Musculoskeletal / soft tissue — Reference values

Musculoskeletal / soft tissue — Reference values: Soft-tissue mass — minimum documentation, Mass size, Relationship to fascia and depth, Typical cyst, ganglion or bursa.

Soft-tissue ultrasound should work as safe triage: confirm whether there is a lesion, localize the anatomic layer, measure in three planes, assess relationship with fascia, muscle, tendon, joint, vessels and nerves, and separate typical benign findings from indeterminate or suspicious masses. Do not promise benignity when there is doubt.

Measurements and reference values

Measurement	Usual value	Note
Soft-tissue mass — minimum documentation	three measurements, layer, fascia, margins, composition and Doppler	include history, growth, pain, trauma, anticoagulation, punctum/discharge, reducibility and comparison when usefulcomplete: two projections, three planes and Dopplerincomplete: no layer, no fascia or no Dopplerunsafe: calling benign without typical criteriaSource: BMUS 2024 / ESSR 2015 / SRU 2022
Mass size	<5 versus ≥5 cm	5 cm is a classic trigger for MRI/specialist assessment, but smaller masses may still be malignant if deep, growing or atypicalsmall typical: <5 cm and typical benignitynot decisive: <5 cm but solid/indeterminatealert: ≥5 cmSource: ESSR 2015 / sarcoma guidelines / BMUS 2024
Relationship to fascia and depth	superficial, contacts fascia, crosses fascia or intramuscular/deep	below superficial fascia, intramuscular or not fully accessible by ultrasound favors MRItypical superficial: entirely subcutaneous and fully seenfascial contact: broad base or difficult deep margindeep: crosses fascia, intramuscular or not fully seenSource: ESSR 2015 / BMUS 2024
Typical cyst, ganglion or bursa	anechoic, thin-walled, posterior enhancement, no solid component and no internal vascularity	if there are internal echoes, thick wall, nodularity or vascularity, it becomes indeterminatetypical: pure avascular cysticcomplex: debris, thin septa or inflammatory contextsolid/nodular: vascularized componentSource: ESSR 2015 / BMUS 2024 / SRU 2022
Typical superficial lipoma	oval/elliptic, well-defined, compressible, parallel to skin, echogenic or striated, without relevant vascularity	deep, large, heterogeneous, painful or growing lipoma should not be treated as simpletypical: superficial and stableatypical: heterogeneous or symptomaticnot simple: deep, ≥5 cm or rapid growthSource: SRU 2022 / ESSR 2015 / BMUS 2024
Collection, hematoma or abscess	context + compressibility + internal echoes + peripheral Doppler	hematoma should decrease on follow-up; abscess often has pain, redness, fever or peripheral hyperemiaclear trauma: regressing hematomacomplex collection: follow-up or drainage by clinical contextinfection/expansion: fever, gas, severe pain or growthSource: BMUS 2024 / Radiol Clin North Am 2019
Median nerve — wrist cross-sectional area	<9–10 mm²	≥10 mm² suggests carpal tunnel; interpret with symptoms and proximal/distal comparisonusual: <9–10 mm²borderline: 10–12 mm²enlarged: >12 mm²Source: J Ultrasound Med / MSK ultrasound reviews
Achilles tendon — thickness	4–6 mm	>7 mm suggests tendinopathy when associated with fibrillar-pattern loss, pain or hyperemiaSource: IJSPT / AJR

Classifications and calculators

Interactive assistant — soft tissue, differential and next steps

Input	How the app interprets it	Limitation
Typical benign	Simple cyst/ganglion, typical superficial lipoma, foreign body with compatible history or clear dynamic hernia.	Use only if all typical criteria are present.
Indeterminate	Nonlipomatous solid, complex collection, small but atypical mass, vascularity or nonconclusive anatomic relationship.	Ultrasound should not close the diagnosis when there is overlap.
Suspicious or urgent	Deep, larger than 5 cm, growing, fixed, invasive margins, disorganized vascularity, recurrence after excision or severe infectious signs.	MRI/specialist referral according to local pathway.

Use as educational triage. The result lists possibilities, not a definitive diagnosis.

Source: SRU Radiology 2022 / BMUS 2024 / ESSR 2015 / ACR 2022

Differential by ultrasound pattern

Pattern	Common possibilities	Sign that changes management
Pure avascular cystic	Simple cyst, ganglion, distended bursa, synovial cyst.	Solid component, mural nodule or internal vascularity.
Typical superficial fatty	Superficial lipoma.	Deep, ≥5 cm, heterogeneous, painful or growing.
Nonlipomatous solid	Fibroma, nerve sheath tumor, giant cell tumor of tendon sheath, lymph node, scar endometriosis, fibromatosis.	Infiltrative margins, growth or disorganized vascularity.
Complex collection	Hematoma, seroma, abscess, Morel-Lavallée, complicated bursitis.	Fever, redness, gas, severe pain, expansion or no regression.
Vascular or compressible	Venous/lymphatic malformation, varix, pseudoaneurysm, hemangioma.	Pulsatile arterial flow, fistula, thrombus or high flow.
Dynamic with Valsalva	Hernia, muscle herniation, expansile varix.	Entrapment, marked pain, nonreducible or compromised bowel loop.
Echogenic with shadow or foreign body	Foreign body, granuloma, calcification, myositis ossificans, tophus.	Intramuscular calcification or associated mass: radiography/MRI depending on context.
Deep or invasive mass	Sarcoma and other aggressive tumors enter the differential until proven otherwise.	MRI and oncology/sarcoma referral pathway.

Source: SRU 2022 / BMUS 2024 / ESSR 2015

Warning signs — when not to close as benign

Sign	Why it matters	Color
Larger than 5 cm	Classic trigger for additional workup, especially if solid.	Red
Deep, intramuscular or crosses fascia	Ultrasound may not see full extent; MRI is preferred.	Red
Rapid growth or post-excision recurrence	Increases suspicion and changes biopsy/referral pathway.	Red
Invasive margins or disorganized vascularity	Morphologic sign of aggressiveness, although not specific alone.	Red
Isolated pain	May be inflammatory/traumatic, but is also a clinical warning sign if associated with a solid mass.	Yellow
Calcification	Occurs in benign and malignant lesions; if in an extremity or within muscle, radiography helps.	Yellow

Source: ESSR 2015 / BMUS 2024 / ACR 2022

Technical checklist — soft-tissue ultrasound

Step	Report	Reason
Targeted history	Duration, growth, pain, trauma, anticoagulation, fever/redness, punctum/discharge, reducibility and prior surgery/cancer.	Changes the differential.
Anatomic location	Side, exact point, layer: skin, subcutaneous, fascia, muscle, tendon, joint, vessel or nerve.	Avoids a generic report.
Images and measurements	Two orthogonal projections, three measurements, depth, image of deep margin and contralateral comparison if useful.	Enables follow-up.
B-mode and Doppler	Composition, echogenicity, margins, enhancement/shadowing, calcification, compressibility, peripheral/internal flow.	Separates cystic, solid, inflammatory and vascular.
Dynamic maneuvers	Compression, tendon/muscle motion, Valsalva, standing position when hernia/varix is a hypothesis.	Shows functional relationship.
Safe conclusion	Typical benign, indeterminate or suspicious; if indeterminate, clearly state that correlation/additional imaging is needed.	Protects patient and physician.

Source: BMUS 2024 / ESSR 2015 / SRU 2022

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