Inter- and Intraexaminer Reliability in Identifying and Classifying Myofascial Trigger Points in Shoulder Muscles

Arch Phys Med Rehabil. 2018 Jan;99(1):49-56. doi: 10.1016/j.apmr.2017.06.020. Epub 2017 Jul 24.


Objective: To determine inter- and intraexaminer reliability of examiners without clinical experience in identifying and classifying myofascial trigger points (MTPs) in the shoulder muscles of subjects asymptomatic and symptomatic for unilateral subacromial impact syndrome (SIS).

Design: Within-day inter- and intraexaminer reliability study.

Setting: Physical therapy department of a university.

Participants: Fifty-two subjects participated in the study, 26 symptomatic and 26 asymptomatic for unilateral SIS.

Interventions: Two examiners, without experience for assessing MTPs, independent and blind to the clinical conditions of the subjects, assessed bilaterally the presence of MTPs (present or absent) in 6 shoulder muscles and classified them (latent or active) on the affected side of the symptomatic group. Each examiner performed the same assessment twice in the same day.

Main outcome measures: Reliability was calculated through percentage agreement, prevalence- and bias-adjusted kappa (PABAK) statistics, and weighted kappa.

Results: Intraexaminer reliability in identifying MTPs for the symptomatic and asymptomatic groups was moderate to perfect (PABAK, .46-1 and .60-1, respectively). Interexaminer reliability was between moderate and almost perfect in the 2 groups (PABAK, .46-.92), except for the muscles of the symptomatic group, which were below these values. With respect to MTP classification, intraexaminer reliability was moderate to high for most muscles, but interexaminer reliability was moderate for only 1 muscle (weighted κ=.45), and between weak and reasonable for the rest (weighted κ=.06-.31).

Conclusions: Intraexaminer reliability is acceptable in clinical practice to identify and classify MTPs. However, interexaminer reliability proved to be reliable only to identify MTPs, with the symptomatic side exhibiting lower values of reliability.

Keywords: Myofascial pain syndromes; Pain, referred; Rehabilitation; Shoulder impingement syndrome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Clinical Competence
  • Deltoid Muscle
  • Female
  • Humans
  • Male
  • Middle Aged
  • Muscle, Skeletal*
  • Myofascial Pain Syndromes / therapy
  • Observer Variation*
  • Pectoralis Muscles
  • Reproducibility of Results
  • Rotator Cuff
  • Shoulder
  • Single-Blind Method
  • Superficial Back Muscles
  • Trigger Points*
  • Young Adult