Referred pain

From Freepedia

Referred pain is an unpleasant sensation localised to an area separate from the site of the causative injury or other painful stimulation. Often, referred pain arises when a nerve is compressed or damaged at or near its origin. In this circumstance, the sensation of pain will generally be felt in the territory that the nerve serves, even though the damage originates elsewhere.

A common example occurs in intervertebral disc herniation, in which a nerve root arising from the spinal cord is compressed by adjacent disc material. Although pain may arise from the damaged disc itself, pain will also be felt in the region served by the compressed nerve (for example, the thigh, knee, or foot). Relieving the pressure on the nerve root may ameliorate the referred pain, provided that permanent nerve damage has not occurred.

A similar mechanism may be responsible for some instances of the phantom limb syndrome in amputees.

Despite the proliferation of literature on the mechanisms of referred pain, it is a process that is still not well understood.