Osteoarthritis (OA) . OA is the wear-and-tear arthritis that usually occurs with aging or after injury. With OA, there's a wearing down of the cartilage that cushions the ends of the bones. OA causes joint swelling in those joints that bear weight over a lifetime, such as knees, hips, feet, and spine.
During the Zhou dynasty, the Chinese developed irrigation and flood- control systems. As a result, farmers could grow more crops than ever before. Because more food could support more people, the population increased. During the late Zhou dynasty, China's population had expanded to about 50 million people. Zhou people also learned to use iron, which was cheaper and stronger than bronze. Iron weapons, the catapult and China's first cavalry (military on horseback) were some of the Zhou achievements that helped strengthen the army.
The Song dynasty (Chinese: å®æ; 960â1279 CE) provided some of the most significant technological advances in Chinese history, many of which came from talented statesmen drafted by the government through imperial examinations. The ingenuity of advanced mechanical engineering had a long tradition in China. The Song engineer Su Song admitted that he and his contemporaries were building upon the achievements of the ancients such as Zhang Heng (78â139), an astronomer, inventor, and early master of mechanical gears.