Objectives: Myofascial trigger points (MTrPs) are considered the principal clinical feature of myofascial pain syndrome (MPS). An MTrP consists of spot tenderness within a taut band of muscle fibers and its stimulation can produce both local and referred pain. The clinical diagnosis of MPS depends on correct history taking and a physical examination aimed at identifying the presence of MTrP. The purpose of this study was to investigate the intra-rater reliability of a palpation protocol used for locating an MTrP in the upper trapezius muscle.
Methods: Twenty-four subjects with MTrP in the upper trapezius muscle were examined by an experienced physiotherapist. During each of eight experimental sessions, subjects were examined twice in randomized order using a palpation protocol. An anatomical landmark system was defined and the MTrP location established using X and Y values.
Results: The intraclass correlation coefficient ICC(1,1) values were 0.62 (95% CI: 0.30-0.81) for X and 0.81 (95% CI: 0.61-0.91) for Y. The Bland-Altman plots for X and Y showed a mean of difference of 0.04 and -0.2 mm, respectively. Limits of agreement for X ranged from -26.3 to 26.2 mm and for Y from -27 to 26.4 mm.
Discussion: The ICC(1,1) for the observed values revealed a moderate to high correlation and the Bland-Altman analysis showed means of difference very close to zero with narrow limits of agreement. An experienced physiotherapist can reliably identify MTrP locations in upper trapezius muscle using a palpation protocol.
Keywords: Intra-rater reliability; Myofascial pain syndromes; Myofascial trigger points; Palpation; Upper trapezius muscle.