Acute pain can be a normal reaction to an injury, surgery or certain medical conditions such as infection or inflammation. Chronic pain is different. It may have started with an injury or illness, but chronic pain can also be the result of an ongoing disease such as cancer or arthritis. It can even start without a known cause or obvious injury. The American Chronic Pain Association defines chronic pain as pain that continues a month or longer after normal recovery time for an injury or illness, or pain that continues for months or years as a result of a chronic condition.
Some of the most common areas for chronic pain are back, neck, head and peripheral nerves.