The main aim of this paper is to investigate the phenomenology and pathophysiology of trigger points. I start by a description of how the concept is defined in relation to scientific research and clinical use. Through electronic search in databases such as PubMed, Cochrane and UpToDate I have extracted relevant research papers on this topic. I have also looked into existing, authorative literature in this field. In addition to this, I have interviewed a clinician who works in this area on a daily bases to get an understanding of how trigger points are diagnosed in the clinic.The outcome of this study reveals that, while there is good empirical evidence that trigger points exist, there is limited consensus with respect to diagnostic criteria. Neither is there a common understanding of the etiology and pathophysiology of trigger points. Several theories exist, but none seems to meet the criteria of a well-founded scientific understanding. Still, the etiology of pain in trigger points is not known, but it seems likely that central sensitization plays a key role.Further research is needed to test the validity and reliability of the criteria for diagnosing trigger points as they are used today, in order to achieve a common platform for clinical use. Further investigation into the pathophysiological mechanism is also needed in order to reach a thorough understanding, which is a prerequisite for effective treatment.