Mechanics of pelvic girdle stability and self-bracing in SIJ-related pelvic girdle pain: a review

Background:Pelvic girdle mechanics and control is a rapidly evolving area of research. Our traditional understandings were firmly grounded in theory borrowed from the fields of engineering (mechanical and structural) but have since began to branch out into neuroscience and motor control. The melding of mechanical concepts with those of neuroscience have led to a much better understanding of the effect of pain on the function of the pelvic girdle, specifically functional load transfer. Yet our understanding of the aetiology of pain particularly, chronic pain and recurrent pain pathways, is elusive.Objectives:The aim of the current review was to assess the mechanical and motor control components to pelvic girdle stability and propose a hypothetical model for mechanical aetiology of chronic posterior pelvic girdle pain.Results:A potentially new paradigm is offered on the current models of insufficient versus excessive force closure. The proposed model takes into account dynamic movement scenarios where the effect of anticipatory postural adjustment (APA) would be responsible for engaging local muscles to effectively elicit self-bracing of the sacroiliac joints (SIJ) for load transfer. When this mechanism fails the system would rely on compensatory postural adjustment (CPA) reliant on aberrant global muscle activation to stiffen the lumbar–pelvic–hip complex.Conclusions:For load transfer to be successful the pelvic girdle must be stabilized. The author has shown how disturbance of a component of this dynamic link may destabilize and disrupt the load transfer mechanism, resulting in low back pain of SIJ origin.