Adult hip — Reference values

Adult hip — Reference values: Minimum adult hip protocol, Transducer and depth, Hip effusion — anterior capsule/femoral neck distance, Iliopsoas bursa.

Adult hip ultrasound is a region-based targeted examination. It is very useful for anterior effusion, synovium, iliopsoas bursa, gluteal tendons, peritrochanteric bursae, dynamic snapping, collections, superficial masses and guided procedures. It does not reliably exclude labrum, deep cartilage, femoroacetabular impingement and deep bone; radiographs and MRI remain important in those scenarios. Colors separate consensus normality, gray-zone/divergent findings and abnormal or high-risk findings.

Measurements and reference values

Measurement	Usual value	Note
Minimum adult hip protocol	anterior, lateral, medial, posterior and dynamic when indicated	Anteriorly, align the transducer with the femoral neck for the anterior recess and iliopsoas. Laterally, assess the greater trochanter, gluteus medius, gluteus minimus, fascia lata and bursae. Medially, assess adductors/distal iliopsoas. Posteriorly, assess proximal hamstrings and sciatic nerve.Source: AIUM-ACR-SPR-SRU musculoskeletal ultrasound parameter / ESSR hip technical guideline
Transducer and depth	highest frequency that penetrates adequately	Deep hip, obesity and arthroplasty may require a curvilinear or lower-frequency transducer. Use low-scale Doppler and light compression when the question is synovitis, infection or collection.Source: AIUM-ACR-SPR-SRU musculoskeletal ultrasound parameter
Hip effusion — anterior capsule/femoral neck distance	5–7 mm	There is divergence: practical protocols use >5 mm or a 2 mm side difference; classic musculoskeletal literature uses 7 mm or more, and some osteoarthritis studies use 8 mm. Measure along the femoral neck axis and compare with the opposite side when possible.Green: <5 mm and no relevant asymmetryYellow: 5-6.9 mm or 1-1.9 mm side differenceRed: >=7 mm or >=2 mm side difference; urgency depends on fever, trauma, prosthesis or complex fluidSource: Ann Rheum Dis 2000 / Emory Emergency Ultrasound / AJR 2003 / Scientific Reports 2020
Iliopsoas bursa	normally collapsed/not visible	When visible, look for communication with the joint, pelvic extension, relation to femoral vessels and femoral nerve compression.Green: not visibleYellow: simple distention or associated tendinopathyRed: complex, bulky, infected, hemorrhagic or with neural/vascular compressionSource: ESSR hip guideline / International Journal of Sports Physical Therapy 2024
Peritrochanteric bursae	normally not visible	Lateral hip pain is rarely just bursitis; greater trochanteric pain syndrome often involves gluteus medius or minimus tendinopathy, with or without bursa.Green: bursa not visible and tendons preservedYellow: simple bursa, tendinopathy or calcificationsRed: complete tear, retraction, complex collection or possible infectionSource: ESSR hip guideline / Br J Gen Pract 2017 review
Gluteus medius and minimus tendons	fibrillar and continuous	Assess at the greater trochanter in long- and short-axis. Describe which tendon/facet is involved, thickening, hypoechogenicity, calcification, cleft, gap, retraction and Doppler.Source: AIUM-ACR-SPR-SRU / ESSR hip guideline / GTPS review
Snapping hip — dynamic maneuver	reproduce the movement causing the snap	Internal snapping usually involves iliopsoas over the iliopectineal/femoral prominence; external snapping involves fascia lata or gluteus maximus over the trochanter. If labral/intra-articular snapping is suspected, ultrasound is limited.Source: AIUM-ACR-SPR-SRU / IJSPT iliopsoas review / AJR dynamic snapping hip
Osteoarthritis — ultrasound-accessible signs	osteophytes, superficial deformity and effusion/synovitis	Ultrasound can show anterior osteophytes and deformity, but it does not replace radiography for osteoarthritis grading or MRI when cartilage/labrum are the question.Source: Scientific Reports 2020 / BMJ Open hip osteoarthritis ultrasound
Painful hip arthroplasty	effusion, collection, mass, pseudotumor and tendons	Ultrasound helps detect collections and guide aspiration when periprosthetic infection is suspected, but an isolated finding does not replace laboratory, radiographic and orthopedic correlation.Source: AIUM-ACR-SPR-SRU / AJR prosthetic hip infection sonography

Classifications and calculators

Interactive assistant — adult hip ultrasound

Input	Output	How to use
Normal measurements, nonvisible bursae, continuous tendons and no alert	Green	Use when the question is soft tissue/effusion and the regional protocol was documented.
5-6.9 mm recess, mild asymmetry, tendinopathy, simple bursitis or reproduced snapping	Yellow	Describe as contextual, compare with the opposite side and suggest complementary imaging if the question is deep.
>=7 mm, >=2 mm difference, complex fluid, arthroplasty collection, complete tear, fracture, deep mass or possible infection	Red	Communicate the relevant finding and route to guided aspiration, radiograph, CT, MRI or specialist assessment according to context.

Fill measurements, fluid quality, Doppler, iliopsoas, lateral tendons, bursa, visible bone, posterior region, arthroplasty and alerts to generate a color reading.

Source: AIUM-ACR-SPR-SRU / ESSR / Ann Rheum Dis / AJR / GTPS review

Anatomic roadmap by region

Region	What to assess	Pitfalls
Anterior	Hip recess, capsule, visible anterior labrum, iliopsoas, iliopsoas bursa, femoral vessels and femoral nerve when indicated.	Do not call capsular thickness synovitis without seeing fluid/synovium; compare sides.
Lateral	Greater trochanter, gluteus medius, gluteus minimus, fascia lata, gluteus maximus and bursae.	Lateral pain is often gluteal tendinopathy with or without bursa, not just “bursitis”.
Medial	Adductors, pubis, distal iliopsoas, pectineus and groin structures when the complaint allows.	Hernia and athletic pubalgia may mimic hip-joint pain.
Posterior	Proximal hamstrings, ischial tuberosity, gluteus maximus, sciatic nerve and deep masses.	Deep window may be limited; do not exclude neural compression from an incomplete exam.
Dynamic	Reproduce the movement causing snapping/pain: flexion, extension, rotation, abduction or adduction according to complaint.	If the snap is intra-articular, labrum and loose bodies are better assessed by MRI.

Source: AIUM-ACR-SPR-SRU / ESSR hip technical guideline

Hip effusion and synovitis — color reading

Finding	Green	Yellow	Red
Capsule/femoral neck distance	<5 mm	5-6.9 mm	>=7 mm; some studies use 8 mm
Contralateral comparison	<1 mm difference	1-1.9 mm	>=2 mm in practical protocols; >=1 mm in some studies
Fluid quality	no fluid or simple trace	simple effusion	debris, septa, gas, pus, blood or suspicious postoperative setting
Synovial Doppler	no flow	mild/moderate	intense with fever, prosthesis, wound or disabling pain

In adults, ultrasound detects distention and guides aspiration, but small effusion may be difficult and etiology is not defined by ultrasound alone.

Source: Ann Rheum Dis 2000 / AJR 2003 / Emory Emergency Ultrasound

Lateral hip pain — greater trochanteric pain syndrome

Structure	Normal/low risk	Caution	High risk
Gluteus medius/minimus	fibrillar and continuous	thickening, hypoechogenicity, calcification or partial cleft	complete tear, retraction or important atrophy
Trochanteric bursa	not visible	small simple distention	complex, hyperemic or possible infection
Fascia lata/gluteus maximus	smooth gliding	reproduced external snapping	disabling pain, associated tear or mass

Clinical review emphasizes that lateral trochanteric pain should not be reduced to “bursitis”; gluteal tendinopathy is common.

Source: Br J Gen Pract 2017 / ESSR / AIUM

Anterior pain, iliopsoas and snapping

Pattern	Ultrasound clue	Practical reading
Normal iliopsoas	striated muscle, echogenic tendon and nonvisible bursa	Green if pain is not reproduced and no collection is present.
Iliopsoas tendinopathy	thickening, hypoechogenicity, focal pain or Doppler	Describe along the course and relation with bursa.
Internal snapping	iliopsoas tendon snaps dynamically during the maneuver	Record movement used and whether it reproduced pain.
Complex/bulky bursa	deep collection between iliopsoas and capsule, possibly extending to pelvis	Assess infection, bleeding, joint communication and femoral compression.

Source: ESSR / IJSPT iliopsoas review / AJR dynamic snapping hip

Painful arthroplasty and priority-changing findings

Scenario	Ultrasound finding	Teaching action
Possible infection	effusion/collection, complex fluid, hyperemia, wound or fever	Communicate and consider guided aspiration according to local protocol.
Mass or pseudotumor	periprosthetic mass, deep extension or neurovascular relation	Measure, map extent and suggest complementary imaging.
Trauma or fracture	cortical step, avulsion, deep hematoma or inability to bear weight	Radiograph/CT or orthopedic assessment according to scenario.
Arthroplasty limitation	artifact, shadowing, depth or pain prevents complete assessment	Do not exclude deep complication; record limitation.

Source: AIUM-ACR-SPR-SRU / AJR prosthetic hip infection sonography

Useful adult hip differential diagnoses

Complaint	Ultrasound possibilities	When to remember another modality
Anterior/groin pain	effusion, synovitis, iliopsoas, bursa, adductors, hernia or lymph node	Labrum, cartilage, impingement and avascular necrosis require MRI/radiograph.
Lateral pain	gluteal tendinopathy, bursa, external snapping, calcification or mass	Lumbar/radicular pain may mimic trochanteric pain.
Posterior pain	proximal hamstrings, sciatic nerve, hematoma or deep mass	Neurologic deficit, deep mass or avulsion requires complementary imaging.
Fever or inability to bear weight	effusion, synovitis, collection, abscess or complicated prosthesis	Do not delay aspiration/urgent assessment when clinical concern is strong.

Source: AIUM / ESSR / Ann Rheum Dis / GTPS review

Adult hip report checklist

Item	Question the report should answer
Technique	Were side, transducer, assessed region, position, contralateral comparison and dynamic maneuver when indicated described?
Measurements	Were anterior recess, asymmetry, bursa, collection, mass or tendon gap measured when present?
Limitations	Does the report state that labrum, deep cartilage, impingement and deep bone are not well excluded by ultrasound?
Alert	Is there communication for possible infection, arthroplasty collection, complete tear, fracture, deep mass or neural compression?

Source: Best-practice synthesis from AIUM / ESSR / AJR / clinical reviews

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