The objective of this study was to evaluate the intrinsic preload of the sacrotuberous ligament. Preload measurements and anatomical experiments were performed on 20 specimens from 10 human cadavers and assessed to consider the thesis of the ligamentous tension band system as a possible load distribution. The result was an unexpectedly high preload force with an overall average of 118 N ± 74 N. Age has been significantly different between females and males in the cohort (median 94 vs. 77 years). Nevertheless, there is preliminary evidence of the sex-dependent sacrotuberous ligament preload force with an average value of approximately 65 N for the 10 female cadaver specimens and 172 N for the 10 male cadaver specimens. The assessment of further influencing factors and their statistical evaluation also showed a dependence of the sacrotuberous ligament preload force on body height, age and elastin content. Thus, the sacrotuberous ligament is more preloaded in the cadaver than previously assumed in the literature. Therefore, and contrary to most assumptions, it could possibly also be more preloaded in a living person in an upright position under a muscular load. This leads to the hypothesis that pelvic stability is more dependent on ligamentous preload than previously thought. These considerations should be taken more into account in numerical simulations of sacroiliac joint function.