The deep fascia has recently been a current topic in many medical fields, including rehabilitation. Some research has already focused on assessing deep fascia, however results of individual authors differ in certain aspects. This study focuses on the inter-rater reliability of ultrasound (US) measurement of the thickness of deep fascia and loose connective tissue (LCT). The aim was to define the causes of any discrepancies in measurement that could contribute to the unification of management of evaluating fascia.An observational study was performed including 20 healthy individuals in whom fascia lata of the anterior thigh was examined by US imaging and then measured in Image J software. Three raters participated in this study: the first with 6 years of US imaging experience, other two were newly trained. The measurement of fascial parameters was conducted in two phases with special consultation between them resulting in an agreement of the research team on the more precise way of measurement.Results revealed the value of inter-rater reliability ICC3,1 = 0.454 for deep fascia thickness and ICC3,1 = 0.265 for LCT thickness in the first phase and any significant difference in the second phase. This poor inter-rater reliability led to a search for possible causes of discrepancies, which authors subsequently highlighted.The findings of the study show the main pitfalls of deep fascia measurement that should contribute to the unification of evaluation.