General Principles of Pain

pain

“an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”

neurophysiology of pain

• Fully integrated experience of pain includes three components

  • Discriminative, affective, cognitive

• Patient's attitudes, beliefs, and personalities may strongly affect their experience of pain

• PT has moved away from biomedical paradigm that emphasizes tissue pathology and abnormality as a chief determinant of pain

• Moved toward a biopsychosocial approach because of health status and concurrent conditions that can influence the pain experience

  • Ex: psychological and intrinsic biological factors (genetics, age, and gender)

most to least sensitive tissues

• Periosteum

  • Outside the bone - this is what creates the pain when you break a bone

• Joint capsule

• Subchondral bone

  • Bone just underneath the layer of cartilage

• Tendons and ligaments

• Muscle

• Cortical bone

• Synovium

• Articular cartilage, fibrocartilage (aneural)

nociceptive pain

Predominantly driven by activation of peripheral nociceptive sensory fibers

• Pain pattern:

  • Localized to the area of injury/dysfunction

  • Mechanical/anatomical in nature

  • Intermittent and sharp with movement/mechanical provocation

  • Dull or throbbing at rest

• Responds well to:

  • Posture education

  • Muscle stretching

  • Joint mobilization

  • Motor control exercises

  • Muscle strengthening

neuropathic pain

Lesion or dysfunction in peripheral or central nerves

• Pain pattern:

  • Burning, shooting, stabbing, pins and needles, tingling, painful cold, electric shock

  • Dermatomal or cutaneous distribution

  • Associated with history of nerve injury, pathology, or mechanical compromise

  • Provoked with mechanical movement tests that move, load, or compress neural tissue

nociplastic pain

central sensitization

• Describes augmented CNS pain, maladaptive sensory processing and altered pain modulation

• Hypersensitive nervous system response: brain and spinal cord pain pathways become overactive and can't regulate pain signals properly

• Chronic pain cycle: increased brain activity in pain centers leads to expanding symptoms that worsen over time

• Biopsychosocial treatment approach: focus on biological, psychological, and social factors rather than just structural causes

nociceptors

transmit pain signals via A delta or C fibers

• Peripheral axon ends in the skin, cardiac and skeletal muscle, joints, and viscera

• Central axon ends dorsal horn of spinal cord

• Responsive to noxious stimuli including mechanical, chemical and thermal

  • Histamine, lactic acid buildup, prostaglandins, bradykinins, cytokines

A-Delta Fibers

• Fast pain transmission

• Occurs immediately upon contract with painful stimulus

• Myelinated and thin

  • High conduction speed

• Tells you a threat is present

  • Evoke a rapid, sharp, lancinating pain reaction, often with reflexive response

• Short-lived

• Ex: touching a hot burner on the stove

C Fibers

• Slow pain transmission

• Occurs after the A delta response

• Unmyelinated and small

  • Low conduction speed

• Slow, dull, crawling pain that is long lasting

• Poorly localized sensation

• Can create emotional and physiological responses

  • Ex: upset stomach

• Ex: the remaining pain following the initial painful stimulus of touching a hot burner on the stove

transmission of pain

Ascending nociceptive inputs from the spinal cord project to the brain and brainstem

• Spinothalamic tract

brain-neural pain matrix

pain signals are interpreted and processed in

motor control systems

movement and coordination

limbic structures

emotional processing

acute pain

• Normal physiological response: predictable reaction to chemical, thermal, or mechanical stimuli with expected recovery path

• Movement-related and position dependent: can be reproduced with movement and typically improves with rest or cessation of activity

• Red flags for systemic disease: pain that persists despite rest, occurs without trauma, or is deep/constant and worse at night

• Management

  • Appropriate management is key in preventing the progression to persistent pain

  • Prescription opioids - highly addictive

  • PT: safe and drug free pain management approach!

• Early mobilization and graded activity: progressive movement and exercise within pain tolerance to prevent deconditioning and promote tissue healing while avoiding bed rest

• Manual therapy and modalities: targeted hands-on techniques, therapeutic exercises, and evidence-supported modalities like heat/cold therapy to reduce pain and improve function

• Patient education and self-management: teaching pain science, movement strategies, and home exercise programs to empower patients and prevent chronicity through active participation in recovery

chronic pain

• No protective biological purpose: unlike acute pain, ______ pain doesn't serve a useful warning function and often limits physical activity and social participation

• Impaired pain inhibition system: the brain's natural ability to block pain signals through its pain network becomes damaged, causing pain to persist beyond normal healing timeframes

• Hypersensitized nervous system: nerve pathways become oversensitive, requiring less stimulus to trigger pain responses and perpetuating the pain cycle

pain-related beliefs

• People's understanding about what is causing their pain

• Meaning of their pain

• Expectations regarding the impact pain has on their present and future lives

beliefs associated with better outcomes

• Having control over pain

• Global self-efficacy

• Pain self-efficacy

• Control over life

• Internal pain control

beliefs associated with poor outcomes

• Pain indicates injury/damage and should be avoided

• Pain will be constant

• Pain is disabling

• Emotions influence pain

• Other people should be solicitous because of the pain, helplessness and belief that pain is controlled by someone other than them

fear avoidance model

• Proposes that some people have an exaggerated fear that movement will cause reinjury and/or increase pain

• Fear of pain can become more disabling than the pain itself

• Leads to maladaptive hypervigilance, inaccurate predictions about pain, misinterpretation of body sensations, muscular reactivity and physical deconditioning

pain persistence

• Equally dysfunctional

• Individual denies or ignores the pain

  • Often due to reluctance to rely on others or lack of social support

• Tend to have high levels of activity, overcommitment to work, and perfectionist behaviors before developing chronic pain

• Can be inflexible and often do not accept functional limitations or want to be labeled as lazy 

• Associated with cycles of overactivity -> severe pain -> forced rest -> decreased function -> overactivity

referred pain

Pain felt away from actual source: pain perceived in a different location than the underlying pathology

• Ex: Gallbladder pain felt in right shoulder

• Convergence mechanism: multiple body parts send sensory signals to the same spinal cord neuron, causing brain confusion about pain location

• Common sources: myofascial trigger points can generate secondary referred pain patterns

numerical pain rating scale (NPRS)

• Patients are asked to verbalize their perceived pain from 0 (no pain) - 10 (worst pain imaginable)

• Current, best, worst, in the past 24 hours

visual analog scale (VAS)

• 10-point numerically continuous scale that requires the pain level to be identified by making a mark on a 100-mm line from "no pain" to "worst pain imaginable" and then the distance is measured

• Can also have numbers 0 (no pain) - 10 (worst pain imaginable) and be asked to circle a value

fear avoidance

• Fear-Avoidance beliefs questionnaire

• Assess patient's beliefs about how physical activity and work affected their pain

assessing pain in children

choice of approach depends on child’s age and abilities

physiological pain assessment

• Monitor HR, BP, diaphoresis as these are more strongly associated with distress and anxiety

• Should not be used in isolation

observations of behavior

• Observing a child's nonverbal behaviors

  • Crying, facial expressions, torso and limb movements

• Observing social interactions

  • Socialization, appetite

• Useful in assessing pain in children <4 years of age who do not have language skills

self-report pain assessment

requires cognitive flexibility and working memory

SINSS

• Assessment of severity, irritability, nature, stage, stability

• Helps understand detailed aspects of a patient's symptoms for a given physical condition

• Determines rigor of examination and interventions

• Avoid under or over examining/under or overtreating the patient

• Reduces clinical reasoning errors

severity

• Intensity of the patient's pain

• Impact of the pain on activities of daily living (ADLs)

• Amount and type of pain medication taken to control the pain

• Presence or absence of night pain

minimal severity

Patient self-reported pain rating of 0-3/10

• Symptoms do not limit or hinder ADLs

• Work or recreational activities are minimally impacted

• Patient's verbal, facial, or body language indicates minimal or no pain with movement or activity

• No guarding of body regions with spontaneous movements

• Patient taking few, if any, pain-relieving medications

• No night pain

• Pain/symptom descriptions: intermittent, superficial, barely noticeable, annoying, mild or dull ache, tightness or stiffness, pulling, bothersome, or low-grade

moderate severity

Patient self-reported pain rating of 4-7/10

• Symptoms moderately impact or restrict ADLs

• Work or recreational activities are moderately impacted or restricted

• Avoidance of heavier work, recreation, or physical activities

• Patient's verbal, facial, or body language may indicate pain or guarding with movement or activity

• Pain medication: anti-inflammatory or analgesic medication may be required to function

  • Narcotics are rarely, if ever, used

• May have some sleep disturbances, but be able to return to sleep

  • May require pain medication to be able to fall asleep

• Pain/symptom descriptions: constant but variable, more persistent or frequently noticeable, throbbing, cramping, hot, burning, deep ache

maximal severity

Patient self-reported pain rating of 8-10/10

• Symptoms maximally impact or restrict ADLs

• Even basic grooming, dressing, bathing, cooking, etc. may be limited due to symptom intensity

• Work or recreational activities are maximally impacted or restricted

• Patient may be unable to work or may have stopped recreational activities all together

• Patient's verbal, facial, or body language may indicate intense pain requiring guarded movement or self-splinting of the involved body region

• Pain medication: frequent or regular use of pain medications, including narcotics, for symptom management

• Presence of night pain or significantly disturbed sleep are very likely

• Pain/symptom descriptions: constant, non-varying, burning, boring, lancinating, shooting, stabbing, knifelike, deep bone ache, sharp or severe

irritability

• Ratio of the magnitude of aggravating factors to easing factors

• Amount and type of activity to aggravate symptoms

• Amount and type of activity to ease symptoms

minimal irritability

• Ratio of at least 2:1 of aggravating activity to easing activity or rest

• Patient may tolerate activities with many repetitions, relative vigor, or sustain a posture or position for a long time before symptoms appear

• When symptoms appear, they may ease quickly with stopping activity or changing positions

moderate irritability

• Ratio of 1:1 of aggravating activity to easing activity or rest

• Patient may tolerate a moderate amount of activity, which may increase or produce symptoms that return to baseline with periods of rest or relieving motions of the same length of time as it took to bring symptoms on

• If symptoms interrupt sleep, patient may return to sleep in less than 30 min after changing positions

maximal irritability

• Ratio of 1:2 or greater of aggravating activity to easing activity or rest

• Patient may tolerate very little activity and require significant time or effort to recover from the activity

• Sleep interruptions may be frequent and prolonged, requiring greater than 30 minutes to return to sleep

• Medication may be required to be able to sleep

type/quality of pain

• Mechanical nociceptive, inflammatory nociceptive (aching)

• Neurogenic (burning)

• Central (nociplastic)

• Viscerogenic

• Autonomic

• Affective - patient characteristics and how they deal with their condition

• Other - conditions warranting special caution or action

 

red flag conditions

signs of serious pathology

yellow flag conditions

• Pain associated, psychological distress factors

• Factors that increase the risk of developing or perpetuating long-term disability and work loss associated with pain

 

stage

Timeframe in which a condition is presenting

• acute, subacute, chronic, acute on chronic, subacute on chronic

acute stage

symptom duration less than 3 weeks, recent onset

subacute stage

Symptom duration more than 3 weeks, but less than 6 weeks

chronic stage

symptom duration greater than 6 weeks

acute on chronic

• Combination of an underlying condition that is chronic (chronic mild low back pain) with an acute exacerbation or episode of more intense pain (recent reinjury of same low back region)

• Acute symptoms may also be different, but related to the chronic condition (chronic low back with acute onset of leg pain or numbness and tingling

subacute on chronic

• Combination of an underlying condition that is chronic (chronic mild elbow pain) with a subacute exacerbation or episode of more intense pain (subacute reinjury of same elbow region)

• Subacute symptoms may also be different, but related to the chronic condition (chronic elbow pain with subacute onset of forearm and wrist pain or numbness and tingling in hand)

stability

progression of the patient’s symptoms over time

• may relate to current episode or all episodes over time

symptoms: improving, worsening, not changing, waxing and waning

improving

• Overall symptom decrease in intensity, frequency, or location

• Return to regular movement or function

• Restoration of regular sleep patterns

• Less dependence on pain medication

worsening

• Overall symptom increase in intensity, frequency, or location

• Regression of movement or function

• Greater disruption of regular sleep patterns

• More dependence on pain medication

not changing

• Overall symptoms are not changing with time; no worse, no better

• Progress toward normal function may be stagnant

• No change in current sleep patterns

• No change in amount/type of pain medication

waxing and waning

• At times condition seems to be improving, but other times getting worse

• May be dependent on external factors like environment, psychosocial settings, or time of day

non-pharmacological control of pain

• Thermotherapy

• Cryotherapy

• Electrotherapy - TENS and interferential

• Manual therapy

  • Local peripheral effects as well as more systemic and CNS effects that either directly or indirectly reduce pain

• Patient education

  • Use patient-friendly language and avoid "scary" language

• Aquatics

• Exercise