Full domain surface distributions of micromechanical properties of articular cartilage structure obtained through indentation array

As a layered complicated porous elastic–plastic material, articular cartilages undertake the tasks of buffering stress, lubricating joint, and preventing wear. Nevertheless, the irregular articular cartilage shape indicates potential differences in properties at various regions. The lack of full domain surface micromechanical properties restricts the revelation of cartilage structure failure mechanism and impedes the design of biomimetic cartilage compatible with the actual working conditions. In the present work, the full domain knee articular cartilage surface was reasonably divided into microregions based on the approximate curvature principle. Through depth-sensing indentation array, the region-dependent differences in mechanical properties were revealed, and the hardness and Young's modulus distributions of full domain cartilage structure surface were experimentally obtained for the first time. The microstructure-property correlation was established and the microstructure-dependent load adaptability was also verified, as the region (concave side of condylar surface) with maximum hardness and Young's modulus exhibited a striped pattern with approximately consistent orientation, and the regions adjacent to the suprapatellar synovial bursa with lowest bearing capacity exhibited peeling collagen fibers.