www.Össur.com/pageid=12702 (accessed 23 September 2011).
18) https://professionals.ottobockus.com/Prosthetics/Lower-Limb-Prosthetics/Knees-
Mechanical/Single-Axis-Knee-Joint-Break/p/3R15

Page - 66 - of 89
19) Winter, D.; “Biomechanics and motor control of human movement,” 3rd ed., John Wiley
& Sons Inc., 2005.
20) (2008) Otto Bock Healthcare [Online]. Available: http://www.ottobock.com
21) Aeyels, B.; Peeraer, L.; Vander Sloten, P.; Van der Perre, G.; “Development of an above-
knee prosthesis equipped with a microcomputer controlled knee joint: First test results,”
Journal of Biomedical Engineering, vol. 14, pp. 199–202, May 1992.
22) Zlatnik, D.; Steiner, B.; Schweitzer, G.; “Finite-State Control of a Trans-Femoral (TF)
Prosthesis,” IEEE Transaction on Control Systems Technology, vol. 10, no. 3, pp. 408-420,
May 2002.
23) Carlson, J.D.; Matthis, W.; Toscan, J.R.; “Smart prosthetics based on magnetorheological
fluids,” Proceedings of SPIE‟01: The International Society for Optical Engineering, vol.
4332, pp. 308-316, 2001.
24) Kim, C.; Lee, J.; Xu, X.; “Design of biped robot with heterogeneous legs for advanced
prosthetic knee application,” SICE-ICASE International Joint Conference, pp. 1852-1855,
2006.
25) Sup, F.; Bohara, A.; Goldfarb, M.; “Designed and Control of a Powered Transfemoral
Prosthesis,” The International Journal of Robotics Research, vol. 27, no. 2, pp. 263-273, Feb.
2008.
[26] Cairo, A.; “Orthopaedic Project in Afghanistan”, The International Committee of the
Red Cross (ICRC) Geneva, Fact Sheet, 2005.
[27] Machel, G.; “Impact of armed conflict on children- Land-mines: A deadly inheritance,”
United Nations Department for Policy Coordination and Sustainable Development (DPCSD)
and UNICEF, 1996.
[27] Lim, J.; “The Mechanical Design and Analysis of an Active Prosthetic Knee,” Master of
Applied Science thesis, University of Waterloo, Ontario, Canada, May 2008.

Page - 67 - of 89
[28] (2008) Human Anatomy Online website. [Online]. Available:
http://www.innerbody.com/htm/body.html
[29] http://training.seer.cancer.gov/module_anatomy/unit1_3_terminology2_planes.html
[30] Rose, J.; Gamble, J.G.; “Human Walking,” 3rd ed., Philadelphia: Lippincott Williams &
Wilkins, 2005.
[31] (2008) [Online]. Available: http://www.univie.ac.at/cga/history/modern.html
[32] Winter, D.; “Biomechanics and motor control of human movement,” 3rd ed., John Wiley
& Sons Inc., 2005.
[33] (2008) Otto Bock Healthcare [Online]. Available: http://www.ottobock.com
[34] Peizer, E.; Wright, D. W.; “Human Locomotion,” 1969.
[35] Zlatnik, D.; Steiner, B.; Schweitzer, G.; “Finite-State Control of a Trans-Femoral (TF)
Prosthesis,” IEEE Transaction on Control Systems Technology, vol. 10, no. 3, pp. 408-420,
May 2002.
[36] Carlson, J.D.; Matthis, W.; Toscan, J.R.; “Smart prosthetics based on
magnetorheological fluids,” Proceedings of SPIE‟01: The International Society for Optical
Engineering, vol. 4332, pp. 308-316, 2001.
[37] Kim, C.; Lee, J.; Xu, X.; “Design of biped robot with heterogeneous legs for advanced
prosthetic knee application,” SICE-ICASE International Joint Conference, pp. 1852-1855,
2006.
[38] Flowers, W. C.; Mann, R. W.; “Electro-hydraulic knee-torque controller for a prosthesis
simulator,” ASME Journal of Biomechanical Engineering, vol. 99, no.4, pp. 3–8, 1977.
[39] Barton´ıˇcek J., Heˇrt J.: Základy klinické anatomie pohybového aparátu, Maxdorf,
Praha 2004, 256 pages
[40] Boudech Z., Horký D., Janeˇcek M.: Chrupavka a synoviáln´ı tkáˇn lidského kloubu,
Masarykova universita v Brnˇe, Brno 1990, 150 pages

Page - 68 - of 89
[41] ˇCihák R.: Anatomie 1, Avicentrum, Praha 1987, 546 pages
[42] Dungl P.: Ortopedie, Grada Publishing 2005, 1280 pages
[43] Hlavoˇn, P., Florian, Z., Fuis, V., Návrat, T., Jan´ıˇcek P.: Stress-deformation analysis of
an elbow articulation with radial head replacement, World Congress on Medical Physics and
Biomedical Engineering 2006, Seoul, South Korea
[44] Jan´ıˇcek P: Systémové pojet´ı vybraných obor˚u po techniky – Hledán´ı souvislost´ı,
Part I, CERM, Brno 2007, 682 pages
[45] Janura M.: Úvod do biomechaniky pohybového systému ˇclovˇeka, Univerzita
Palackého v Olomouci, Olomouc 2003, 85 pages
[46] Ko R., Takigawa M.: The tension test upon the costal cartilage of human body, J. Kyoto
Pref. Med Univ. 53, 1953
[47] Kˇren J., Rosenberg J., Jan´ıˇcek P.: Biomechanika, ZˇCU v Plzni, Plzeˇn 2001
[48] Lindahl O., Lindgren A.G., Cortical bone in man. II. Variation in tensile strength with age
and sex, Acta Orthop. Scand., 1967, 141 pages
[49] Morrison J.B.: Bioengineering analysis of force actions transmitted by the knee joint,
Biomedical Engineering 3, 1968
[50] Návrat T., Fuis V., Hlavoˇn P., Jan´ıˇcek P.: Strain – Stress Analysis of Artificial Hip
Joint, Influence of Bearing Material on Contact Pressure, World Congress on Medical Physics
and Biomedical Engineering, Seoul 2006, p. 2822–2825
[51] Valenta J., Konviˇcková S.: Biomechanika ˇclovˇeka – svalovˇe kostern´ı systém II, ˇ
CVUT, Praha 1997, 175 pages
[52] Vaverka F., Základy biomechaniky pohybového systému ˇclovˇeka, Univerzita
Palackého, Olomouc 1997
[53] Yamada H.: Strength of Biological materiale, The Wiliams & Wilkins Company,
Baltimore 1970

Page - 69 - of 89
[54] Jharana Deoriya, ‘Stress Analysis of Knee Joint And Knee Prosthesis’, Department of
Biotechnology & Medical Engineering National Institute of Technology Rourkela-769008,
Odisha, India
[55] Daniel Rodrigo Castillo Brito, Olga Lucia Ramos Sandoval and Dario Amaya Hurtado,
‘Mechanical Analysis Of The Prosthetic Knee In Flexion’, ARPN Journal of Engineering and
Applied Sciences, VOL. 11, NO. 4, FEBRUARY 2016

Page LXX of 89
APPENDICES
Appendix 1: Designing Knee Joint Parts Using SolidWorks

74 | P a g e
A) Appendix 2: Assemble of all the Parts Using SolidWorks

77 | P a g e
Final Assembly of Knee Joint Model

78 | P a g e
Appendix 3: Stress Analysis
Simulation of
KneeModel
Date: Wednesday, November 23, 2016
Designer: Solidworks
Study name: Static 1
Analysis type: Static
Table of Contents
Description ..........................................78
Assumptions .........................................79
Model Information..........Error! Bookmark not
defined.
Study Properties ....................................80
Units ..................................................80
Material Properties.................................81
Loads and Fixtures .................................82
Connector Definitions..............................83
Contact Information ...............................83
Mesh information ...................................84
Sensor Details .......................................88
Resultant Forces....................................88
Beams.................................................88
Study Results .... Error! Bookmark not defined.
Conclusion ....... Error! Bookmark not defined.
Description
No Data

79 | P a g e
Assumptions
Original Model
Model Analyzed

80 | P a g e
Study Properties
Study name Static 1
Analysis type Static
Thermal Effect: On
Thermal option Include temperature loads
Zero strain temperature 298 Kelvin
Include fluid pressure effects from
SOLIDWORKS Flow Simulation
Off
Solver type FFEPlus
Inplane Effect: Off
Soft Spring: Off
Inertial Relief: Off
Incompatible bonding options Automatic
Large displacement Off
Compute free body forces On
Friction Off
Use Adaptive Method: Off
Result folder SOLIDWORKS document
(C:UserssggauDesktopSolidoworks -
Practise)
Units
Unit system: SI (MKS)
Length/Displacement mm
Temperature Kelvin
Angular velocity Rad/sec
Pressure/Stress N/m^2

81 | P a g e
Material Properties
Model Reference Properties Components
Name: Alloy Steel
Model type: Linear Elastic
Isotropic
Default failure
criterion:
Max von Mises
Stress
Yield strength: 6.20422e+008
N/m^2
Tensile strength: 7.23826e+008
N/m^2
Elastic modulus: 2.1e+011 N/m^2
Poisson's ratio: 0.28
Mass density: 7700 kg/m^3
Shear modulus: 7.9e+010 N/m^2
Thermal expansion
coefficient:
1.3e-005 /Kelvin
SolidBody 1(Fillet1)(2-
1),
SolidBody 1(Boss-
Extrude2)(3-1),
SolidBody
1(Revolve2)(4-1),
SolidBody 1(Cut-
Extrude1)(5-2),
SolidBody 1(Kes-
Ekstrüzyon2)(6-1),
SolidBody 1(Cut-
Extrude3)(foot-1),
SolidBody 1(Boss-
Extrude1)(rood-1)
Curve Data:N/A

82 | P a g e
Loads and Fixtures
Load name Load Image Load Details
Force-1
Entities: 7 face(s)
Type: Apply normal force
Value: 412 N
Fixture name Fixture Image Fixture Details
Fixed-1
Entities: 4 face(s)
Type: Fixed Geometry
Resultant Forces
Components X Y Z Resultant
Reaction force(N) -891.47 251.541 7.341 926.308
Reaction Moment(N.m) 0 0 0 0

83 | P a g e
Connector Definitions
Connector Name Connector Details Connector Image
Spring Connector-1
Entities: 2 vertex(s)
Type: Spring(Two
locations)(Compr
ession &
Extension)
Axial stiffness value: 0.024 N/m
Tangential Stiffness: 0.024 N/m
Rotational stiffness
value:
0 N.m/rad
Pre-compression
value:
2.2e+006 N
Spring Connector-1
Contact Information
Contact Contact Image Contact Properties
Global Contact
Type: Bonded
Components: 1
component(s)
Options: Compatible
mesh

84 | P a g e
Mesh information
Mesher Used: Curvature-based mesh
Jacobian points 4 Points
Maximum element size 12.9024 mm
Minimum element size 0.645118 mm
Mesh Quality High
Remesh failed parts with incompatible mesh On
Mesh information - Details

85 | P a g e
Mesh Control Information:
Mesh Control Name Mesh Control Image Mesh Control Details
Control-1
Entities: 1 component(s)
Units: mm
Size: 6.45123
Ratio: 1.5
Total Nodes 149115
Total Elements 92224
Maximum Aspect Ratio 43.566
% of elements with Aspect Ratio < 3 98.4
% of elements with Aspect Ratio > 10 0.0813
% of distorted elements(Jacobian) 0
Time to complete mesh(hh;mm;ss): 00:00:09
Computer name:

86 | P a g e
Control-2
Units: mm
Size: 6.45123
Ratio: 1.5
Control-3
Units: mm
Size: 6.45123
Ratio: 1.5
Control-4
Units: mm
Size: 6.45123
Ratio: 1.5
Control-5
Units: mm
Size: 6.45123
Ratio: 1.5

87 | P a g e
Control-6
Units: mm
Size: 6.45123
Ratio: 1.5
Control-7
Units: mm
Size: 6.45123
Ratio: 1.5
Control-8
Units: mm
Size: 5.99078
Ratio: 1.5
Control-9
Units: mm
Size: 5.99078
Ratio: 1.5

88 | P a g e
Sensor Details
No Data
Resultant Forces
Reaction forces
Selection set Units Sum X Sum Y Sum Z Resultant
Entire Model N -891.47 251.541 7.341 926.308
Reaction Moments
Selection set Units Sum X Sum Y Sum Z Resultant
Entire Model N.m 0 0 0 0
Beams
No Data

89 | P a g e
Appendix 4: Motion Analysis

Design and Analysis of Affordable Artificial Knee Joint Model. Motion and Stress Analysis will be done on a digital model using SolidWorks

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (10)

Similar to Design and Analysis of Affordable Artificial Knee Joint Model. Motion and Stress Analysis will be done on a digital model using SolidWorks

Similar to Design and Analysis of Affordable Artificial Knee Joint Model. Motion and Stress Analysis will be done on a digital model using SolidWorks (20)

More from Gautam Singh

More from Gautam Singh (9)

Recently uploaded

Recently uploaded (20)

Design and Analysis of Affordable Artificial Knee Joint Model. Motion and Stress Analysis will be done on a digital model using SolidWorks