About Joni E. Rabiner, MD

Professor of Pediatrics (in Emergency Medicine)
Department of Emergency Medicine
Division of Pediatric Emergency Medicine
Columbia University Irving Medical Center / Morgan Stanley Children's Hospital

PEM POCUS Series: Pediatric Musculoskeletal Ultrasound

PEM POCUS pediatric musculoskeletal badge

Read this tutorial on the use of point of care ultrasonography (POCUS) for pediatric musculoskeletal evaluation. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.

Module Goals

  1. List the indications for performing pediatric musculoskeletal (MSK) point-of-care ultrasound (POCUS)
  2. Describe the technique for performing specific pediatric MSK POCUS applications
  3. List anatomical landmarks for specific MSK POCUS applications
  4. Interpret signs of fracture, effusion, dislocation, and osteomyelitis with POCUS
  5. Describe the limitations of MSK POCUS

Case Introduction: Adolescent with Left Knee Swelling

A 13-year-old female with no past medical history presents to the emergency department with pain and swelling to her left knee. The pain started 3 days ago, with the pain worsening and swelling noted on the day prior to arrival. She can bear weight but has a limp. She has had no other current or past joint pain or swelling, no known trauma, no fever or other infectious symptoms, no recent travel, and no known insect or tick bites. She spent the summer at camp in the northeast United States. Her vaccines are up to date.

On arrival, her vital signs are:

Vital Sign Finding
Temperature 37.3 C
Heart rate 109 bpm
Blood pressure 117/74
Respiratory rate 20
Oxygen saturation (room air) 99%

On physical examination, she is well appearing and in no acute distress. Her exam is significant for left knee swelling and tenderness to palpation anteriorly with decreased knee flexion due to pain. She has no redness, warmth, or numbness around her knee. She has an antalgic gait but can bear weight.

Given her pain and swelling of her left knee, blood tests and X-rays are ordered, and orthopedics is consulted. You decide to perform a musculoskeletal point-of-care ultrasound (MSK POCUS) examination.

Musculoskeletal POCUS can be performed for a variety of indications including trauma, swelling, erythema, pain, decreased range of motion of a joint, and limp or inability to bear weight. It can assist in early diagnosis of fracture, effusion, dislocation, and osteomyelitis and allow for expedited treatment. Children and adolescents are ideal candidates for MSK POCUS as they generally have less subcutaneous tissue, making it easier to obtain ultrasound images to assess for pathology.

Note: This module focuses on diagnostic uses in musculoskeletal POCUS and not on procedural uses.

Musculoskeletal POCUS can be incorporated into the physical examination by scanning the area of injury, the point of maximal pain or tenderness, or a joint for effusion.

Probe Selection and Patient Comfort

Linear ultrasound probe

Figure 1. Linear ultrasound probe.

  • Use a high frequency linear probe (Figure 1) to obtain high resolution images of generally superficial structures in MSK POCUS.
    • A curvilinear probe may be necessary for older children to examine structures with depth greater than 4-6 cm (e.g., hip).
  • Patient comfort is the key to obtaining quality images.
    • Place in a position of comfort on the bed, chair, or in a parent’s lap.
    • Apply copious warm gel (Figure 2L).
    • Rest the base of your scanning hand on a non-tender area to avoid putting excessive pressure on a painful area (Figure 2R).
    • Provide pain control.
    • Distract with a toy, book, or phone/tablet.
    • Consult a child life specialist, if available, to help ease the child’s anxiety.
Linear probe with gel and floating probe technique

Figure 2. Linear probe with copious gel (L). The clinician floats the probe on the gel and rests the base of the scanning hand on an uninjured area to minimize pressure on the painful area (R).

Pro-Tips

  1. When performing MSK POCUS, it is helpful to scan the contralateral normal side first. This allows for identification of the child’s normal anatomy, including growth plates if present, and comparison when scanning the area of pain/injury. It also allows the child to understand the MSK POCUS exam before scanning the painful area.
  2. Match the probe footprint to the area being scanned: a wider, longer footprint for the hips or long bones; a smaller footprint for the small bones of the hands or feet.
Musculoskeletal POCUS is excellent at identifying fractures of long bones (e.g., radius and ulna); however, it is less reliable for identifying fractures at joints, epiphyses, and the small bones of the hands and feet, where curved, irregular contours make imaging with POCUS more difficult. Additionally, non-displaced physeal fractures (Salter-Harris I) may be missed by POCUS.

Technique

To evaluate for fracture, dislocation, or osteomyelitis, place a linear transducer over the desired area to identify changes to the bony contour or alignment.

  • Look everywhere. Scan bones circumferentially as much as possible and in perpendicular planes (longitudinal and transverse axes) to avoid missing pathology. Fractures may escape detection if the transducer is placed parallel to the course of the fracture.
  • Scan the contralateral side for comparison. This is especially crucial when the pathology involves or is adjacent to a physis.
  • Use the water bath technique. Submerge the injured extremity in a basin of water to facilitate imaging of the small bones of the hands and feet (Figure 3). The probe does not need to be in contact with the injured area in a water bath, and the probe is submersible up to the point where the electrical cord exits the probe.
Water bath technique to image a phalanx dorsally and ventrally with the submerged probe floating above the hand

Figure 3. Water bath technique to image a phalanx dorsally (L) and ventrally (R), with the submerged probe floating just above but not touching the injured hand.

Normal finger phalanx imaged with water bath technique

Figure 4. Normal finger phalanx imaged with the water bath technique, with the probe not touching the finger and approximately 1 cm of anechoic fluid between the probe and the finger. Air bubbles may be visible in the water.

Figure 5. Ultrasound clip of a normal finger phalanx using the water bath technique.

Normal Findings

Normal bone is seen as a hyperechoic line with posterior acoustic shadowing.

Normal physis:

  • Longitudinal view (Figure 6): Appears as a V-shaped, hypoechoic, uniform band of cartilage between the metaphysis and epiphysis that is symmetric with the contralateral side.
  • Transverse view (Figure 7): Appears as a regular but ragged area between the hyperechoic curvilinear metaphysis and epiphysis of the bone.

Longitudinal view of normal physis showing V-shaped hypoechoic band between metaphysis and epiphysis

Figure 6L. Longitudinal view of a normal physis. The hypoechoic band of cartilage forms a smooth V-shape between the hyperechoic metaphysis and epiphysis (yellow arrows: physis above, bone below). Compare with the contralateral side to confirm symmetry.

Figure 6R. Longitudinal scanning of a normal physis.

Transverse view of normal physis with regular but ragged appearance between metaphysis and epiphysis

Figure 7L. Transverse view of a normal physis. The cartilage band appears regular but ragged between the curvilinear hyperechoic metaphysis and epiphysis (yellow arrows: physis above, bone below).

Figure 7R. Transverse scanning of a normal physis.

Ultrasonography can reliably detect diaphyseal (long bone) fractures including the forearm, lower leg, and clavicle. It is also useful for detection of other fractures.

1. Long Bone Fracture

  • Longitudinal view (Figure 8): A fracture is visualized as a disruption in the bony cortex with a discontinuity or step-off. There may be associated periosteal changes, periosteal fluid, or hematoma. Angulation and displacement of the fracture fragments may be measured.
  • Transverse view (Figure 9): The fracture site is identified by an irregularity in the hyperechoic, curvilinear bony cortex and/or a “jump” in the location of the bone as the fracture site is crossed.
  • Ultrasound can detect fractures as small as 1 mm [1].
  • In the forearm and lower leg, be sure to scan both bones at the site of injury to avoid missing a fracture.

Pediatric distal radius fracture in longitudinal view showing cortical step-off with physis distal to the fracture

Figure 8L. Forearm fracture in longitudinal view. An angulated, displaced distal radius fracture is shown, with the physis visible distal to the fracture site.

Figure 8R. Longitudinal scanning of a distal radius fracture.

Pediatric distal radius fracture in transverse view showing irregular curvilinear bony surface with both edges of the fracture site visible

Figure 9L. Forearm fracture in transverse view. The fracture site shows an irregular curvilinear bony surface with both edges of the fracture visible.

Figure 9R. Transverse scanning of a distal radius fracture.

2. Buckle Fracture

  • A buckle fracture appears as a small “bump” in the linear bone cortex, usually without any discontinuity of the bone (Figure 10).

ultrasound finger fracture

Figure 10L. Two examples of buckle fracture of the distal radius (arrows). Top: small “bump” in the bony cortex without discontinuity. Bottom: a second buckle fracture of the distal radius in longitudinal view.

Figure 10R. Buckle fracture of the distal radius.

3. Finger Phalanx Fracture

  • The discontinuity of the cortex of a phalanx may be seen in longitudinal and transverse views (Figures 11 and 12).
  • A fracture appears as a break in the hyperechoic cortex, in contrast to a joint, which is regular and similar to adjacent fingers or to the contralateral normal side.

Pediatric finger phalanx fracture imaged in a water bath showing discontinuity of the bony cortex with FRACTURE and JOINT labeled

Figure 11. Discontinuity of the bony cortex of the phalanx (arrow) in a water bath, consistent with fracture. The adjacent joint is regular and intact.

Figure 12L. Longitudinal scanning of a phalanx fracture.

Figure 12R. Transverse scanning of a phalanx fracture.

4. Metacarpal Fracture

  • The discontinuity of the cortex of a metacarpal may be seen in longitudinal and transverse views (Figure 13).

Figure 13L. Cortical discontinuity (arrow) in a metacarpal fracture, with periosteal fluid (asterisk) adjacent to the fracture site.

Figure 13R. Scanning of a metacarpal fracture.

5. Nasal Fracture

  • The nasal bones may be identified, with fractures appearing as a discontinuity of the bone (Figures 14, 15, and 16). Use copious gel to facilitate imaging in this superficial, highly curved area and to minimize pain to the affected area.

Linear ultrasound probe positioning to evaluate for a pediatric nasal fracture

Figure 14. Linear probe positioning to evaluate for a nasal fracture.

Transverse ultrasound of a normal pediatric nasal bone (L) and a pediatric nasal fracture with cortical discontinuities indicated by yellow arrows (R)

Figure 15. Transverse view of a normal nasal bone (L) and a nasal fracture with cortical discontinuities (arrows, R).

Figure 16. Transverse scan of a nasal fracture.

6. Healing Fracture

  • Healing fractures will have a discontinuity in the bone with varying degrees of periosteal thickening and callus formation (Figures 17 and 18). The callus will be hypoechoic initially and will become more hyperechoic over time.

Longitudinal ultrasound of a healing distal radius fracture with periosteal thickening and callus

Figure 17L. Healing distal radius fracture in longitudinal view, with periosteal thickening and callus formation.

Figure 17R. Longitudinal scan of a healing distal radius fracture.

Transverse ultrasound of a healing distal radius fracture with periosteal thickening and callus

Figure 18L. Healing distal radius fracture in transverse view, with periosteal thickening and callus formation.

Figure 18R. Transverse scan of a healing distal radius fracture.

For evaluation of a joint effusion, the linear or curvilinear transducer is used to identify anechoic or hypoechoic fluid in the joint space. POCUS identifies the effusion but cannot distinguish hemorrhagic, infectious, or inflammatory etiologies; labs and/or advanced imaging are needed for further work-up.

POCUS of the lower extremity can assess for hip, knee, or ankle effusions. Findings must be interpreted with the clinical presentation and physical examination. For hip effusions, the Kocher criteria may be used to evaluate for septic hip.

1. Hip

  • See the ALiEM module on POCUS: Hip Effusion for more detail.
  • Positioning and probe placement: With the child’s leg in slight external rotation, place the linear transducer on the anterior hip parallel to the long axis of the femoral neck. Point the probe marker toward the patient’s head (Figure 19L).
  • Normal findings
    • Identify the hyperechoic curvilinear femoral head (+/- physis), hyperechoic linear femoral neck, and the posterior surface of the iliopsoas muscle (Figure 19R).
    • Look for fluid/effusion between the femoral neck and the posterior surface of the iliopsoas muscle. Normally a femoral fat pad sits in this space.

Linear ultrasound probe positioning on the anterior hip (L) and normal hip anatomy showing the femoral head with open physis, femoral neck, and iliopsoas muscle (R)

Figure 19. Linear probe positioning to evaluate for hip effusion (L) and normal hip anatomy (R). The arrow points to the femoral head physis.

Figure 20. Longitudinal scanning of a normal hip.

  • Abnormal finding: Hip effusion
    • Location: Anechoic or hypoechoic fluid located between the femoral neck and the iliopsoas muscle (Figure 21).
    • Measurement: A convex fluid collection measuring >5 mm (or >2 mm difference from the contralateral normal side) is positive for a hip effusion.
      • There is debate regarding measurement technique for hip effusion, with measurement of the hypoechoic fluid directly vs. measurement from the anterior surface of the femoral neck to the posterior surface of the iliopsoas muscle. However, clinically significant effusions will likely be positive (>5 mm) regardless of measurement technique, and asymmetry compared to the contralateral normal hip will usually be evident.

Hip effusion with anechoic fluid layering over the femoral neck measured to 5.7 mm, with femoral head, open physis (arrow), and iliopsoas muscle (asterisk) visible

Figure 21. Hip effusion with anechoic fluid layering over the femoral neck measured to 5.7 mm. Also visible are the femoral head with an open physis (arrow) and the iliopsoas muscle (*).

Figure 22. Longitudinal scanning of the hip showing a hip effusion.

2. Knee

  • Positioning and probe placement: Place the linear transducer longitudinally on the anterior distal femur, just superior to the patella, in the midline over the quadriceps tendon. Point the probe marker toward the patient’s head (Figure 23L). This single, longitudinal view of the suprapatellar bursa, which has direct communication with the knee joint, is the most sensitive for identifying a knee effusion (Figure 24). You may also fan the probe in longitudinal and transverse views to further evaluate the suprapatellar bursa for effusion.
    • Place a towel roll under the knee to provide about 30 degrees of knee flexion, the optimal position for detecting a knee effusion.
    • Avoid excessive pressure: pressure from the probe can compress the suprapatellar bursa and mask a small effusion.
    • To avoid missing a small effusion, milk fluid downward, medially, and/or laterally toward the probe to push fluid into the suprapatellar bursa. Hold the probe lightly while doing this.

Linear probe positioning over the anterior distal femur with a towel under the knee (L) and normal knee anatomy showing quadriceps tendon, cartilage around the patella, and femur (R)

Figure 23. Linear probe positioning to evaluate for knee effusion. Note the towel under the knee for slight knee flexion (L). Normal knee anatomy showing the quadriceps tendon (arrows) and cartilage around the patella (asterisk) (R).

Anatomic diagram of the bursae of the knee, highlighting the suprapatellar bursa contiguous with the knee joint space

Figure 24. Normal bursae anatomy at the knee. The suprapatellar bursa is contiguous with the knee joint space [2].

Figure 25. Longitudinal scanning of a normal knee.

  • Normal findings
    • Identify the linear, hyperechoic distal femur (+/- physis), the patella, and the quadriceps tendon attaching to the patella (Figure 23R). There is a pre-femoral fat pad between the femur and the quadriceps tendon. Look for a fluid collection in this suprapatellar space.
    • The patella ossifies at approximately 3-6 years of age, so younger children may still have a cartilaginous patella. The patella appears hypoechoic and may not have posterior acoustic shadowing. Do not confuse the cartilaginous patella with a joint effusion.
  • Abnormal finding: Knee effusion
    • Location: Anechoic or hypoechoic fluid sits in the suprapatellar bursa between the femur and the quadriceps tendon (Figure 26).
    • Measurement: Fluid measuring >2 mm in height is positive for a knee effusion.

Figure 26. Two examples of a knee effusion with anechoic fluid (*) between the femur and the quadriceps tendon (L) and with measurement of effusion (R).

Figure 27. Longitudinal scanning of a knee effusion.

3. Ankle

  • Positioning and probe placement: Place the linear transducer in the longitudinal axis anteriorly over the ankle joint in the midline. Point the probe marker toward the patient’s head (Figure 28L) to evaluate the tibiotalar joint. The tibiotalar joint is the area most likely to identify an effusion. Interrogate the entire joint by fanning the probe in longitudinal and transverse views to avoid missing an effusion.
  • Normal findings
    • Identify the curvilinear hyperechoic lines with posterior acoustic shadowing of the tibia and talus bones and the “V” shape of the joint (Figure 28R).

Figure 28. Ankle POCUS: Linear probe positioning to evaluate for ankle effusion (L) and normal ankle anatomy with an arrow pointing to the tibiotalar joint space (R).

  • Abnormal finding: Ankle effusion
    • Anechoic or hypoechoic fluid is seen in the tibiotalar joint space (Figure 29).

Bilateral ankle POCUS comparison with normal left tibiotalar joint and an asterisk marking anechoic effusion in the right tibiotalar joint

Figure 29. Ankle POCUS of bilateral ankles showing an effusion (*) in the right tibiotalar joint compared with the normal left side.

Figure 30. Longitudinal scanning of an ankle effusion.

POCUS of the upper extremity can assess for elbow and shoulder effusions. When an elbow effusion is identified after trauma, radiography is typically needed to further characterize a fracture.

1. Elbow

  • Positioning and probe placement: With the child’s elbow flexed to 90 degrees, place the linear transducer over the posterior distal humerus in longitudinal and transverse views to visualize the olecranon fossa and the elbow posterior fat pad (Figure 31).

Linear ultrasound probe positioning on the posterior elbow in longitudinal (L) and transverse (R) orientations with the elbow flexed to 90 degrees

Figure 31. Linear probe positioning for performing POCUS of the elbow to evaluate the elbow posterior fat pad in longitudinal (L) and transverse (R) views.

  • Normal findings
    • Identify the hyperechoic cortex of the distal humerus and the olecranon fossa.
    • The normal posterior fat pad (PFP) sits in the olecranon fossa below the continuation of the distal humeral line in the longitudinal view and below the line connecting both edges of the olecranon fossa in the transverse view. The triceps muscle can be seen above the elbow joint (Figure 32).

Normal elbow POCUS in longitudinal (L) and transverse (R) views showing the posterior fat pad (PFP) sitting below the distal humeral line in the olecranon fossa, with triceps muscle above and humerus below

Figure 32. Elbow POCUS: Normal elbow anatomy in longitudinal (L) and transverse (R) views with the posterior fat pad (PFP) located under the distal humeral line (dotted line).

Figure 33. Scanning of a normal elbow in longitudinal (L) and transverse (R) views.

  • Abnormal finding: Elbow effusion
    • Elbow US has high sensitivity and moderate specificity for fracture, so a negative scan makes fracture unlikely.
    • Sonographic findings: The posterior fat pad is elevated above the distal humeral line in the longitudinal view, and above the line connecting both sides of the olecranon fossa in the transverse view (Figure 34). Lipohemarthrosis, i.e., blood and lipid material in the posterior fat pad, may appear as hypoechoic areas within the elevated fat pad (Figure 36).
    • Clinical significance: An elevated posterior fat pad and/or lipohemarthrosis is a marker of intracapsular elbow fracture, because the posterior fat pad sits intracapsular but extra-synovial.
      • Caution: The radial neck and medial epicondyle are extracapsular, so fractures at these sites may occur without an elevated posterior fat pad.
    • Application to nursemaid elbow: Annular ligament displacement (nursemaid elbow) does not usually produce a significant effusion or lipohemarthrosis. When the diagnosis is in question, a POCUS showing a normal posterior fat pad and no lipohemarthrosis may help rule out fracture and support proceeding with closed reduction.

Elbow effusion on POCUS with elevated posterior fat pad (PFP) rising above the distal humeral line in longitudinal view (L) and above the olecranon fossa line in transverse view (R), pushing up on the triceps muscle

Figure 34. Elevated posterior fat pad in longitudinal view rising above the distal humeral line (L) and transverse view rising above the line connecting both edges of the olecranon fossa (R). In both views, the posterior fat pad pushes up on the triceps muscle.

Figure 35. Scanning of an elbow effusion with an elevated posterior fat pad in longitudinal (L) and transverse (R) views.

Elbow POCUS showing elevated posterior fat pad with lipohemarthrosis marked by yellow asterisks in longitudinal (L) and transverse (R) views

Figure 36. Elbow POCUS: Elevated posterior fat pad with lipohemarthrosis (*) in longitudinal (L) and transverse (R) views.

2. Shoulder

  • Positioning and probe placement: Place the linear transducer in the transverse view over the posterior shoulder and point the probe marker laterally (Figure 37L).
  • Normal findings
    • Identify the hyperechoic curvilinear humeral head (+/- physis) and the hyperechoic glenoid (Figure 37R). The humeral head should be located in the glenoid fossa, with the humeral head and glenoid in the same horizontal plane.
  • Abnormal finding: Shoulder effusion
    • Anechoic fluid is seen around the humeral head within the glenohumeral joint (Figure 38).

Linear ultrasound probe positioning in the transverse view over the posterior shoulder (L) and corresponding normal shoulder anatomy showing humeral head, physis, and glenoid (R)

Figure 37. Shoulder POCUS: Linear probe positioning to evaluate for shoulder effusion (L) and the corresponding ultrasound view with normal shoulder anatomy (R).

Shoulder POCUS showing a shoulder effusion with anechoic fluid (asterisk) adjacent to the humeral head, with the physis indicated by an arrow

Figure 38. Shoulder POCUS: anechoic fluid (*) adjacent to the humeral head (L) and transverse scanning of the same effusion (R).

1. Shoulder Dislocation

  • Evaluate the relative positions of the glenoid and humeral head.
  • In a normal shoulder, the humeral head and glenoid should be in approximately the same horizontal plane (Figure 37R).
  • Anterior shoulder dislocation: The humerus is farther from the transducer and thus deeper on the ultrasound screen (Figure 39).
  • Posterior shoulder dislocation: The humerus is closer to the transducer and thus higher up on the ultrasound screen.
  • POCUS can be used to confirm relocation of the humerus into the glenoid fossa after a shoulder reduction.
Transverse shoulder POCUS demonstrating an anterior shoulder dislocation, with the glenoid labeled in the upper portion of the image and the humerus labeled deeper, indicating anterior displacement of the humeral head away from the posteriorly placed probe

Figure 39. Transverse view of an anterior shoulder dislocation: humeral head dislocated anteriorly, or farther away from the probe (L) and corresponding transverse scanning (R).

2. Finger Dislocation

  • In a finger dislocation, the bone malalignment at the interphalangeal joint can be seen (Figure 40).

Finger dislocation on POCUS with the probe positioned dorsally (L) showing the dorsal aspect of the interphalangeal joint and ventrally (R) showing the malaligned phalangeal bones with LEFT PINKY label

Figure 40. Finger dislocation with probe positioned dorsally (L) and ventrally (R).

Figure 41. Scanning of a finger dislocation: dorsal view (L) and ventral view (R).

  • Ultrasound findings of osteomyelitis may precede X-ray findings by several days.
  • Sonographic findings: Disrupted or irregular bony cortex, periosteal elevation and/or abscess, and increased vascular flow (Figure 42).

Osteomyelitis of the distal femur on POCUS showing irregular bony cortex with periosteal abscess marked by asterisk (L) and color Doppler showing increased vascular flow adjacent to the periosteal abscess (R)

Figure 42. Osteomyelitis of the distal femur with irregular bony cortex and periosteal abscess (*) (L) and increased vascular flow adjacent to the periosteal abscess (R).

Figure 43. Scanning of a distal femur with osteomyelitis: longitudinal view (L) and transverse view (R).

Figure 44. Longitudinal scanning of a distal femur with osteomyelitis showing increased vascularity on color Doppler.

Bony pathology that may be missed

MSK POCUS is excellent for long-bone fractures but is less reliable for fractures at joints, epiphyses, and the small bones of the hands and feet, whose curved, irregular contours are more difficult to image. Non-displaced physeal fractures (Salter-Harris I) and fractures <1 mm may also be missed. POCUS generally focuses on the area of injury and does not image the entire bone, so distant pathology can be missed.

Additionally, for elbow evaluation, radial neck and medial epicondyle fractures are extra-capsular and may occur without an associated effusion. A normal posterior fat pad on POCUS does not exclude these fractures. If a patient has tenderness at the radial neck or medial epicondyle, obtain further imaging.

Underlying pathology that cannot be characterized

POCUS can identify the presence of pathology such as a joint effusion or bone infection, but it cannot determine the etiology (e.g., hemorrhagic vs. infectious vs. inflammatory effusion). Further work-up, such as labs, joint aspiration, or advanced imaging, is needed to characterize the underlying process.

Image sharing across systems

Sharing POCUS clips within or between institutions can be cumbersome. Where feasible, archiving images to the medical record helps preserve diagnostic context for the broader healthcare team.

There have been several systematic reviews and meta-analyses on musculoskeletal POCUS applications.

Study Application N Sensitivity Specificity Comments
Morello et al, Eur J Pediatr 2024 [3] Distal forearm fractures 23 studies, 3,484 children 92–100% 85–100% Scoping review
Hassankhani et al, Skeletal Radiol 2024 [4] Clavicle fractures 7 studies, 1,255 patients 94% 98% Pediatric subset (4 studies, 863 children): Sn 96%, Sp 94%
Zhao et al, Medicine 2019 [5] Hand fractures 7 studies, 842 patients 91% 96% Fracture prevalence 39%
Tokarski et al, J Pediatr 2018 [6] Elbow fractures 6 studies, 512 children 96% 81% Fracture prevalence 48%
Gottlieb et al, Am J Emerg Med 2019 [7] Shoulder dislocation 7 studies, 739 patients 99% 99% Dislocation prevalence 41%; associated fracture: Sn 98%, Sp 99.8%

Table 1. Key systematic reviews and meta-analyses on musculoskeletal POCUS.

Other notable studies focusing on musculoskeletal POCUS include the following.

Pediatric Distal Forearm Fracture

The BUCKLED multicenter, noninferiority, randomized trial by Snelling et al enrolled 262 children ages 5–15 years with clinically non-angulated distal forearm injuries [8]. Children were randomized to POCUS or radiography. Those in the POCUS group with a cortical break identified also received radiography and usual care; buckle fractures were managed with a splint.

Results: At 4 weeks, physical function of the affected arm was non-inferior in the POCUS group. The POCUS group also had fewer X-rays, shorter emergency department length of stay, and higher patient satisfaction. The authors emphasized that physical function at 4 weeks is an important, real-world clinical outcome.

Joint Effusions

Adhikari and Blaivas compared POCUS with physical examination for the diagnosis of joint effusions [9]. They enrolled 54 adult patients with joint pain, erythema, and swelling.

Results: POCUS was more sensitive and accurate than physical examination. POCUS altered emergency department management in 65% of patients, either by avoiding an unnecessary joint aspiration or by identifying a clinically occult effusion.

Pediatric Hip Effusion

Jones et al conducted a multicenter prospective diagnostic study in children <18 years requiring radiology-performed hip ultrasound, comparing hip POCUS with the radiology study as the reference standard [10]. 161 children were enrolled by 18 PEM physicians, with 3 high-volume operators contributing 62% of cases.

Results: POCUS had an overall sensitivity of 94% and specificity of 98%. Among high-volume operators, sensitivity was 98% (specificity 98%); among low-volume operators, sensitivity was 83% (specificity 97%).

Case Resolution

A musculoskeletal POCUS of the left knee with a linear, high-frequency probe demonstrated a joint effusion in the suprapatellar bursa with internal septations (Figures 45 and 46).

Pediatric left knee POCUS composite showing suprapatellar joint effusion (L) and effusion with internal septations (R)

Figure 45. Left knee POCUS demonstrating a joint effusion in the suprapatellar bursa (L) and internal septations within the effusion (R).

Figure 46. Longitudinal scan of the left knee showing the joint effusion with internal septations.

Initial laboratory studies showed a white blood cell count of 10 × 109/L, ESR 69 mm/hr, and CRP 32 mg/L. Knee radiographs were negative for fracture. Orthopedics performed an arthrocentesis that yielded synovial fluid with 52,000 white blood cells/µL, raising concern for septic arthritis.

The patient was admitted, started on intravenous antibiotics, and taken to the operating room for incision, drainage, and washout. Joint fluid cultures returned negative, but Lyme serologies returned positive. She was transitioned to a 28-day course of doxycycline for Lyme arthritis.

Read more from this series → PEM POCUS Series

References

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  2. Wilson C. Suprapatellar bursitis: causes, symptoms, treatment & recovery. Knee Pain Explained. Published June 2, 2024. Accessed May 23, 2026. https://www.knee-pain-explained.com/suprapatellar-bursitis.html
  3. Morello R, Mariani F, Snelling PJ, Buonsenso D. Point-of-care ultrasound for the diagnosis of distal forearm fractures in children and adolescents: a scoping review. Eur J Pediatr. 2024;184(1):19. doi:10.1007/s00431-024-05877-w. PMID: 39548004
  4. Hassankhani A, Amoukhteh M, Jannatdoust P, Valizadeh P, Gholamrezanezhad A. A systematic review and meta-analysis on the diagnostic utility of ultrasound for clavicle fractures. Skeletal Radiol. 2024;53(2):307-318. doi:10.1007/s00256-023-04396-3. PMID: 37433884
  5. Zhao W, Wang G, Chen B, et al. The value of ultrasound for detecting hand fractures: a meta-analysis. Medicine (Baltimore). 2019;98(44):e17823. doi:10.1097/MD.0000000000017823. PMID: 31689869
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  8. Snelling PJ, Jones P, Bade D, et al; BUCKLED Trial Group. Ultrasonography or radiography for suspected pediatric distal forearm fractures. N Engl J Med. 2023;388(22):2049-2057. doi:10.1056/NEJMoa2213883. PMID: 37256975
  9. Adhikari S, Blaivas M. Utility of bedside sonography to distinguish soft tissue abnormalities from joint effusions in the emergency department. J Ultrasound Med. 2010;29(4):519-526. doi:10.7863/jum.2010.29.4.519. PMID: 20375371
  10. Jones RM, Malia L, Snelling PJ, et al. Diagnostic accuracy of point-of-care ultrasound for hip effusion: a multicenter diagnostic study. Ann Emerg Med. 2025;86(6):566-575. doi:10.1016/j.annemergmed.2025.04.033. PMID: 40481828

PEM POCUS Series: Pediatric Lung Ultrasound

PEM POCUS fascia iliaca block

Read this tutorial on the use of point of care ultrasonography (POCUS) for pediatric lung ultrasound. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.

Module Goals

  1. List indications for performing a pediatric lung point-of-care ultrasound (POCUS).
  2. Describe the technique for performing lung POCUS.
  3. Recognize anatomical landmarks and artifacts related to lung POCUS.
  4. Interpret signs of a consolidation, interstitial fluid, effusion, and pneumothorax on POCUS.
  5. Describe the limitations of lung POCUS.

Child with Cough and Fever: Case Introduction

A 6-year-old boy presents to the emergency department complaining of cough for 3 days and fever for the last day. His fever was 103°F this morning and he received ibuprofen. He has also had abdominal and back pain. He was seen at the emergency department earlier in the day where he had a chest X-ray 6 hours prior that was interpreted as negative for consolidation and bloodwork including a complete blood count and comprehensive metabolic panel that were within normal limits. He presents with persistent cough and fever and now has increased work of breathing.

On arrival, his vital signs are:

Vital Sign Finding
Temperature 99.7 F
Heart Rate 138 bpm
Blood Pressure 102/61
Respiratory Rate 32
Oxygen Saturation (room air) 100%

He is well appearing but has increased work of breathing. His lungs have decreased breath sounds and crackles over the left lung base. No wheezes are appreciated. He has mild subcostal retractions. His abdomen is soft, non-tender, and non-distended. His back is non-tender to palpation. He has normal HEENT, neck, and cardiac examinations, with the exception of tachycardia as above.

Given his presenting signs and symptoms in the setting of a recent chest X-ray that was interpreted as normal, you decide to perform a lung point-of-care ultrasound (POCUS) examination.

Lung POCUS can be performed for a wide range of cardiorespiratory complaints including cough, fever, difficulty breathing, chest pain, hypoxia, and chest trauma. It can also facilitate early diagnosis, allowing for appropriate management. Children are excellent candidates for lung POCUS as they have thinner chest walls and smaller thoracic widths than adults.

Background

The lungs were traditionally considered poorly accessible to ultrasound, as ultrasound waves cannot penetrate air-filled structures; however, lung POCUS relies on the interpretation of patterns of artifacts to evaluate the normal, air-filled lungs.

When there is lung pathology, the consolidation or fluid allows for direct visualization of the pathology with lung POCUS and replaces the air artifacts. Fluid in a consolidation or effusion is easily visualized with ultrasound if the fluid has direct contact with the pleural surface. As lung POCUS will only visualize the lung under the probe, it is essential to completely evaluate the lungs anteriorly, laterally, and posteriorly to avoid missing pathology.

Technique

Positioning and Probe

lung POCUS comfortable positioning child

Figure 1: Younger children can sit in their parent’s lap and give a hug for lateral and posterior lung scanning.

  • The patient should be in a position of comfort: supine, sitting, or in parent’s lap (Figure 1).
    • Warm gel helps with the child’s comfort.
    • Distractions such as a toy, book, or phone/tablet can also help ease anxiety.
  • Use a linear high frequency probe. If increased depth is needed, such as in the evaluation for effusion, a curvilinear or phased array probe may also be used.

 

Scanning Protocols

There are different protocols to scan the lung depending on the purpose of the evaluation. For example, in pneumothorax, we focus on the anterior chest where air rises in a supine patient, and for the extended Focused Assessment with Sonography (eFAST) exam, we focus on more dependent areas where pleural fluid or blood collects. Below we discuss the complete lung exam which is often used in evaluating for pneumonia.

Lung POCUS anatomy 6-zone scan area

Figure 2: The 6-zone lung scanning protocol includes anterior, lateral, and posterior lung fields bilaterally.

  • A 6-zone lung ultrasound protocol is used for a complete lung examination (Figure 2):
    • Anterior lungs bilaterally are scanned in the mid-clavicular line from the apex to the base of the lungs and diaphragm.
    • Lateral lungs bilaterally are scanned in the mid-axillary line from the apex to the base of the lungs and diaphragm.
    • Posterior lungs bilaterally are scanned medial to the scapulae and lateral to the vertebral bodies from the apex to the base of the lungs and diaphragm.
  • Place the probe longitudinally, perpendicular to the ribs, with the probe marker towards the patient’s head. Identify anatomical landmarks on ultrasound (Figure 3, Video 1).
Lung POCUS A lines normal child

Figure 3: Normal lung with A-lines in longitudinal (left) and transverse (right) orientations

 

Video 1: Normal lung POCUS in longitudinal orientation

 

Video 2: Normal lung POCUS in transverse orientation

Normal Lung Findings

  1. Ribs: Hyperechoic, curvilinear structure with posterior acoustic shadowing
  2. Pleural line: Hyperechoic line immediately deep to the ribs
    • Lung sliding sign: Visceral and parietal pleural are juxtaposed and sliding against each other with respirations, giving the pleural line a shimmering or “ants marching on a log” appearance. For additional examples, see the PEM POCUS Endotracheal Intubation Confirmation article, specifically in Section 2 – Indirect Confirmation: Visualize Bilateral Lung Sliding.
  3. Lungs filled with air: Visualized on POCUS as horizontal A-lines, which are a reverberation artifact of the pleural line. The pleural line is reflected as the ultrasound beams bounce back and forth between the probe and the highly reflective pleural line, and therefore the distance between A-lines is the same as the distance between the probe and the pleural line (Figure 4).
Lung POCUS A lines reverberation normal

Figure 4: Reverberation artifact and A-lines. The probe sends out ultrasound waves that bounce back and forth between the highly reflective pleural line and the probe (leftmost 3 arrows). The ultrasound machine then interprets these signals as A-lines equidistant from the pleural line (rightmost 3 arrows).

Lung POCUS pulmonary consolidation

Figure 5: Pneumonia with sonographic hepatization, air bronchograms, and irregular pleural line

 

Video 3: Lung POCUS showing a pneumonia

 

Consolidation will appear as a subpleural, hypoechoic, irregularly shaped area, which will move with respirations. It can have the following findings on lung POCUS:

  • Hepatization refers to the homogenous, soft tissue echotexture due to fluid in the lung.
  • Shred sign refers to the irregular borders of the non-pleural edge of a pneumonia that is not translobar and thus adjacent to normal lung.
  • Pleural line irregularities refer to the hypoechoic or fragmented pleural line at the consolidation.
  • Hyperechoic air bronchograms are air in the bronchioles (white dots or branches) surrounded by hypoechoic (dark), fluid-filled lung (Figure 5 and Video 3).
Lung POCUS B lines waterfall

Figure 6: Lung POCUS showing B-lines (A) and a confluence of B-lines, known as the waterfall sign (B)

Video 4: Lung POCUS showing a confluence of B-lines (waterfall sign)

B-lines represent interstitial fluid and may arise from viral infection, pulmonary edema, or acute respiratory distress syndrome (ARDS).

  • POCUS appearance:
    • Ring-down artifacts that arise from the pleural line and extend to the bottom of the screen (Figure 6A). They move with lung sliding and erase A-lines at their intersection.
    • More than 3 B-lines in an intercostal space has been considered abnormal in the adult population. However it may not always be feasible to accurately count the number of B-lines.
    • The distribution of B-lines may help differentiate etiologies, with focal B-lines in pneumonia or atelectasis, and diffuse B-lines in pulmonary edema or ARDS.
  • Waterfall sign: A confluence of B-lines (Figure 6B and Video 4)
POCUS lung subpleural consolidation

Figure 7: Lung POCUS with subpleural consolidation

Video 5: Lung POCUS with subpleural consolidation

Subpleural consolidations are small hypoechoic or tissue-like structures with pleural line abnormalities and blurred margins (Figure 7 and Video 5). They measure <1 cm and are usually seen with a viral process.

Lung POCUS pleural effusion

Figure 8: Pleural effusion with linear probe (A) and phased array probe for increased depth (B).

Video 6: Lung POCUS with pleural effusion using linear probe

A pleural effusion is visualized as anechoic (black) fluid between the chest wall and lung or between the diaphragm and lung (Figure 8 and Video 6).

  • Scan the lateral chest in the posterior axillary line in the supine patient, as fluid is dependent and will accumulate posteriorly.
  • The pleural effusion can be fluid in an infectious process or blood in the setting of trauma.

Absent Lung Sliding

Video 7: Lung POCUS showing a pneumothorax with absent lung sliding

In pneumothorax, there is air between the visceral and parietal pleural, so there will be no lung sliding visualized on lung POCUS.

  • Scan for a pneumothorax in the anterior chest in the 2nd-4th intercostal space in the mid-clavicular line in a supine patient, as air will rise to the highest point in the chest.
  • The pleural line will appear as a static, hyperechoic line (Video 7).
  • There will be A-lines visualized, but no B-lines.
    • Pro Tip: The presence of B-lines is highly sensitive against the presence of a pneumothorax in that location.

 

Lung Point

Video 8: Lung POCUS with evidence of a lung point

Lung point, when seen, is the edge of the pneumothorax, where regular lung sliding occurs adjacent to absent lung sliding (Video 8).

  • Lung point is 100% specific for pneumothorax, but it may not be visualize d for a large pneumothorax with lung collapse.

 

Motion (M) Mode

Figure 9: Lung POCUS showing a normal lung with the seashore sign (A) and a pneumothorax with the barcode sign (B)

M-mode may also be used to evaluate for pneumothorax.

  • Normal lung: There will be the seashore sign, with a granular pattern representing aerated, moving lung below the pleural line (Figure 9a).
  • Pneumothorax: There will be a barcode or stratosphere sign, with no aeration or movement below the pleural line (Figure 9b).

Additional examples can be found in the PEM POCUS: Endotracheal Tube Confirmation article in Section 2 – Indirect Confirmation: Visualize Bilateral Lung Sliding.

lung abscess

Figure 10: Lung abscess with adjacent lung consolidation and pleural effusion

 

Lung abscess may also be evaluated by lung POCUS and will have a hypoechoic fluid collection (Figure 10).

  • Consolidated lung and pleural effusion are also commonly seen.
  • Lung ultrasound is more accurate than chest X-ray at evaluating lung abscess.

Lung pathology may be missed without a complete lung POCUS scanning protocol, as you will only see pathology located directly under the probe. The lung POCUS is also operator-dependent, and it has a steep learning curve.

False Negative:

  • POCUS can’t visualize a centrally located pneumonia not extending to the pleural surface. A lung consolidation needs to extend to the pleural surface to be visualized on lung POCUS.
  • However, a study in adult patients showed that 99% of lung consolidations extend to the pleura [1]. Thus, in children with smaller lung mass, most consolidations likely will be detected by lung POCUS.

False Positives:

Left Lower Chest

  • Caution is needed at the left lower chest, as the spleen and air in the stomach can be misinterpreted as consolidation (Figure 11).
  • Locate the diaphragm in the left lower chest to be sure you are evaluating lung above the diaphragm.
stomach spleen

Figure 11: The spleen and the stomach with air may be misinterpreted as consolidation.

Thymus

  • In younger children, the thymus may be misinterpreted as a consolidation.
  • The thymus will be adjacent to the heart, have regular echotexture, no air bronchograms, and regular borders (Figure 12).
thymus

Figure 12: Thymus (*) located adjacent to the heart

 

There have been multiple studies of lung POCUS identifying pneumonia in children, and several meta-analyses have been published [2-4]. Table 1 summarizes these studies, showing an overall high accuracy for lung POCUS diagnosis of pneumonia in children.

Study N Sensitivity Specificity Comments
Pereda et al., Pediatrics 2015 8 studies; 765 patients

96%

93%

Evidence supports lung POCUS as an alternative for diagnosis of pneumonia in children.
Balk et al., Pediatr Pulmonol 2018 12 studies; 1510 patients

96%

95%

Lung POCUS had significantly better sensitivity than chest X-ray, which had a sensitivity of 87%.
Tsou et al., Acad Emerg Med 2019 25 studies; 3353 patients

94%

92%

Significant difference in accuracy between novice and advanced sonographers.
Table 1. Meta-analyses of lung POCUS for diagnosis of pneumonia in children

1. Decreased radiation and length of stay

  • A randomized controlled trial comparing lung POCUS to chest X-ray for diagnosis of pneumonia showed a 39% reduction in chest X-ray utilization and a decreased emergency department length of stay from 180 to 132 minutes in the patients receiving only lung POCUS with no cases of missed pneumonia [5].

2. Best view for pneumonia

  • A study looking at lung consolidation locations in children with pneumonia found that 96% of pneumonias were detected by the transverse view, compared to 86% in the longitudinal view.
  • The authors concluded that the transverse orientation detects more pneumonia than the longitudinal view, and that omission of either orientation or any lung zone may miss pneumonia [6].

3. Pneumothorax: POCUS is better

  • A meta-analysis of chest X-ray vs ultrasound for diagnosis of pneumothorax showed that ultrasound had a sensitivity of 88% and specificity of 99% compared to sensitivity of 52% and specificity of 100% for chest X-ray. Furthermore, lung POCUS performed specifically by non-radiologist clinicians had a sensitivity of 89% and specificity of 99% [7].

Case Resolution

The patient’s chest X-ray from earlier in the day was interpreted by the pediatric radiologist as negative for consolidation or other pulmonary pathology. You performed a lung POCUS with a linear, high-frequency probe and observed the following:

Video 9: A lung POCUS of the case patient’s left lower lung (affected side)

Though this child with cough, fever, focal lung findings, and respiratory distress had a negative chest X-ray performed 6 hours earlier, your POCUS evaluation identified a left lower lobe pneumonia which helped you make your diagnosis and start the appropriate treatment.

ED Course

The patient received antibiotics for pneumonia. His work of breathing increased during his emergency department visit, and he was started on high flow nasal cannula at 30 L/min with improvement in his respiratory status. He was admitted to the pediatric intensive care unit. He had a repeat chest X-ray 12 hours later that was interpreted by the pediatric radiologist as having new pleural and parenchymal changes in the left hemithorax with questionable pneumonia. He continued antibiotics, and his repeat X-ray 48 hours later showed a clear left lower lobe consolidation with pleural effusion.

 


Learn More…

References

  1. Lichtenstein DA, Lascols N, Mezière G, Gepner A. Ultrasound diagnosis of alveolar consolidation in the critically ill. Intensive Care Med. 2004 Feb;30(2):276-281. PMID: 14722643
  2. Pereda MA, Chavez MA, Hooper-Miele CC, et al. Lung ultrasound for the diagnosis of pneumonia in children: a meta-analysis. Pediatrics. 2015 Apr;135(4):714-22. PMID: 25780071
  3. Balk DS, Lee C, Schafer J, et al. Lung ultrasound compared to chest X-ray for diagnosis of pediatric pneumonia: A meta-analysis. Pediatr Pulmonol. 2018 Aug;53(8):1130-1139. PMID: 29696826
  4. Tsou PY, Chen KP, Wang YH, et al. Diagnostic Accuracy of Lung Ultrasound Performed by Novice Versus Advanced Sonographers for Pneumonia in Children: A Systematic Review and Meta-analysis. Acad Emerg Med. 2019 Sep;26(9):1074-1088. PMID: 31211896
  5. Jones BP, Tay ET, Elikashvili I, et al. Feasibility and Safety of Substituting Lung Ultrasonography for Chest Radiography When Diagnosing Pneumonia in Children: A Randomized Controlled Trial. Chest. 2016 Jul;150(1):131-8. PMID: 26923626
  6. Milliner BHA, Tsung JW. Lung Consolidation Locations for Optimal Lung Ultrasound Scanning in Diagnosing Pediatric Pneumonia. J Ultrasound Med. 2017 Nov;36(11):2325-2328. PMID: 28586113
  7. Ding W, Shen Y, Yang J, He X, Zhang M. Diagnosis of pneumothorax by radiography and ultrasonography: a meta-analysis. Chest. 2011 Oct;140(4):859-866. PMID: 21546439

Additional Reading

  • Rizvi MB, Rabiner JE. Pediatric Point-of-Care Lung Ultrasonography: A Narrative Review. West J Emerg Med. 2022 Jun 5;23(4):497-504. PMID: 35980421
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