“Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of damage. and we can say that pain is always a subjective sensation and is always unpleasant”.

Pain is not necessarily associated with ongoing tissue damage, it is a subjective experience and has an emotional as well as a sensory component.

As a doctor we can say that Pain is our friend, as it is the main reason for a patient to come to a doctor, according to stats out of all the patients who come to a doctor 90% of the patients visit a doctor due to pain.

Pain is very difficult to describe inspite of many efforts to establish ways to classify and describe it in a brief manner.

Pain is multi factorial and to control pain we have to eliminate the cause of pain, for instant relief we can use drugs but as pain is the surface symptom of an underlying disease we have to eliminate the cause of pain to relieve the patient permanently.


Pain cannot be classified under a particular aetiology and pathogenesis as aetiology and pathogenesis of pain is multifactorial. So pain is classified according to

  • Aetiology and pathogenesis.
  • Duration.
  • Site.

Aetiology and pathogenesis:

  1. Here the pain is classified according to the cause and the pathogenesis of the disease:
  2. Physiological: An acute response to an injury.
  3. Inflammatory: When pain is generated and maintained mainly by inflamatory mediators.
  4. Cancer related pain: Aetiology is usually multifactorial. It may be predominantly physiological, inflammatory, neuropathic or ischaemic, or combination of the above.
  5. Neuropathic: Pain arising from injury or dysfunction of the central or peripheral nervous system.
  6. Central: Pain caused by a lesion or or dysfunction of the central nervous system. It can affect brain or spinal cord, or both.
  7. Ischemic: It is mainly due to the decrease in blood supply to the organs, or the nerves that supply them.
  8. Psyhogenic: Pain especially chronic pain has both an emotional and a behavioural component, But a purely psychogenic pain is rare.


It is mainly divided into 2 types:

  1. Acute: It is mainly cause by response to an injury, it disappears with the withdrawal of the noxious stimulus, or when the injury is healed.
  2. Chronic: This is a more complicated version of pain as it is associated with a serious pathological condition, Pain is considered to be chronic when the pain persists for more than 3 months, the main reasons for chronic pain are malignancies or rheumatoid arthritis or any pathological condition which persists for longer duration. Chronic pain is associated with disability and a significant behavioural response.


  1. Somatic: It is usually localized pain, which is confined to a particular area.
  2. Visceral: Poorly localized, it is spread over a large area which cannot be precisely located.
  3. Referred: Pain which is felt at one site but the cause or aetiology of the pain is at some other site. For ex: during cardiac problem the pain is felt in the left arm in the upper part of abdomen etc.

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