Sono-Anatomy and Histology of the Deep Fasciae in the Upper Limb.

The deep fascia of the upper limb represents a pivotal anatomical structure essential for effective force transmission, dynamic compartmentalization and musculoskeletal stability. Its composition (rich in type I collagen fibers) enables both mechanical resilience and functional adaptability, crucial for the upper limb's complex movements. Recent advancements in high-resolution ultrasonography, complemented by anatomical/histological studies, have provided unprecedented insights into the fascia's microarchitecture and clinical significance. This paper delivers a simple and systematic guide as regards the sono-anatomy of deep fasciae in the upper limbs, including brachial, antebrachial and palmar fasciae as well as their continuity with adjacent structures. Integrating anatomical, histological and sonographic evidence, this article sheds light on the clinical relevance of fascia-centric approaches applied in rehabilitative and surgical treatments.