Ankle and foot — Reference values: Regional protocol, Achilles tendon — anteroposterior thickness, Plantar fascia — thickness at calcaneal origin.
Targeted category for pain, trauma, tendons, ligaments, plantar fascia, forefoot and inflammatory Doppler. There is no single universal system for every ankle and foot finding; therefore the reading uses green for clearly usual measurements and pattern, yellow for borderline or pain/dynamic-dependent findings, and red for tear, instability, infection, neurovascular compression, complicated diabetic foot or structurally abnormal findings.
Use a high-frequency linear transducer; assess long and short axis, painful point, dynamic maneuvers, contralateral comparison and Doppler when inflammatory pain, mass, tenosynovitis or infection is suspected.Source: AIUM Practice Parameter for Musculoskeletal Ultrasound; ESSR ankle and foot technical guideline
Achilles tendon — anteroposterior thickness
up to about 6 mm
The limit varies by sex, age, sports load and measurement site. Thickness alone does not diagnose tendinopathy; values above 6 mm, hypoechogenicity, fibrillar loss, Doppler or focal pain increase suspicion.usual if echotexture is normal: ≤6 mmborderline/contextual: >6–8 mmlikely abnormal if symptomatic: >8 mm ou defeitoSource: Scientific Reports 2021 Achilles normative data; AIUM MSK parameter
Plantar fascia — thickness at calcaneal origin
<4 mm
Below 4 mm favors normality. Many studies use 4 mm as a sensitive cutoff; others find higher specificity with 4.5 to 5 mm. For safety, 4 to 4.9 mm is yellow and 5 mm or more is red when typical pain is present.strong normality: <4 mmborderline: 4–4,9 mmthickened if pain matches: ≥5 mmSource: Musculoskeletal ultrasound plantar fasciitis reviews; IJGM 2024; POCUS/ACEP heel pain teaching
Morton interdigital neuroma — largest axis
size alone does not decide mm
Lesions larger than 5 mm are more likely clinically relevant, but small symptomatic neuromas and asymptomatic lesions exist. Pain, Mulder click, dynamic compression and relation to intermetatarsal bursa matter more than size alone.less specific if isolated: <4 mmcorrelate with pain: 4–5 mmprobably relevant if symptomatic: >5 mmSource: Foot and ankle ultrasound reviews; Morton neuroma imaging studies
Synovitis and tenosynovitis — Doppler
0–3 B-mode and Doppler
Use low scale, high gain without artifact and minimal compression. Grade 1 may be contextual; Doppler or synovial hypertrophy grades 2-3 are abnormal in inflammatory context.absent: 0mild/contextual: 1active/abnormal: 2–3Source: EULAR-OMERACT synovitis scoring; AIUM MSK parameter
When ultrasound is not enough
focal bone pain, inability to bear weight, occult fracture, osteomyelitis or surgical planning
Radiography, CT or MRI may be needed depending on trauma, diabetic foot, bone concern, surgical plantar plate concern or complex tear.Source: ACR Appropriateness Criteria chronic ankle pain / acute foot trauma; AIUM MSK parameter
Classifications and calculators
Interactive assistant — ankle and foot
Input
How to use
Limitation
Green
Achilles up to 6 mm, plantar fascia <4 mm, no defect, no synovial Doppler and no warning sign.
Only valid if technique and clinical context agree.
Yellow
Achilles >6-8 mm, fascia 4-4.9 mm, neuroma 4-5 mm, partial sprain, tenosynovitis or grade 1 synovitis.
Compare, test dynamically and correlate with the painful point.
Red
Tendon tear, dynamic instability, fascia ≥5 mm with typical pain, symptomatic neuroma >5 mm, synovitis/Doppler grade 2-3, infection, complicated diabetic foot or neurovascular compression.
Do not close as a variant; describe extent and guide correlation/referral.
The calculator is educational. It helps organize findings, but the final impression depends on the clinical question, physical examination, technique and contralateral comparison.