Structural variations in cartilage make it sensitive to shifts in joint kinematics

• Main Author: Briant, Paul Leonard
• Format: Dissertation
• Language: English
• Subjects: engineering, mechanical
• ISBN: 0549353550; 9780549353553

The purpose of this dissertation is to evaluate the mechanical sensitivity of knee articular cartilage to altered joint kinematics during walking. Shifts in joint kinematics have been suggested to cause the premature osteoarthritis (OA) frequently developed in anterior cruciate ligament (ACL) injury patients. Such kinematic changes could initiate cartilage degeneration by shifting the location of frequent joint loading to regions of cartilage not conditioned to high load. To further evaluate this hypothesis, a series of studies was performed that analyzed the relationship between variations in cartilage structure, altered knee kinematics, and cartilage tissue mechanics.
Changes in knee kinematics during walking associated with ACL injury were shown to shift the regions of high stress in the medial tibial plateau towards the peripheral regions of the joint using a knee joint numerical model. This contact shift caused an overall increase in stress due to decreased joint conformity and was more pronounced in the medial compartment due to greater natural conformity. An experimental analysis of the cartilage matrix organization indicated significant variations in matrix structure between central and peripheral regions of tibial plateau cartilage, suggesting variations in tissue integrity and a conditioning of cartilage to its local mechanical environment. Finally, significant increases in continuum strain components associated with cartilage degeneration (tension and shear) were observed in the peripheral region, but not the central region, under the same increase in applied load. These experimental strain distribution measurements suggest regional variations in the mechanical response of cartilage to a change in applied load and that a shift in high load towards the periphery would result in substantial changes in internal strain leading to cartilage degeneration.
Taken together, the results of these studies provide a fundamental, mechanical basis for altered kinematics to initiate cartilage degeneration leading to OA. In addition, the insights provided by this work into the regional variations in cartilage structure and the translation of macroscopic loads to matrix deformations have direct implications on the development of clinical repair techniques such as osteochondral transplant surgery and cartilage tissue engineering.