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Viscoelastic Properties of Osteoarthritic Human Knee Articular Cartilage

The musculoskeletal system relies heavily on articular cartilage, which is a hydrated supportive tissue that covers diarthrodial joints. Most people over the age of 55 suffer from osteoarthritis, which is the most common degenerative joint disease. The mechanical flexibility, lubricating behaviour, damping function, and energy absorption and dissipation capacity of articular cartilage - all are affected due to the osteoarthritic disorder. The changes in biomechanical viscoelastic properties of knee articular cartilage due to progression of osteoarthritis were analysed. Static deformation was imposed on low grade and high-grade osteoarthritic articular cartilage. After imposing the constant compressive stress on articular surface of the cartilage section, the time dependent stress relaxation data were acquired from the degenerated osteoarthritic tissue. An empirical model - the generalized Maxwell model - was used to analyse the changes in viscoelastic properties of osteoarthritic cartilage. The viscoelastic properties such as stress relaxation time and elastic modulus parameters of low grade and high grade osteoarthritic articular cartilage were compared and observed to differ significantly. Moreover, the mean value of instantaneous and equilibrium modulus both were observed higher in the low grade of osteoarthritic cartilage. The present results obtained using the generalized Maxwell model demonstrated that the significant changes occur in viscoelastic stress relaxation properties of knee articular cartilage during the progression of osteoarthritis. Such changes might play a crucial role in the physiological stress distribution, pathogenesis of osteoarthritic disorder and thus can ultimately affect the biomechanics of the knee joint.