Pain Mechanisms

1. inputs to the system

2. processing of inputs

3. outputs from the CNS

Mature Organism Model – Review

what is inputs to the system?

– Include sensory afferents and environmental context
– Nociceptive inputs from body tissues
– Peripheral nerve-related pain

what is processing of inputs?

– Occurs from the dorsal horn to cortical centers
– Involves central pain mechanisms
– Influencing factors:

• Past experiences, Social and cultural context, Pain beliefs and knowledge, Expectations and fear, Other psychosocial elements

what is output from the CNS?

– Construction of the pain experience
– Other physiological and behavioral responses

what is three types of pain?

• nociceptive 

• peripheral neuropathic 

• central (nociplastic) 

what is nociceptive pain?

• Proportionate Pain

• Aggravating and easing factors

• Intermittent sharp, dull ache, or throb at rest

• No night pain, dysesthesia, burning, shooting or electric pain

what is Peripheral Neuropathic Pain?

• Pain in dermatomal or cutaneous distribution
• Positive neurodynamic tension testing and palpation
• History of nerve pathology or compromise

• Disproportionate pain

• Disproportionate aggravating factors

• No easing factors

• Diffuse tenderness to palpation

• Psychosocial Issues
  – Fear avoidance
  – Pain catastrophizing
  – Depression

Central Sensitization (Nociplastic Pain)

• pain referred in a dermatomal or cutaneous distribution 

• history of nerve injury, pathology, or mechanical compromise 

• pain/symptom provocation mechanical testing which moves, loads, or compresses neural tissue

peripheral neuropathic 

• pain localized to area of injury or dysfunction +/- somatic referral

• clear proprotionate mechanical or anotomical nature to agg/eases

• usually intermittent and sharp with movement or mechanical provocation 

• absence of:

  • pain with other dysesthesias 

  • night pain or disturbed sleep 

  • burning, shooting, or electrical pain

nociceptive

• disproportionate, non-mechanical unpredictable pain pattern in response to multiple or non specific aggs/eases

• pain disproportionate to the nature and extent of injury or pathology 

• diffuse/non anatomic area of pain/ tenderness on palpation 

• strong association with maladaptive psychosocial factors

central nocioplastic

• shows the relative contributions of different pain mechanisms in a patient’s experience

• dynamic 

  • size of each “slice” can change over time based on biological, psychological, and social factors

• help understand the dominant pain mechanism 

  • tailor assessment and treatment strategies

pain pies

Pain Mechanisms - Key Points

• Patient 1 – Nociceptive-Dominant

•  Presentation: Acute low back pain after lifting a heavy object.

•  Pain Pie:

  • Red (Nociceptive): Large portion – tissue damage, inflammation.

  • Blue (Peripheral Neuropathic): Small – mild nerve irritation.

  • Green (Nociplastic): Small – minimal central sensitization.

• Clinical Focus: Address tissue healing, inflammation, and movement education

Case Example 1

• Patient 2 – Peripheral Neuropathic- Dominant

• Presentation: Radiating leg pain with numbness and tingling.

• Pain Pie:

  • Blue (Peripheral Neuropathic): Large portion – nerve root involvement.

  • Red (Nociceptive): Small – some mechanical irritation.

  • Green (Central Nociplastic): Small – early signs of central involvement.

• Clinical Focus: Nerve mobility, reduce mechanical compression, education on nerve pain.

Case Example 2

• Patient 3 – Central Nociplastic-Dominant

• Presentation: Chronic low back pain for over a year, widespread sensitivity, poor sleep, and fear of movement.

• Pain Pie:

  • Green (Central Nociplastic): Large portion – central sensitization, altered pain processing.

  • Red (Nociceptive): Small – minimal tissue damage.

  • Blue (Peripheral Neuropathic): Small – no clear nerve involvement.

• Clinical Focus: Pain neuroscience education, graded exposure, cognitive-behavioral strategies.

Case Example 3

• Traditional Time-Based Categories:

• Updated Understanding

• Clinical Implication:

Acute, Sub-Acute and Chronic Pain

Traditional Time-Based Categories:

– Acute Pain: Present for less than 3 months.
– Subacute Pain: Lasts between 6 weeks and 3 months.
– Chronic Pain: Persists for more than 3 months.

what is Updated Understanding?

– Central sensitization/nociplastic pain can develop within days after injury.
– Time alone is not a reliable indicator of pain mechanism.

acute, sub-acute and chronic pain Clinical Implication:

– Therapists must recognize that persistent pain can begin early.
– Early identification of central mechanisms is crucial for effective treatment.