F ear is a universal and powerful emotion and, as a result, it can have a profound impact on human behavior. A common assumption is that fear motivated behavior is in the best interest of the individual or group. However, literary and historical quotations suggest deleterious consequences can be associated with behaviors primarily motivated by fear. For example, François La Rochefoucauld (1613-1680) penned, ''We promise according to our hopes and perform according to our fears.'' In addition, Franklin Roosevelt famously delivered, ''The only thing we have to fear is fear itself-nameless, unreasoning, unjustified terror which paralyzes needed efforts to convert retreat into advance,'' during his 1933 inaugural speech.Then it is not surprising to consider that fear-motivated behavior has the potential to adversely impact rehabilitation outcomes for patients with musculoskeletal pain. In 1983, a group of psychologists, physical therapists, and occupational therapists presented a theoretical model that described the influence fear had on pain outcomes. 15 Specifically, Lethem et al 15 proposed the Fear-Avoidance Model of Exaggerated Pain Perception (FAMEPP), and hypothesized that pain-related fear was integral to the development of chronic musculoskeletal pain syndromes.The central tenet of the FAMEPP was that pain perception had sensory and emotional reaction components. 15 The sensory component of pain was mediated by physiological factors related to the level of nociceptive input. The emotional reaction component of pain was mediated by psychological factors primarily related to fear of pain. Patients with lower levels of pain-related fear were hypothesized to have a synchronous relationship between sensory and emotional reaction components. Confrontation of pain symptoms was expected with a synchronous relationship and this was believed to be an adaptive response, resulting in a timely return to prior functional levels. 15 In contrast, patients with higher levels of pain-related fear were hypothesized to have a desynchronous relationship between the 2 pain components. Avoidance of pain symptoms was expected with a desynchronous relationship and this was believed to be a maladaptive response, associated with exaggerated pain perception and, eventually, chronic disability.
15These theoretical delineations made the FAMEPP amenable to hypothesis testing and, subsequently, numerous empirical studies reported in the peer review literature have supported the theoretical structure of the model for patients with musculoskeletal pain. Cross-sectional studies consistently documented a positive association between elevated pain-related fear and increased pain intensity and disability. 2,4,22 In addition, several longitudinal studies indicated that elevated pain-related fear is a precursor to poor clinical outcomes. 7,13,20 In my opinion, the FAMEPP has had a meaningful impact on the study of musculoskeletal pain because it clearly hypothesized that elevated pain-related fear and associated avoidance were not adaptive respon...