What Is Central Sensitisation?

Defining Central Sensitisation

Central sensitisation is a state of amplified nociceptive processing within the central nervous system — primarily at the level of the spinal dorsal horn and supraspinal pain-processing centres — characterised by an abnormally low threshold for pain generation, exaggerated responses to stimuli, and the spread of pain sensitivity beyond the original site of injury or pathology.

The term was introduced and systematically characterised by Clifford Woolf, whose foundational research demonstrated that the central nervous system is not a passive relay for pain signals, but an active, plastic processor capable of undergoing significant functional and structural change in response to sustained nociceptive input. Once established, central sensitisation is capable of maintaining pain independently of peripheral tissue status — meaning pain continues even after the initial injury has fully healed.

Central sensitisation is not rare. It is present to varying degrees in a wide range of chronic musculoskeletal conditions, and its recognition fundamentally changes how a clinician should approach assessment and treatment.

The Neurobiological Mechanisms

Several converging mechanisms drive the development and maintenance of central sensitisation:

Synaptic long-term potentiation (LTP): Repeated nociceptive input to the dorsal horn induces LTP at synaptic connections between primary afferent neurones and second-order neurones. LTP — the same mechanism underlying memory formation — increases synaptic efficiency, meaning future inputs produce larger and more prolonged responses. The pain system, in effect, learns to amplify.

N-methyl-D-aspartate (NMDA) receptor activation: Under conditions of sustained nociceptive input, NMDA receptors at dorsal horn synapses are unblocked, allowing calcium influx that drives downstream molecular changes — phosphorylation of receptor subunits, gene expression changes, and synaptic remodelling — that persistently lower the threshold for dorsal horn neurone activation.

Loss of descending inhibition: The brain normally exercises top-down control over spinal pain processing through descending inhibitory pathways using serotonin, noradrenaline, and endogenous opioids. In central sensitisation, these inhibitory systems become less effective, reducing the brain's capacity to modulate incoming nociceptive signals.

Glial cell activation: Microglia and astrocytes within the spinal cord and brain, when activated by sustained pain signalling, release pro-inflammatory cytokines and neuromodulators that amplify central sensitisation and can maintain it even after peripheral nociceptive input has ceased.

How It Presents Clinically

Central sensitisation produces a characteristic clinical pattern that distinguishes it from primarily peripheral or nociceptive pain:

• Allodynia: Pain produced by stimuli that are not ordinarily painful — light touch, clothing contact, or gentle pressure over areas previously not involved in the original injury.
• Hyperalgesia: Exaggerated, disproportionate pain in response to normally mild painful stimuli.
• Temporal summation (wind-up): Repeated application of the same stimulus produces progressively increasing pain — an analogue of the NMDA-mediated wind-up occurring at the spinal level.
• Widespread pain: Pain that extends beyond the anatomical distribution of the original injury, reflecting the expanded receptive fields of sensitised central neurones.
• Disproportionate pain behaviour: Reports of severe pain in response to clinical testing that would ordinarily be expected to produce minimal or no discomfort.
• Fatigue, cognitive disruption, and sleep disturbance: The neuroinflammatory and neuroendocrine changes associated with central sensitisation extend beyond pain pathways, affecting broader brain function.

Conditions Where CS Is Present

Central sensitisation is a transdiagnostic mechanism — it is not a diagnosis itself, but a neurophysiological state present across many clinical conditions. It is well-documented in fibromyalgia, where it is considered the primary pathomechanism; in chronic widespread pain; in persistent post-surgical pain; in whiplash-associated disorder; and as a secondary feature complicating many regional musculoskeletal conditions including chronic low back pain, cervicogenic headache, knee osteoarthritis, and lateral epicondylalgia when pain has been present for extended periods.

Identifying Central Sensitisation

Clinical assessment of central sensitisation relies on pattern recognition rather than a single diagnostic test. The Central Sensitisation Inventory (CSI) provides a validated screening questionnaire. Quantitative sensory testing (QST) — including pressure pain threshold measurement and conditioned pain modulation assessment — provides objective data on sensitisation and descending inhibitory capacity. Clinically, the presence of widespread hypersensitivity, disproportionate pain responses, and a broad symptom constellation extending beyond the musculoskeletal system raises the index of suspicion.

Management Principles

Because central sensitisation is a central nervous system state rather than a tissue pathology, treatment directed solely at peripheral structures is typically insufficient. Effective management addresses the nervous system itself. Pain neuroscience education reduces the threat value attributed to pain, diminishes catastrophising, and supports a shift from passive to active coping. Graded activity and exposure progressively restore the brain's experience of safe movement, providing counter-evidence to the sensitised system's threat appraisal. Aerobic exercise activates endogenous opioid and serotonergic pain modulation systems. Sleep optimisation and stress reduction reduce the neuroinflammatory and neuroendocrine contributors to sensitisation. Manual therapy and dry needling serve as adjuncts by providing peripheral sensory input that modulates central processing and supports engagement with active rehabilitation.