The myofascial trigger point (MTrP) is the hallmark physical finding of the myofascial pain syndrome (MPS). The MTrP itself is characterized by distinctive physical features that include a tender point in a taut band of muscle, a local twitch response (LTR) to mechanical stimulation, a pain referral pattern characteristic of trigger points of specific areas in each muscle, and the reproduction of the patient's usual pain. No prior study has demonstrated that these physical features are reproducible among different examiners, thereby establishing the reliability of the physical examination in the diagnosis of the MPS. This paper reports an initial attempt to establish the interrater reliability of the trigger point examination that failed, and a second study by the same examiners that included a training period and that successfully established interrater reliability in the diagnosis of the MTrP. The study also showed that the interrater reliability of different features varies, the LTR being the most difficult, and that the interrater reliability of the identification of MTrP features among different muscles also varies.

Simons' integrated hypothesis proposed a model of trigger point (TrP) activation to explain known TrP phenomena, particularly endplate noise. We propose an expansion of this hypothesis to account for new experimental data and established muscle pathophysiology.