Table 1 –

Ultrasound studies by imaging technique

B-mode only (N = 9)
Author	Population	Total No. of participants No. of sites/images Males : Females	Use of Control Groups	Use of Travell and Simons’ criteria	MTrP property measured
Cojocaru et al. 2015	Patients with low back pain	N = 8 Not reported Not reported	No control group of participants No mention of control sites	Not reported	Area
Da Silva et al. 2020	Patients with shoulder pain and MTrPs in upper trapezius muscles	N = 40 Not reported 14:26	No control group of participants No comparison to normal tissue	Yes	Area
Jafari et al. 2017	Cervicogenic headache patients	N = 19 Not reported All female	No control group of participants Adjacent muscle tissue used for comparison	Yes	Elastic modulus, area
Jafari et al. 2018	Patients with a MTrP in the SCMa muscle	N =29 Not reported All female	No control group of participants Adjacent muscle tissue used for comparison	Yes	Elastic modulus
Khumbare et al. 2020	Patients with MPS and MTrPs aged 20 to 50	N = 32 N = 282 images 8:7 (controls)	Fifteen healthy controls simultaneously recruited, no mention of age or sex-matching	Not reported	Texture analysis features
Khumbare et al. 2017	Neck pain patients aged between 20 and 65 years	N = 30 Not reported 5:10 (symptomatic)	Fifteen healthy controls simultaneously recruited, no mention of age or sex-matching	Yes	Texture analysis features
Taheri et al. 2016	Participants with symptoms of MPS aged 30–50, BMI 22–25 kg/m2	N = 15 Not reported 4:11	Four healthy controls found among the fifteen participants	Yes	Area, Echogenicity
Togha et al. 2020	Cervicogenic headache patients	N = 29 Not reported All female	No specific control group of participants, comparison between treatment groups	Yes	Elastic modulus, area
Zale et al. 2015	Participants aged 18–65	N = 25 N = 500 sites 11:14	Eight healthy controls found among the twenty-five participants	Yes	Area
Vibration Sonoelastography (external, mechanically induced vibrations) (N = 6)
Author	Population	Total No. of participants No. of sites/images Males : Females	Use of Control Groups	Use of Travell and Simons’ criteria	MTrP property measured
Ballyns et al. 2011	Cervical pain patients with an active or latent MTrP in the upper trapezii muscles	N = 44 N = 169 sites Not reported	No control group of participants, sites without MTrPs served as controls	Yes	Areas of increased stiffness from elastograms (quantified with scoring system)
Ballyns et al. 2012	Cervical pain patients with an active MTrP in the upper trapezii muscles	N = 22 Not reported 11:11	Nine healthy participants with no neck pain, no mention of matching	Yes	Shear wave velocity, shear modulus
Sikdar et al. 2009	Participants with at least one active MTrP in the upper trapezius muscles	N = 9 N = 33 sites 2:7	No control group of participants, adjacent muscle tissue was used for comparison	Yes	Area and stiffness (quantified with a scoring system)
Takla et al. 2016	Current physical therapy patients aged 25–45	N = 50 N = 312 MTrPs Not reported	No control group of participants, adjacent muscle tissue was used for comparison	Yes	Stiffness (as strain scores/ratios)
Turo et al. 2013	Participants with neck pain for past three months and at least one MTrP in the upper trapezius muscles	N = 29 N = 232 images 13:16	Fifteen healthy controls simultaneously recruited, no mention of age or sex-matching	Yes	Entropy, stiffness
Turo et al. 2015	Participants with at least one palpable nodule in the upper trapezius muscle	N = 48 N = 96 sites 18:30	No control group of participants	Yes	Stiffness via a mechanical heterogeneity index (fraction of elastogram area with decreased vibration)
Shear Wave Elastography (SWE) (N = 2)
Author	Population	Total No. of participants No. of sites/images Males : Females	Use of Control Groups	Use of Travell and Simons’ criteria	MTrP property measured
Grabowski et al. 2018	Participants with a single unilateral latent MTrP in the infraspinatus muscle	N = 18 N = 9 sites 6:12	Healthy controls, age and sex matched	Yes	Shear wave speed (SWS)
Maher et al. 2013	Women with palpable MTrPs in the upper trapezius muscle	N = 7 N = 7 MTrPs All female	No control group of participants	Not reported	Elastic modulus
Compression sonoelastography (manual technique) (N = 2)
Author	Population	Total No. of participants No. of sites/images Males : Females	Use of Control Groups	Use of Travell and Simons’ criteria	MTrP property measured
Calvo-Lobo et al. 2017	Non-specific lumbopelvic pain patients	N = 10 N = 60 sites 9:1	No control group of participants, sites without MTrPs served as controls	Not reported	Stiffness (measured as manual strain index)
Müller et al. 2015	Women aged 20–40 years with at least one active MTrP in both the right and left trapezius muscles	N = 24 N = 48 MTrPs All female	No specific control group of participants, comparison between treatment groups	Yes	Stiffness (measured as strain ratio), area
Doppler (N = 3)
Author	Population	Total No. of participants No. of sites/images Males : Females	Use of Control Groups	Use of Travell and Simons’ criteria	MTrP property measured
Ballyns et al. 2011	Cervical pain patients with an active or latent MTrP in the upper trapezii muscles	N = 44 N = 169 points Not reported	No control group of participants. sites without TrPs served as controls.	Yes	Resistive Index, Pulsatility Index
Sikdar et al. 2009	Participants with at least one active MTrP in the upper trapezius muscles	N = 9 N = 33 sites 2:7	No control group of participants, adjacent muscle tissue was used for comparison	Yes	Resistive Index
Sikdar et al. 2010	Participants with at least one active MTrP in the upper trapezius muscles	N = 16 N = 74 sites Not reported	No control group of participants, adjacent muscle tissue was used for comparison	Yes	Resistive Index, Pulsatility Index, Acceleration Time, and Time Averaged Peak Velocity
Other Studies (N = 3)
Author	Population	Total No. of participants No. of sites/images Males : Females	Use of Control Groups	Use of Travell and Simons’ criteria	MTrP property measured
Aridici et al. 2016 B-mode, sonoelastography (details not specified) Treatment evaluation (HPPTb ultrasound vs. DNc)	Participants with at least one A-MTrP in the upper trapezius muscle	N = 61 Not reported 8:53	No specific control group of participants, comparison between treatment groups	Yes	Stiffness (pixel intensities in MTrP ROIs)
Kumbhare et al. 2018 B-mode sonography with 10s video at 30 fps	Neck pain patients with palpable taut band or nodule in the upper trapezius muscle, aged between 20–65	N = 61 N = 18,300 ROIs (300 images per subject * 61 subjects) Not reported	Twenty-four aged-matched controls	Yes	Texture analysis features
Behr et al. 2015 B-mode sonography with video	Musculoskeletal pain outpatient clinic patients with regional neck pain and a palpable TrP in the upper trapezius aged 20–65	N = 69 N = 917 images 38:31	Twenty-nine healthy controls, aged matched	Yes	Texture analysis features used in binary SVMd classifiers of MTrPs and normal muscle

^aSternocleidomastoid.

^bHigh- power pain threshold.

^cDry needling.

^dSupport vector machine.