Biomechanical responses of normal and delipidized articular cartilage subjected to varying rates of loading.
In alignment with the proposition that a lipid layer overlays the superficial zone of the articular cartilage, this study presents the consequence of the removal of lipids on the load-bearing characteristics of the tissue. Both normal unmodified and delipidized cartilage matrices were loaded at four different strain-rates of 1.3 x 10(-4)/s, 1.3 x 10(-3)/s, 1.3 x 10(-2)/s, and 1.3 x 10(-1)/s to strains of no more than 40%, to compare their stress-strain and stiffness-strain-rate characteristics. Our results demonstrate that at the lowest strain-rate of 1.3 x 10(-4)/s, the stiffness of the delipidized matrix was lower in comparison to that of the normal unmodified tissue. This response was reversed at higher strain-rates of 1.3 x 10(-2)/s and above. We conclude, therefore, that in general, at physiological rates of loading, the depletion of lipids from the articular cartilage reduces its compliance by at least 25%. We infer from the present study that this degenerative stiffening is an important contributing factor in impairing the tissue's load processing function in osteoarthritic joints.
Oloyede
A
A
School of Mechanical, Manufacturing & Medical Engineering, Queensland University of Technology, Brisbane, Australia. k.oloyede@qut.edu.au
Gudimetla
P
P
Crawford
R
R
Hills
B A
BA
D000818:Animals; D002358:Cartilage, Articular / Q000502:physiology*; D002417:Cattle; D004548:Elasticity; D008055:Lipids / Q000502:physiology*; D011312:Pressure; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology*
D008055:Lipids