Cartilage Consolidation Under Load

Articular cartilage resists joint loads through a biphasic mechanism: an incompressible interstitial fluid phase that pressurizes under compression and briefly shields the solid collagen–proteoglycan matrix from stress, then slowly drains through the free articular surface while the matrix takes up more and more of the load. This simulator solves that fluid-pressure diffusion problem on a depth grid through a cylindrical cartilage explant under confined compression — the same test geometry used to measure real biphasic tissue properties — and tracks how falling proteoglycan content speeds fluid loss, raises solid-matrix stress, and accumulates fatigue damage at the free surface first, reproducing the surface-led fibrillation pattern seen in early osteoarthritis.