RESUMO
Chronic nonspecific low back pain (LBP) is a complex and multifaceted problem. The following Perspective piece tries to help make sense of this complexity by describing a model for the development and maintenance of persistent LBP that integrates modifiable factors across the biopsychosocial spectrum. The Fit-for-Purpose model posits the view that chronic nonspecific LBP represents a state in which the person in pain holds strong and relatively intransient internal models of an immutably damaged, fragile, and unhealthy back, and information that supports these models is more available and trustworthy than information that counters them. This Perspective proposes a corresponding treatment framework for persistent pain that aims to shift internal models of a fragile, damaged, unhealthy, and unchangeable self toward the formulation of the back as healthy, strong, adaptable, and fit for purpose and to provide the system with precise and trustworthy evidence that supports this supposition while minimizing information that works against it.