Time evolution of deformation in a human cartilage under cyclic loading

Area of Science:

• Biomechanics
• Biomaterials Science
• Orthopedics

Background:

• In vivo imaging reveals substantial contact deformations in human knee cartilage (10-30%) under physiological loads.
• Understanding these large, time-dependent deformations is critical for cartilage health and function.

Purpose of the Study:

• To develop a biphasic, large deformation, non-linear poroelastic model for human knee cartilage.
• To accurately represent the time-dependent and magnitude of cyclic cartilage deformations in vivo.

Main Methods:

• Developed a novel poroelastic model incorporating cartilage tension-compression nonlinearity.
• Included a constitutive relation where stiffness and permeability adjust with strain-dependent aggrecan concentration.
• Validated model predictions against experimental data from human osteochondral plugs.

Main Results:

• Optimized model parameters achieved an excellent fit with experimental data.
• The model successfully reproduced experimentally observed transient and steady-state cartilage deformations under cyclic loading.
• Steady-state deformations cycled between 10% (exudation strain) and 20% (total strain).

Conclusions:

• The developed large deformation poroelastic model accurately captures in vivo human knee cartilage behavior under cyclic loading.
• Model shows pore fluid exudation equals imbibement at steady-state cyclic loading, maintaining tissue fluid balance.
• This model provides a valuable tool for studying cartilage mechanics and potential therapeutic interventions.