Sudden pain in the knee in the elderly is mostly caused by the growth and degeneration of the bones in the knee joint, resulting in osteoarthritis in the knee joint, narrowing of the joint space and friction in the cartilage when moving the joint, resulting in pain and swelling, accompanied by popping and ringing, or affecting the normal movement of the knee joint. The bones in the knee joint of the elderly are also prone to calcium loss and localized osteoporosis, which can also lead to a gradual decrease in the absorption of nutrients by the local muscles, resulting in pain and swelling of the knee. In terms of treatment, older people can be told to strengthen the knee joint regularly with proper rehabilitation exercises or to eat more calcium-rich foods in their diet, which can relieve the painful situation.