Human body is the most perfect masterpiece of nature, the knee joint inside the human body has a delicate ultrathin layer of osteochondral interface between SOFT cartilage and HARD subchondral bone. In this interface, the sophisticated structures and excellent force transfer properties allow the knee to resist fatigue damage over a lifetime of loading cycles. The breakdown of the osteochondral interface commonly induces osteoarthritis (OA). Articular cartilage (AC) destruction and subchondral bone remodeling have been extensively studied in OA. While little is known about the changes in their connecting layer-osteochondral interface tissues during OA development. Thus, using multiple micro-nano analytical technologies, we investigated the physical and pathological calcification processes and mechanisms of the osteochondral interface in normal and OA tissues and explored their contribution to OA development.