Articular cartilage is a connective tissue covering the ends of long bones and allowing for normal joint motion. Degeneration of the articular cartilage occurs in osteoarthritis (OA) and is difficult to diagnose early. Treatment of degeneration or OA in cartilage typically involves implanted and surrounding materials that need to heal. It would be useful clinically to assess cartilage degeneration and healing. Indentation testing is a good candidate since it allows for non-destructive, rapid, and quantitative assessment of cartilage function. This dissertation aims to further the understanding and clinical utility of rapid indentation testing by investigating its biomechanies, efficacy, and novel use in human and animal articular cartilage.

Biomechanically, two-dimensional intra-tissue strain analysis indicated that strain magnitude increased with indentation depth, and suggested that the range of these strain magnitudes may have biological consequences. Indentation stiffhess was sensitive to mild cartilage degeneration near the surface. Correlative analyses suggested that structural integrity was the dominant effector of indentation stiffness. Sensitivity analysis further indicated high sensitivity of indentation testing to cartilage degeneration. Biologically, when cartilage was indented to increasing depths, increasing percentage of chondrocytes near the articular surface died, and the regions of cell death corresponded with regions of high strain concentration. Thus, indentation to a small depth would be advisable to avoid injury during indentation testing. Indentation testing was sensitive to the presence of step-off edges and material interfaces that are found in certain surgical treatments. Thus, indentation testing may be useful for novel applications of tissue characterization prior to surgery and for assessment of integrative repair post-operatively.

These studies provided evidence for the clinical applicability of indentation testing to detect mild degeneration of cartilage and to assess tissues before and after surgical treatment strategies. In addition, these studies provide a basis for developing effective and sensitive indentation probes and protocols.