This is a response that is complex from trauma to tissue during a surgery which then stimulates central nervous system hypersensitivity. This results in pain in other areas than those that were affected directly from the surgical procedure. The pain can be experienced either outpatient or inpatient. Pain can be brought on by surgical procedures that are minor such as a dental procedure or major operations such as a triple-bypass surgery of the heart.
Post-Surgical Pain Joseph Smith, PhD