“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
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