Associative memory for movement-evoked chronic back pain and its extinction with musculoskeletal physiotherapy

Chronic, non-specific, low back pain is a disabling, costly, poorly understood and treated clinical problem. The failure of earlier structure-based mechanisms to explain its cause or guide successful treatment, along with the identification of a large psychosocial component, led to the recommendation that it best be managed using a cognitive-behavioural approach. As a result, typical conservative treatment includes a combination of 'advice' and an exercise-based intervention such as musculoskeletal physiotherapy. However, recent proposals notwithstanding, both the mechanism(s) for (chronic) pain, as well as response to this type of intervention, remain unclear. The following review presents the hypothesis that, with at least some cases, mechanically evoked symptoms and signs of chronic non-specific low back pain are the product of a sustained associatively learned memory for pain and its behavioural responses. With susceptible individuals, this memory is being inappropriately reinforced by both cognitive emotional factors, and pain-associated proprioceptive (not inflammatory nociceptive) afferent input continually generated in the periphery. Together, the verbal and physical strategies employed by musculoskeletal physiotherapy are proposed to be capable of extinguishing the associatively learned pain memory. They do so by effectively changing 'top-down' (cognitive-emotional) and 'bottom-up' (afferent input) sources of reinforcement. Extinction is, therefore, likely to be a neurological mechanism underlying the clinical efficacy of this type of intervention.