Back pain is pain felt in the back. Episodes of back pain may be acute, sub-acute, or chronic depending on the duration. The pain may be characterized as a dull ache, shooting or piercing pain, or a burning sensation. The pain may radiate into the arms and hands as well as the legs or feet, and may include tingling, weakness or numbness in the legs and arms. The most common area of pain is the lower back, or lumbar area.The pain may originate from the muscles, nerves, bones, joints or other structures in the spine. Internal structures such as the gallbladder and pancreas may also refer pain to the back.Although back pain is common, it is rare for it to be permanently disabling. In most cases of disc herniations and stenosis, rest, injections or surgery have similar outcomes of general pain resolution after one year. In the United States, acute low back pain (also called lumbago) is the fifth most common reason for physician visits. About nine out of ten adults experience back pain at some point in their life, and five out of ten working adults have back pain every year. Low back pain causes 40% of missed days of work in the United States. Additionally, it is the single leading cause of disability worldwide.