The research, led by Sandra Hansmann of the University Children’s Hospital Tübingen together with Johannes Roth of the Children’s Hospital of Central Switzerland and the University of Lucerne, focused on the entheses, the specialized zones where tendons and ligaments anchor into bone. These structures are far more than simple attachment points. They comprise tendon fibers, fibrocartilage, and associated bursae, forming what researchers call the enthesis organ. In adults, enthesitis, or inflammation at these sites, is a hallmark of spondyloarthritis and psoriatic arthritis. In children, it defines enthesitis-related arthritis, a category of juvenile idiopathic arthritis associated with substantial disease burden and unfavorable long-term outcomes.

While musculoskeletal ultrasound has become a cornerstone of pediatric rheumatology, and age-related normative data exist for joints, comparable data for entheses have remained sparse. Internationally agreed ultrasound definitions for enthesitis exist only for adults. Because children’s bodies are actively growing, with tendons thickening and cartilage receding as ossification progresses, adult criteria cannot simply be transplanted to pediatric patients. Blood flow detected by Doppler ultrasound, which in an adult strongly suggests inflammation, is frequently a normal finding in growing children whose tissues have high metabolic demands.

To establish a reliable baseline, the team recruited 79 healthy children and adolescents aged 6 to 16 years, the typical age of onset for juvenile enthesitis-related arthritis. Participants with musculoskeletal symptoms, inflammatory diseases, or trauma history were excluded. Each child underwent standardized B-mode and power Doppler ultrasonography of ten tendon insertions at the dominant hip, knee, and ankle, covering sites that are frequently affected in juvenile disease but had been poorly characterized before, including the sartorius and rectus femoris insertions at the pelvis, the gluteus minimus and medius attachments at the greater trochanter, the tibialis posterior and peroneus brevis insertions at the ankle, and the quadriceps, patellar, and Achilles tendons at the knee and heel.

The technical protocol was rigorous. Examinations were performed with an Aplio i800 machine equipped with a high-frequency linear transducer, using low-flow Doppler settings with a pulse repetition frequency of 500 to 750 Hz and low wall filters to maximize sensitivity to slow blood flow. Heel-toe maneuvers of the probe corrected for anisotropy, the artifact that can artificially darken tendon fibers when the ultrasound beam strikes them at an angle. Generous amounts of gel prevented compression of small vessels. Measurements of entheseal thickness were taken at defined positions where the enthesis contacts the bone, orthogonal to the tendon fibers, and every image had to contain identifiable anatomic landmarks to confirm correct positioning.

The results were striking in their consistency. Of 790 entheses scanned, 782 yielded evaluable images, and every single one showed a normal fibrillar pattern on B-mode imaging. No hypoechoic regions, enthesophytes, calcifications, bone erosions, or signs of traction apophysitis such as Sever’s, Osgood-Schlatter, or Sinding-Larsen-Johansson disease appeared in any participant. This stands in sharp contrast to healthy adults, in whom enthesophytes and cortical irregularities are common cumulative wear-related findings. In children, the authors argue, such structural abnormalities appear to be virtually absent during normal growth, making them highly specific indicators of genuine pathology when they do occur.

Reliability measurements reinforced confidence in the technique. Intraclass correlation coefficients for entheseal thickness ranged from 0.84 to 0.99 between observers and from 0.91 to 0.99 within the same observer, values considered high to excellent. Weighted Cohen’s kappa statistics for Doppler grading indicated substantial to perfect agreement. Entheseal thickness, which ranged from 1.0 to 15.2 millimeters depending on site and age, correlated strongly with age, with Pearson coefficients between 0.65 and 0.90 across locations. Notably, hierarchical regression showed that age outperformed height, weight, pubertal stage, sex, and physical activity as the primary determinant of thickness, and no significant sex-specific differences emerged at most sites, suggesting that sexual dimorphism in entheseal morphology has not yet been established in this age range.

The Doppler findings carry the greatest clinical implications. Minor power Doppler activity was detected in 1 to 44 percent of entheses within 2 millimeters of the insertion, rising to 2 to 68 percent within 5 millimeters. Signals clustered at specific locations: the proximal sartorius insertion showed vascularity in 67.5 percent of participants, and the knee entheses in 30 to 40 percent, while the gluteal and peroneus brevis entheses remained largely avascular, with more than 94 percent of scans showing no signal. Physical activity emerged as a correlate for vascularity at the sartorius and distal quadriceps sites, and body weight for the Achilles, but most sites showed no demographic or lifestyle dependencies at all, supporting the interpretation that these signals reflect the physiological vascularity of the developing enthesis organ rather than inflammation.

The authors conclude that pathological Doppler signals in children may require accompanying B-mode abnormalities to be considered meaningful. They propose that a diagnosis of enthesitis on pediatric ultrasound should rest on a combination of morphological abnormalities, age-standardized thickening, and vascularity beyond physiological findings. This multi-parameter approach could reduce overdiagnosis of juvenile idiopathic arthritis, spare children unnecessary treatment, and provide the foundation for internationally agreed definitions and scoring systems for pediatric enthesitis, which currently do not exist.

As a single-center pilot study with a modest sample size, the work requires validation in larger prospective cohorts, and the reliance on still images rather than real-time dynamic assessment represents a limitation. Bilateral measurements in a subset of 19 participants also revealed significant side-to-side differences at the gluteus medius, distal quadriceps, and tibialis posterior entheses, a nuance clinicians will need to consider. Nevertheless, the examination protocol proved highly feasible and well tolerated even in young children, and its flexible design allows clinicians to focus on specific entheses in routine practice. By charting the normal landscape of the growing enthesis, the study gives pediatric rheumatologists, for the first time, a credible map of where normal ends and disease begins.

Subject of Research: Normative B-mode and power Doppler ultrasound characteristics of lower extremity entheses in healthy children and adolescents

Article Title: Musculoskeletal ultrasonography of lower extremity entheses in children and adolescents – a pilot study of normal B-mode and Doppler characteristics

Article References: Hansmann, S., & Roth, J. (2026). Musculoskeletal ultrasonography of lower extremity entheses in children and adolescents – a pilot study of normal B-mode and Doppler characteristics. Pediatric Radiology. https://doi.org/10.1007/s00247-026-06784-y

Image Credits: AI Generated

DOI: 10.1007/s00247-026-06784-y

Keywords: musculoskeletal ultrasound, entheses, pediatric rheumatology, juvenile idiopathic arthritis, enthesitis, power Doppler, B-mode ultrasonography, healthy children, lower extremity, normative data, Pediatric Radiology, tendon insertion