Microvascular flow imaging in musculoskeletal ultrasound: from technical innovation to clinical integration.

Recent advances in Doppler ultrasound have led to the development of microvascular flow imaging, a technique designed to overcome the limitations of color and Power Doppler in detecting slow, small-vessel flow. This narrative review summarizes the technical foundations, clinical applications, and emerging perspectives of microvascular technologies in musculoskeletal ultrasound, emphasizing their role as a bridge between morphological and functional imaging. Microvascular flow imaging employs spatiotemporal clutter-suppression algorithms and high-frame-rate acquisition to visualize low-velocity blood flow within capillaries smaller than 100 µm, without the need for contrast agents. The method enhances detection of microvascularity in tendons, synovium, and peripheral nerves, providing early indicators of inflammatory or degenerative activity. Proprietary vendor implementations share the same physical principles but differ in algorithmic filtering and signal rendering. Clinically, microvascular flow imaging has demonstrated superior sensitivity compared with Power Doppler for detecting subclinical synovitis, assessing tendinopathies, and evaluating entrapment neuropathies, offering both quantitative and prognostic insights. Although microvascular flow imaging improves diagnostic sensitivity and supports dynamic, contrast-free assessment of tissue perfusion, its routine implementation remains limited by the absence of standardized acquisition protocols, validated quantitative metrics, and inter-vendor harmonization. Ongoing research into AI-based vascular quantification and portable point-of-care systems may enhance reproducibility, accessibility, and integration into everyday musculoskeletal imaging. Overall, microvascular flow imaging represents a pivotal step toward functional musculoskeletal ultrasound, with expanding diagnostic, prognostic, and theranostic potential.