Osteoarthritis is a chronic degenerative bone and joint disease of the elderly, characterized by degenerative changes in the articular cartilage with meniscal and synovial lesions as the main pathological changes. The exact cause of osteoarthritis remains unclear. It is thought to be related to age, mechanical wear and tear, and impingement factors, and has been found to be related to immune response, free radicals, increased intraosseous pressure, and cytokines, which are still under further investigation. Age is an important factor in osteoarthritis because degeneration of articular cartilage will be inevitable with age, as the water content decreases, viscoelasticity decreases, and resistance to impact and wear decreases. Most scholars now believe that although articular cartilage is more resistant to wear and tear, it is less resistant to impact. The physiological degeneration of articular cartilage is only a potential trigger for the development of osteoarthritis, not a determining factor. Articular cartilage damage is proportional to age and amount of exercise, and the older the age and the more cumulative damage, the more severe the degeneration of articular cartilage. After cartilage injury, the resistance to mechanical, cumulative, and repeated small impacts decreases, which can aggravate the degeneration of articular cartilage and lead to surface or deep cartilage damage, thus forming a vicious circle to further aggravate the injury. The degeneration of articular cartilage not only causes changes in its own biological and mechanical properties, but also inevitably affects the subchondral bone. The subchondral bone tissue is subjected to high compressive stress conduction and microfractures occur, followed by trabecular necrosis and cystic degeneration of the bone. During the process of bone tissue repair and remodeling, subchondral bone will form bone redundancy when repairing its own damage and cartilage defects. The destruction of cartilage and bone can in turn form microscopic free bodies in the joint, which can stimulate inflammation of the synovium.