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					Influence of loading conditions on the structure and mechanical properties
                            of articular cartilage.

Daniel M Espino & Duncan ET Shepherd
School of Mechanical Engineering, University of Birmingham, Birmingham UK

The aim of this session is to discuss how loading conditions that a joint is exposed to
influence both the structure and mechanical properties of the underlying articular
cartilage. This is important as cartilage degeneration, as occurs during osteoarthritis,
involves changes to structure and properties.

Different joints across the body are exposed to different movements and, thus, loading.
For example, the loads and stresses experienced by the hip are different to those
experienced by the knee during walking or running. Different joints also experience
different rates of cartilage degeneration. The ankle, while exposed to higher stress
experiences little cartilage degeneration unlike the hip or knee. Variation in structure and
mechanical properties occur across different joints, within a joint and within a joint
component. The knee is a good example of this.

The medial and lateral components of the knee are exposed to different types of loading.
During walking, the lateral femoral condyle of the knee rotates unlike the more static
medial condyle. However, most compressive loads pass through the medial knee. The
patella, menisci and ligaments all affect loading distribution across the knee. Thus, the
knee joint is used as an example of how cartilage properties and structure vary within a
joint, and differences in the boundary conditions that cartilage is exposed to.

The session includes:
 background to the knee, its anatomy and biomechanics;
 discussion of the different loading conditions knee cartilage is exposed to in vivo;
 description of the differences in cartilage structure (including collagen orientation and
 detail of the mechanical properties typically measured (including different testing
    regimes) and how these vary across the knee.
Finally the question is asked, whether trends between cartilage boundary conditions and
structure/properties can be determined?

Experiments are currently taking place in our laboratory to answer this question. These
build on our previous knee mechanics and cartilage micro-structural studies.

ACKNOWLEDGEMENT: “This research was supported by a Marie Curie Intra European Fellowship within the 7th
European Community Framework Programme” (Programme number: FP7/2007-2013; under grant agreement n°252278).
Daniel is currently a Marie Curie Research Fellow at the University of Birmingham
(School of Mechanical Engineering). His research experience includes modelling,
mechanical testing and structural analysis of soft tissues (including heart valves,
intervertebral discs and articular cartilage).

In 2005 he obtained his PhD in Bio-Engineering at the University of Aberdeen.
Following his PhD, he was awarded a British Heart Foundation Junior Fellowship which
he also at Birmingham. He has since developed expertise on the musculo-skeletal system
internationally, as a Research Fellow at both the University of Auckland (New Zealand)
and the Istituto Ortopedico Rizzoli (Bologna, Italy).

Dr DET Shepherd
Duncan is a Senior Lecturer in Bio-medical Engineering. After gaining BEng
(Mechanical Engineering) and PhD (Bio-engineering) degrees he has developed research
interests in the design and testing of implantable medical devices over the last 13 years.
He is the author of around 50 peer-reviewed publications in engineering and medical
journals, and has been invited to give seminars in Canada, India, Malaysia and the UK.
He is a Chartered Engineer and a Fellow of the Institution of Mechanical Engineers. He
serves on the Engineering in Medicine and Health Division Board of the Institution of
Mechanical Engineers and is editor of their newsletter. He also serves on the editorial
boards of the Open Mechanical Engineering Journal, the Open Biomedical Engineering
Journal and the International Journal of Biomedical Engineering and Consumer Health

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