Neurophysiology of Musculoskeletal Pain

Abstract

Musculoskeletal pain presentation is distinct from cutaneous and visceral pain, which is typified by pricking, burning, or cutting sensations which are easily localized to their point of origin. In contrast, musculoskeletal pain presents as cramping and aching sensations which are not easily localized and sometimes referred to other parts of the body. This chapter reviews our current clinical understanding of the origins and physical manifestation of musculoskeletal pain. Additionally, we address the cellular and molecular triggers of musculoskeletal pain and the neurological pathways of muscular pain conduction. Musculoskeletal pain arising from mechanical overload or overuse is classified as either acute or chronic. Acute forms of musculoskeletal pain include type I muscle strain and delayed onset muscle soreness (DOMS). These forms of acute musculoskeletal pain differ in the timing of onset (immediate vs. up to 24 h) and duration (hours vs. weeks), but are both generally easily localizable and relatively transient. In contrast, chronic musculoskeletal pain, which is often accompanied by hyperalgesia, is often referred to a location other than the muscle of origin and often arises from repeated muscle damage. This chapter describes two common disorders with chronic musculoskeletal components—myofascial pain syndrome (MPS) and fibromyalgia. MPS is typified by the formation of chronically contracted taut bands, or trigger points, in the affected muscle following recurrent muscle strain. MPS progression leads to hypersensitivity and referred pain. In contrast, musculoskeletal pain associated with fibromyalgia arises from groups of muscles with distinct tender points, but without the taut bands associated with MPS.