(See also Overview of Pain.)
Most pain is nociceptive pain. It results from stimulation of pain receptors for tissue injury (nociceptors), which are located mostly in the skin or in internal organs. The injury may be a cut, bruise, bone fracture, crush injury, burn, or anything that damages tissues.
Nociceptive pain is typically aching, sharp, or throbbing, but it may be dull. A blockage in an internal organ usually causes deep, cramping pain, and the pain's location may be hard to pinpoint. But when certain soft tissues, such as those that surround and enclose internal organs, are damaged, the pain may be sharp and easy to locate.
The pain almost universally experienced after surgery is nociceptive pain. The pain may be constant or intermittent, often worsening when a person moves, coughs, laughs, or breathes deeply or when the dressings over the surgical wound are changed.
Most of the pain due to cancer is nociceptive. When a tumor invades bones and organs, it may cause mild discomfort or severe, unrelenting pain. Some cancer treatments, such as surgery and radiation therapy, can also cause nociceptive pain.
Pain relievers (analgesics), including opioids, are usually effective.