Pain Definition, Pain Classification Physiotherapy

Pain – Definition and Classification

The International Association of Study of Pain’s widely used definition describes pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”.


According to Pain Physiology

Clifford J Woolf suggests three classes of pain:

Nociceptive pain

Inflammatory pain

Pathological pain


Nociceptive pain is caused due to an injury to the body tissue, this includes damage to muscle or bone such as bruises, cuts, fractures, burns, cancer and surgery. Pain reduces once the injury heals

Pain that is caused by the presence of a painful stimulus on nociceptors is called nociceptive pain. Nociceptive pain in its acute form usually serves an important biological function as it warns the organism of impending danger and informs the organism of tissue damage or injury

Nociceptive pain may also be divided into visceral, deep somatic and superficial somatic pain.

Visceral pain is diffuse, difficult to locate, often referred to a distant structures . It may be accompanied by nausea and vomiting and may be described as sickening, deep, squeezing, and dull ache.

Deep somatic pain is initiated by stimulation of nociceptors in ligaments, tendons, bones, blood vessels, fascia and muscles, and is dull, aching, poorly -localised pain.

Superficial pain is initiated by activation of nociceptors in the skin or other superficial tissue, and is sharp, well-defined and clearly located.


Neuropathic pain is caused due to dysfunction or damage to the nerves, spinal cord or brain. It is characterised by a burning, pins and needles, electrical, tingling or stabbing sensation. Pain can last for a long period of time, even after the injury has healed.


It is a pain experienced in response to a normally painless stimulus. It has no biological function and is classified by stimuli into dynamic mechanical, punctate and static. In osteoarthritis, NGF has been identified as being involved in allodynia.


Phantom pain sensations are described as perceptions that an individual experiences relating to a limb or an organ that is not physically part of the body. Limb loss is a result of either removal by amputation or congenital limb deficiency.

Phantom limb sensations can also occur following nerve avulsion or spinal cord injury.


Psychogenic pain is caused by psychological factors. Pain usually occurs due to tissue or nerve damage, but increases and is prolonged because of stress, fear, anxiety or depression

Psychogenic pain, also called psychalgia or somatoform pain, is pain caused, increased, or prolonged by mental, emotional, or behavioral factors. Headache, back pain, and stomach pain are sometimes diagnosed as psychogenic.


Breakthrough pain is transitory pain that comes on suddenly and is not alleviated by the patient’s regular pain management. It is common in cancer patients who often have background pain that is generally well-controlled by medications, but who also sometimes experience bouts of severe pain that from time to time “breaks through” the medication.

According to the Intensity

Pain Intensity can be broadly categorized as mild, moderate and severe. It is common to use a numeric scale to rate pain intensity where 0 = no pain and 10 is the worst pain imaginable:


Moderate: 5/10 to 6/10

Severe: >7/10

According to the Time course (Pain duration)

Acute pain

Pain of less than 3 to 6 months duration

Chronic pain

Pain lasting for more than 3-6 months, or persisting beyond the course of an acute disease or after tissue healing is finished .

Acute-on-chronic pain

Acute pain flare superimposed on underlying chronic pain


Alder Hey Triage Pain Score

Behavioral Pain Scale (BPS)

Brief Pain Inventory (BPI)

Checklist of Nonverbal Pain Indicators (CNPI)

Clinical Global Impression (CGI)

Critical-Care Pain Observation Tool (CPOT)


Dallas Pain Questionnaire

Descriptor differential scale (DDS)

Dolorimeter Pain Index (DPI)

Edmonton Symptom Assessment System

Faces Pain Scale – Revised (FPS-R)

Face Legs Activity Cry Consolability scale

Lequesne algofunctional index

McGill Pain Questionnaire (MPQ)

Neck Pain and Disability Scale –(NPAD)

Numeric Rating Scale (NRS-11)

Oswestry Disability Index

Palliative Care Outcome Scale (PCOS)

Roland-Morris Back Pain Questionnaire

Support Team Assessment Schedule (STAS)

Wong-Baker FACES Pain Rating Scale

Visual analog scale (VAS)

Multiple Pain Rating Scales

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