In osteoarthritis (OA), a disabling and painful disease, articular cartilage is unable to perform its function of resisting loads and providing joint lubrication. The cause of OA remains unknown, as is the exact progression from early biochemical changes to the complete loss of cartilage. The extracellular matrix of articular cartilage is made up of a complex arrangement of water-imbibing glycosaminoglycans (GAG) that are held together by a tensioned network of collagen fibres. Some research evidence suggests that osteoarthritic changes commence at the articular surface, and are followed by a larger scale disruption of the extracellular matrix. An in vivo test of cartilage surface integrity could be an early and sensitive test for diagnosis and for monitoring the pathogenesis of OA. The objective of this thesis was to investigate the three-dimensional architecture of articular cartilage using novel imaging techniques and apply these techniques to a model of early osteoarthritis. Several key findings are presented. To better understand the collagen component in OA, tendon was studied on MRI, as it is relatively homogeneous. While studying the large scale influences of collagen orientation on the MRI parameter T2, it was revealed that MRI has sufficient resolving power to detect microscopic changes in collagen orientation (collagen crimp). Healthy articular cartilage was then used to develop specific imaging and microscopy techniques to assess and monitor the structure of the articular surface. Finally, T2 mapping and polarized light microscopy were applied to an animal model of early osteoarthritis, where they revealed notable changes in collagen organization at the articular surface in diseased samples.
These studies contribute to the current understanding of articular cartilage structure in health and disease, and support the hypothesis that disruption of the articular surface is one of the initiating factors in osteoarthritis.