Identification of important interactions between subchondral bone ...
Identification of important interactions between subchondral bone ...
Identification of important interactions between subchondral bone ...
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2.2 Biology <strong>of</strong> the joint<br />
CHAPTER 2: Introduction<br />
In order to get insight into the underlying processes <strong>of</strong> OA, it is <strong>important</strong> to understand the<br />
physiology and biology <strong>of</strong> healthy joints. Joints that are able to move freely are termed synovial<br />
joints and together with muscles and <strong>bone</strong> they represent the machinery that enables us to move.<br />
The knee is a synovial weight-bearing joint, which comprises many tissues that maintain the<br />
mobile function; articular cartilage, <strong>subchondral</strong> <strong>bone</strong>, ligaments, capsule, synovial membrane and<br />
supporting muscles (fig. 1A). The ends <strong>of</strong> the adjoining <strong>bone</strong>s are covered with articular cartilage,<br />
which functions as a shock-absorber and provides a friction-free surface that enables the <strong>bone</strong>s<br />
to move smoothly against each other. The joint capsule, tendons, muscles and ligaments provide<br />
stability <strong>of</strong> the joint. The <strong>bone</strong>s are connected by strong ligaments and the tendons provide the<br />
attachment <strong>of</strong> muscles to the <strong>bone</strong>. The inside <strong>of</strong> the joint is covered with a synovial membrane,<br />
which provides and holds the lubricating synovial fluid that enables the joint to move easily (see<br />
fig. 1B) 13,14 .<br />
Fig. 1. Illustration <strong>of</strong> a healthy synovial knee joint. The different components <strong>of</strong> a knee<br />
joint are outlined in figure A and B. A) The components responsible for stability and<br />
movement are shown. B) The components <strong>of</strong> the articular capsule, which provide an easy<br />
friction, are shown in details. The figure was produced by Madsen, S.H.<br />
2.2.1 Development <strong>of</strong> <strong>bone</strong> from a cartilage template<br />
Although OA is a disease <strong>of</strong> the whole joint, this thesis focuses on <strong>bone</strong> and cartilage, which are<br />
the most affected tissues in OA. A description <strong>of</strong> the development <strong>of</strong> the joint, with respect to<br />
<strong>bone</strong> and cartilage, will help the reader to understand the tight connections <strong>between</strong> these two<br />
tissues.<br />
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