ABSTRACT
Painful musculoskeletal disorders are a common problem in today’s society, affecting an estimated one-
third of the population. The societal costs (including litigation, work-lost, treatment and disability) for
painful musculoskeletal disorders are staggering. Financially, considering all chronic pain syndromes
together, there is an annual cost of $90 billion.2 For example, the cost of low back pain alone has
been estimated between $40-50 billion annually.20,21 Until a better understanding of the pathomechan-
isms in chronic pain and the injuries which cause them is defined, the effective prevention and treatment
of these disorders and their symptoms will remain elusive. It is the intent of this chapter to review and
highlight traditional and more recently emerging theories explaining pain sensation, signaling and trans-
mission in the context of injury and musculoskeletal disorders.
