Nociplastic Pain: A Contemporary Narrative Review of Mechanisms, Clinical Assessment, Controversies, and Management.

Background: Nociplastic pain was introduced by the International Association for the Study of Pain (IASP) in 2017 as a third mechanistic descriptor alongside nociceptive and neuropathic pain, denoting pain from altered nociception without unambiguous tissue damage or somatosensory lesion. Fibromyalgia is its prototypical example; nociplastic mechanisms have also been proposed to contribute, often alongside nociceptive or neuropathic components, to irritable bowel syndrome, temporomandibular disorders, chronic primary headache, and much chronic musculoskeletal and visceral pain. Objective and Methods: This narrative review synthesizes evidence published between January 2016 and June 2026 on the mechanisms, clinical assessment, controversies, and management of nociplastic pain, integrating recent (2024-2026) conceptual debates with mechanistic and clinical data. We aimed to clarify the distinctions among central sensitization (a mechanism), nociplastic pain (a clinical-mechanistic descriptor), and chronic primary pain (a diagnosis) in a clinically usable form, to appraise the recent validation evidence for the 2021 IASP clinical criteria, and to identify research priorities for the domains in which those criteria remain unvalidated. Key Findings: The descriptor reflects central sensitization, deficient descending modulation, neuroimmune/glial activation, and maladaptive plasticity, plus increasingly recognized peripheral contributions. The 2021 IASP criteria show acceptable reliability in trained raters but uncertain performance in primary care and non-musculoskeletal domains. Management prioritizes, as first line, exercise, psychological therapy, pain neuroscience education, and multidisciplinary rehabilitation, together with centrally acting agents, although the pharmacological evidence derives largely from fibromyalgia trials; opioids and anti-inflammatory drugs are largely ineffective in predominantly nociplastic pain. Controversies concern the mechanism-versus-diagnosis distinction and the risk that an over-inclusive label obscures occult peripheral pathology. Conclusion: Nociplastic pain is a clinical-mechanistic descriptor, not a diagnosis, and is best applied as a continuous component of complex pain rather than a fixed diagnostic label. Priorities include validation of criteria beyond the musculoskeletal system, objective biomarkers, and phenotype-stratified trials.