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

BACKGROUND: Musculoskeletal ultrasonography is an important imaging modality in children. Features of arthritis are well defined and age-related normative data exist. Data on entheses are limited with no consensus on definition of pathology. OBJECTIVES: The aim of this pilot study was to evaluate entheseal thickness, echotexture, and presence of vascularity in healthy children and adolescents as a prerequisite for distinction from pathology. MATERIALS AND METHODS: Children and adolescents without musculoskeletal conditions underwent standardized B-mode and power Doppler ultrasonography of the dominant hip, knee, and ankle entheses. Entheseal thickness, echotexture, and vascularity were assessed, alongside demographic, puberty, and physical activity data. Statistical analysis included intraclass correlation coefficients, single regression, and t-tests. RESULTS: Seventy-nine healthy participants (mean age 10.5 years; 48% female) were included. All 782 evaluated entheses showed normal B-mode echotexture. Inter- and intraobserver reliability was high to excellent, with intraclass correlation coefficient values ranging from 0.84-0.99 and 0.91-0.99, respectively. Entheseal thickness correlated significantly with age (r = 0.65-0.90), lacking sex-specific differences at most sites. Minor power Doppler activity was detected in 1-44% of entheses within 2 mm of the insertion, increasing to 2-68% within 5 mm. Doppler signals were most frequent at proximal sartorius and knee entheses. CONCLUSION: Entheseal thickness correlates with age, but sex differences are minimal. Mild signals are common at the sartorius, quadriceps, and Achilles entheses with normal B-mode findings. Pathologic Doppler may require accompanying B-mode abnormalities. These data broaden the base for ultrasonography of pediatric entheses and facilitate differentiation of pathology from normal findings.