Elbow — Reference values

Elbow — Reference values: Minimum elbow protocol, Technique and comparison, Common extensor tendon — thickness, Common extensor tendon — cross-sectional area.

Elbow ultrasound should be read by compartments: anterior, lateral, medial, posterior, nerves and dynamic maneuvers when indicated. Numeric tendon cutoffs vary across series; therefore isolated thickening is yellow, while tear, avulsion, infection, neuropathy with deficit, deep mass and instability are red.

Measurements and reference values

Measurement	Usual value	Note
Minimum elbow protocol	anterior + lateral + medial + posterior	add ulnar nerve, radial nerve, Doppler and dynamic maneuvers when clinically indicatedSource: AIUM/ACR/SPR/SRU 2017; ESSR
Technique and comparison	high-frequency linear transducer	scan in long and short axis; compare with the opposite side when measurement, pain or morphology is borderlineSource: AIUM/ACR/SPR/SRU 2017; ESSR
Common extensor tendon — thickness	< 4,2 mm	green if fibrillar and without focal pain; 4.2 mm or more is yellow because it is a practical cutoff, not a universal standalone consensusSource: Radiology/AJR series; ESSR technique
Common extensor tendon — cross-sectional area	< 32 mm²	32 mm² or more supports lateral epicondylalgia when there is hypoechogenicity, fissure, calcification, cortical irregularity or painSource: Radiology/AJR series
Common flexor-pronator tendon	no universal cutoff	use thickness, echotexture, residual fibers, enthesopathy, Doppler and contralateral comparisonSource: ESSR; AIUM/ACR/SPR/SRU 2017
Ulnar nerve at cubital tunnel — cross-sectional area	< 8 verde · 8–9,9 amarelo · ≥10 vermelho mm²	10 mm² or more is a widely used practical cutoff; confirm with symptoms, morphology, elbow-to-forearm ratio and nerve conduction when neededSource: Bayrak 2009; expert consensus 2021
Elbow-to-forearm ulnar nerve area ratio	< 1,3 verde · 1,3–1,49 amarelo · ≥1,5 contextual	do not use alone; it supports focal swelling when absolute area and symptoms agreeSource: Peripheral nerve ultrasound literature
Olecranon bursa	normally collapsed or not visible	any distension is contextual; thick wall, debris, gas, hyperemia, wound or fever raise it to redSource: AIUM/ACR/SPR/SRU 2017; ESSR
Elbow effusion/synovitis	no single universal number	effusion is yellow; with trauma, mechanical locking, fever, crystals, inflammatory arthritis or intense Doppler it may be redSource: AIUM/ACR/SPR/SRU 2017
Distal biceps and triceps	assess continuity, gap and retraction	complete tear, avulsion or traumatic gap is red; tendinopathy/partial tear is yellowSource: AIUM/ACR/SPR/SRU 2017; ESSR
Elbow ligaments	dynamic stress when indicated	assess the lateral complex and ulnar collateral ligament; dynamic opening, avulsion or clinical instability is redSource: ESSR; AIUM/ACR/SPR/SRU 2017

Classifications and calculators

Interactive assistant — elbow ultrasound

Color	When to use	Teaching action
Green	Measurement below practical cutoff and preserved morphology	Record the compartment protocol and comparison when performed
Yellow	Thickening, small effusion, tendinopathy, simple bursitis, mild Doppler or finding without universal numeric consensus	Describe morphology, pain, opposite side and limitation; avoid absolute conclusion from an isolated number
Red	Complete tear, avulsion, infection, neuropathy with deficit, deep mass, mechanical locking or dynamic instability	Measure extent/gap/retraction, document Doppler/dynamics and recommend urgent correlation according to context

The assistant uses colors to separate consensus normality, gray zone and clearly abnormal findings. It does not replace clinical judgment, radiographs, MRI or electrodiagnostic testing when the question is bone, deep intra-articular or neurophysiologic.

Source: AIUM/ACR/SPR/SRU 2017; ESSR; peripheral nerve ultrasound consensus

Anatomic roadmap by compartment

Compartment	Required structures	Attention point
Anterior	Anterior recess, humeroradial/humeroulnar joint, distal biceps, brachialis, vessels and nerves when indicated	Effusion, synovitis, loose body, bicipitoradial bursa and distal biceps tear
Lateral	Lateral epicondyle, common extensor tendon, lateral ligament complex, radial head/neck and radial nerve	Lateral epicondylalgia, partial/complete tear, calcification, fissure and varus instability
Medial	Medial epicondyle, common flexor-pronator tendon, ulnar collateral ligament and ulnar nerve at cubital tunnel	Assess nerve flexion/extension and valgus stress when indicated
Posterior	Triceps, olecranon, olecranon bursa and posterior recess	Bursitis, triceps tear, posterior impingement, osteophyte and loose body
Nerves and dynamics	Ulnar nerve, radial nerve and posterior interosseous branch according to symptoms	Cross-sectional area, proximal/distal caliber, focal compression, subluxation and snapping triceps

Source: AIUM/ACR/SPR/SRU 2017; ESSR elbow technical guideline

Tendons and ligaments — color reading

Structure	Green	Yellow	Red
Common extensor tendon	fibrillar, thin, no focal pain	thickness ≥4.2 mm, area ≥32 mm², hypoechogenicity, calcification or small fissure	high-grade/complete tear, avulsion or traumatic gap
Common flexor-pronator tendon	fibrillar and symmetric	tendinopathy, enthesopathy, calcification or partial tear	high-grade/complete tear or medial avulsion
Distal biceps	continuity to radial tuberosity	tendinopathy, bicipitoradial bursitis or partial tear	complete tear, retraction or avulsion
Triceps	fibrillar, preserved insertion	tendinopathy, enthesophyte or partial tear	complete tear, avulsion or extensor deficit
Ulnar collateral ligament and lateral complex	continuous and without dynamic opening	thickening, pain and mild/contextual laxity	avulsion, dynamic opening, symptomatic throwing athlete or clinical instability

Source: ESSR; AIUM/ACR/SPR/SRU 2017

Nerves, Doppler and dynamic maneuvers

Item	Green	Yellow	Red
Ulnar nerve — cross-sectional area	<8 mm² and fascicular	8-9.9 mm² or elevated ratio without deficit	≥10 mm², focal compression, hourglass or motor deficit
Ulnar nerve dynamics	stable during flexion/extension	asymptomatic subluxation or mild snapping	symptomatic dislocation, painful snapping triceps or neurologic deficit
Doppler	no hyperemia	mild/moderate hyperemia in tendinopathy, bursa or synovitis	intense hyperemia with fever, wound, complex bursa or possible septic arthritis
Radial nerve or posterior interosseous branch	fascicular, no compression	enlargement or pain without deficit	motor deficit, compression by mass/cyst or suspected denervation

Source: ESSR; peripheral nerve ultrasound consensus

Useful elbow differential diagnoses

Dominant symptom	Common possibilities	What ultrasound should look for
Lateral pain	lateral epicondylalgia, lateral complex injury, radiocapitellar osteoarthritis, radial nerve	common extensor tendon, calcifications, cortex, ligament and posterior interosseous branch
Medial pain	medial epicondylalgia, ulnar collateral ligament, ulnar nerve, throwing athlete	common flexor-pronator tendon, valgus stress, ulnar nerve area and dynamics
Posterior pain or swelling	olecranon bursitis, gout, infection, triceps, posterior impingement	bursa, wall, debris, Doppler, triceps and posterior recess
Trauma with pop	distal biceps tear, triceps tear, avulsion, occult fracture	tendon continuity, gap, retraction, effusion and cortex; radiograph if bone concern
Paresthesia or weakness	ulnar neuropathy, radial neuropathy or compression by mass/cyst	cross-sectional area, caliber, focal compression, dynamics, mass and denervated muscles
Stiffness, locking or effusion	synovitis, loose body, crystals, osteoarthritis, infectious arthritis	recesses, Doppler, erosions, visible loose body and systemic warning signs

Source: AIUM/ACR/SPR/SRU 2017; ESSR

Teaching checklist for the elbow report

Step	Record
1. Indication and side	lateral, medial, posterior or anterior pain, trauma, neuropathy, rheumatology, postoperative setting or procedure
2. Compartments	anterior, lateral, medial and posterior; state if any was not assessed
3. Tendons and ligaments	thickness, echotexture, residual fibers, calcification, gap, retraction, enthesis and dynamic stress
4. Nerves and Doppler	ulnar nerve, radial nerve/posterior interosseous branch, cross-sectional area, dynamics and hyperemia
5. Limitations	ultrasound does not replace radiographs/MRI for deep bone, cartilage, deep intra-articular loose body or complex instability

Source: AIUM/ACR/SPR/SRU 2017; ESSR

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