The Prevalence of Latent Trigger Points in Lower Limb Muscles in Asymptomatic Subjects

Background: Latent trigger points (LTrPs) are prevalent in persons with musculoskeletal pain. Because they could be present in healthy persons, it is necessary to evaluate the prevalence of LTrPs in asymptomatic subjects. Objectives: To assess the prevalence of LTrPs in lower limb muscles, to evaluate the relationship between LTrP prevalence, gender, and leg dominance, and to determine intra-rater reliability for the diagnosis of LTrPs. Design: Cross-sectional study. Setting: University community. Patients: A total of 206 asymptomatic subjects (113 women and 93 men, aged 23.2 +/- 5.2 years). Intervention: Not applicable. Main Outcomes Measures: The prevalence of the LTrPs located in the gastrocnemius, soleus, peroneus longus, peroneus brevis, tibialis anterior, extensor digitorum longus, flexor digitorum longus, rectus femoris, vastus medialis, and vastus lateralis was studied, using the diagnosis criteria recommended by Simons, Travell, and Simons. The pressure pain threshold was also evaluated. Results: Of the 206 subjects evaluated, 166 (77.7%; 95% confidence interval [CI], 72-83.4) were found to have at least one LTrP in the lower limb muscles. The average number of LTrPs found per individual was 7.5 +/- 7.7. The prevalence in each muscle group ranged from 19.9% (95% CI, 14.4-25.4) to 37.4% (95% CI, 30.8-44), with gastrocnemius LTrPs being the most prevalent. Women had more LTrPs (9.6 +/- 7.8) than did men (4.9 +/- 6.6) (P < .01). No relationship was found between the LTrPs and leg dominance (P > .05). The most prevalent diagnosis criteria were the presence of a taut band and a tender spot (98%-100%); the local twitch response was the least prevalent diagnosis criteria (0%-3.5%). Intra-rater reliability was excellent for all the diagnosis criteria in all the muscles evaluated (kappa = 0.762-1), except for the jump sign and the referred pain in several LTrPs. Conclusion: LTrPs were prevalent in the lower limb muscles of asymptomatic subjects. Women have more LTrPs than do men. No differences in LTrP prevalence were found between sides. The presence of the taut band and the tender spot were the most prevalent and reliable diagnosis criteria. It is necessary to determine if the evaluation of LTrPs in the lower limb muscles of asymptomatic subjects has clinical relevance.