Assessment of the Fascial System Thickness in Patients with and Without Low Back Pain: A Narrative Review

Background and Objectives: The hypothesis that fascial thickness variability may serve as a biomarker for low back pain (LBP) requires a clear understanding of typical thickness values in both LBP and non-LBP populations—an area still lacking in the literature. This narrative review aims to define reference values and patterns of variability for the superficial fascia, deep fascia, and subcutaneous tissue in individuals with and without LBP. Methods: A literature search was conducted in PubMed and ScienceDirect using keywords such as superficial fascia, deep fascia, thoracolumbar, subcutaneous fat, back pain, lumbar, thorax, and thickness. Inclusion criteria focused on human studies with proper identification of the relevant soft tissue structures. A total of 21 studies, published up to February 2024, met the inclusion criteria and were analyzed. Results: The review revealed notable intra- and inter-study variability in the thickness of the investigated structures. In LBP populations, both deep fascia and subcutaneous tissues were generally equal to or thicker than in controls (non-LBP), whereas consistent data on superficial fascia thickness remain limited. Age, sex, and anatomical location were discussed as potential influencing factors. Conclusions: These findings support the establishment of reference thickness values for subcutaneous and fascial tissues and encourage further investigation into their structural and functional roles in LBP. The observed variability may offer a basis for patient- and site-specific assessment and intervention strategies.