80-year-old male patient brought in by ambulance for a witnessed fall. A cervical collar was placed by EMS because of midline neck pain. The patient is neurologically intact. A CT of the cervical spine was obtained and is shown above (Case courtesy of Dr. Talal F M Abdullah, Radiopaedia.org, rID: 58030).
A 65-year-old farmer presents to the ED after his ankle was run over by a piece of farm equipment in the field. His x-ray is shown above (Figure 1: Case courtesy of Dr. Oyedepo Victor Olufemi, radiopaedia.org) He also has an associated soft tissue injury overlying the area that is grossly contaminated with mud and manure. (more…)
Read this tutorial on the use of point of care ultrasonography (POCUS) for pediatric hip effusion. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.
Sarah is a 4-year-old girl who comes into the emergency department complaining of a limp for the last day. She had an upper respiratory infection which started a week ago for which she had been taking acetaminophen and ibuprofen with her last dose of either being 2 days ago. Those symptoms have improved. Yesterday, she started complaining of diffuse right leg pain primarily at her hip, thigh, and knee. Today, her parents noted she was walking with a limp.
On arrival, her vital signs are:
| Vital Sign | Finding |
|---|---|
| Temperature | 100.1F |
| Heart rate | 100 bpm |
| Blood pressure | 97/50 |
| Respiratory rate | 19 |
| Oxygen saturation (room air) | 100% |
She is well appearing and walks with an antalgic gait favoring the left leg. She has a normal HEENT, neck, cardiac, respiratory, abdominal, and back examination. She points to her right anterior thigh when you ask her where her pain is. She has limited range of motion with internal and external rotation of her right hip and complains of pain. She cries when you palpate any part of her leg, but is able to range her knee, ankle, and foot fully. She has 2+ dorsalis pedis and posterior tibialis pulses and intact sensation to light touch throughout.
Given her pain with range of motion at her hip, you order a hip radiograph, but while waiting for it, decide to perform a hip point of care ultrasound (POCUS) examination.
It can be difficult for children to locate the exact area of pain and often hip pain can present with referred knee and thigh pain. A thorough physical examination along with hip POCUS can help localize the area of discomfort. When we use POCUS to evaluate the hip, we are primarily looking for a joint effusion in the synovial space. This is best visualized anterior to the femoral neck.
A hip effusion will appear anechoic (black) in the synovial space anterior to the femoral neck (anterior synovial recess). Measure the distance between the anterior surface of the femoral neck and the posterior surface of the iliopsoas muscle. Examples are illustrated in figures 5 and 6.
There have been different methods used to assess if an effusion is present including:1,2
Note that hip POCUS does not tell you the cause of an effusion but rather only whether an effusion is present or not. Effusions can result from infectious, inflammatory, and traumatic etiologies, and thus it is important to take into account the context of the patient’s presentation.
There have been multiple case reports of hip POCUS identifying hip effusions in children with fractures, septic joints, and in the work-up of children with limps [1–4]. There are limited studies examining the accuracy of hip POCUS compared to radiology-performed ultrasounds in children. The studies that exist show high sensitivity and specificity when hip POCUS is performed by pediatric emergency medicine (PEM) physicians (Table 1).
Additional studies have explored the development of hip effusion clinical decision-making tools to support POCUS in the diagnosis of transient synovitis and differentiate it from other causes of non-traumatic arthritis in patients with a hip effusion, including septic arthritis, Lyme arthritis, and osteomyelitis [5]. For example, one retrospective pilot study found that the combination of POCUS performed by PEM physicians and a clinical decision rule could correctly rule in transient synovitis in 63 of 67 patients with a hip effusion [6].
The use of POCUS in the ED has also been associated with cost savings and greater clinical efficiency. In pediatric patients, hip POCUS has demonstrated potential cost-saving benefits compared with radiology-performed ultrasound. One Australian economic evaluation estimated annual savings of approximately AU$35,800 (about US$25,000), mainly by shortening the time children spent in an ED bed waiting for an ultrasound [7]. Additionally, in a case series of 10 children with septic arthritis of the hip, POCUS-guided hip aspiration by a PEM-trained physician was associated with a shorter time to antibiotic administration [1].
Although standardized training requirements for hip effusion POCUS in pediatric patients have not been established, scanning accuracy appears to be influenced by operator experience and confidence. As illustrated in Table 1, sensitivity and specificity were higher among physicians who had performed more hip POCUS scans and among those with greater confidence in their ultrasound skills [8,9,11]. These findings highlight the importance of continued practice and experience in developing proficiency in hip POCUS, ultimately improving diagnostic accuracy and supporting timely clinical decision-making. So, make sure to keep scanning!
| Study | N | Sensitivity | Specificity | Comments |
|---|---|---|---|---|
| Vieira et al., Ann Emerg Med, 2010 [8] | 28 | 85% | 93% | If the pediatric emergency physician had a high confidence in ultrasound accuracy, the sensitivity increased to 90% and specificity to 100%. |
| Cruz et al., Am J Emerg Med, 2018 [9] | 516 | 85% | 98% | For each additional hip POCUS performed, the odds of an accurate scan increased by 2.4%. |
| Katz-Dana et al., CJEM, 2024 [10] | 95 | 89.8% | 91.3% | Strong positive LR of 10.33 and negative LR of 0.11 for PEM physician-performed POCUS. |
| Jones et al., Ann Emerg Med, 2025 [11] | 161 (322 hips) | 89.3% | 99.2% | For the 3 high-volume pediatric emergency physicians, sensitivity and specificity increased to 98.1% and 97.8%, respectively. Sensitivity and specificity are per hip. |
The patient’s hip plain film radiographs are unremarkable. You decide to incorporate hip POCUS to your evaluation. You place a linear, high-frequency transducer and visualize the patient’s bilateral hips. You observe the following:
Though the child complained of hip, knee, and thigh pain, your POCUS evaluation identifies a right hip effusion which helps you narrow the location of her pain.
The patient’s labs result, and she has reassuring labs, which include a serum WBC 8.3 x109/L and ESR 34 mm/hr. The patient receives ibuprofen during her visit and within 1 hour is able to walk without a significant limp and states she feels better. The patient’s family notes they have spent the last few weeks of summer in a Lyme-endemic region, and so you send off Lyme titers.
Given the resolution of limp, lack of fever, and reassuring lab values, you do not believe the patient has a septic joint. Her effusion is more likely the result of a transient synovitis. You recommend close pediatrician follow-up.
At her pediatrician clinic visit 1 week later, her Lyme titers return negative, and the patient continues to be limp-free.
The PEM POCUS series was created by the UCSF Division of Pediatric Emergency Medicine to help advance pediatric care by the thoughtful use of bedside ultrasonography.
Read other PEM POCUS tutorials. Learn more about bedside ultrasonography on the ALiEM Ultrasound for the Win series.
Figure 1. Case courtesy of Dr Andrew Dixon, Radiopaedia.org, rID: 9601
Figure 1. Case courtesy of Dr Hani Makky ALSALAM, Radiopaedia.org, rID: 8720
Stress fracture at the distal tibial metaphysis – note the faint sclerotic line at the tibial metaphysis (Figure 2).
Figure 2. Arrows identifying the stress fracture. Case courtesy of Dr. Hani Makky Al Salam, Radiopaedia.org, rID: 8720
When coupled with the amenorrhea, consider the female athlete triad.
Plain film ankle views should be obtained. If a stress fracture is acute, sensitivity on plain films can be as low as 10% [6]. MRI can be performed outpatient with a sensitivity approaching 100% [4,5,7,8]. A pregnancy test should be performed as well given the amenorrhea. A standard workup for amenorrhea should be performed as an outpatient. Inquire about eating habits and anxiety/depression.
The three components of the female triad are on a spectrum of severity in the disruption of bone mineral density/osteoporosis, menstrual dysfunction/dysmenorrhea, and low energy with or without an eating disorder [1,9-11]. Patients will have a degree of dysfunction of all three components.
Stress fracture treatment included rest and analgesics. Immobilization is not necessary, but refraining from activity which exacerbates pain is crucial. NSAIDs may be used for pain control [5,7]. Female athlete triad is multifactorial and outpatient follow up should be ensured. Referral to adolescent medicine, sports medicine, or close primary care follow up is important.
Check out ALiEM’s SplintER Series to brush up on other can’t miss diagnoses of ankle pain.
Have you ever been working a shift at 3 am and wondered, “Am I missing something? I’ll just splint and instruct the patient to follow up with their PCP in 1 week.” This can be a reasonable approach, especially if you’re concerned there could be a fracture. But we can do better. Enter the “Can’t Miss” series: a series organized by body part that will help identify common and catastrophic injuries. This list is not meant to be a comprehensive review of each body part, but rather to highlight and improve your sensitivity for these potentially catastrophic injuries. We reviewed the approach to the pediatric elbow previously. Now, the “Can’t Miss” pediatric elbow injuries. (more…)
