The sacrotuberous ligament is a broad triangular ligament from the posterior sacrum and ilium to the ischial tuberosity. It forms the posterior boundary of the lesser sciatic foramen (with the sacrospinous ligament as the floor). The long head of biceps femoris has a fibrous connection to the sacrotuberous ligament in 50% of individuals — this anatomical link means that hamstring tightness increases sacral nutation forces.
| Origin | Posterior iliac spines, lower sacrum, and coccyx |
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| Insertion | Ischial tuberosity (medial border) — the broad insertion gives it a wide lever arm |
| Actions | Resists sacral counternutation; forms the lesser sciatic foramen roof; the biceps femoris long head may arise partly from it |
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The sacrotuberous ligament tension test (passive SLR increasing sacral counternutation) is used in osteopathic and manual therapy assessment of SIJ function. Injection of the ligament at the ischial tuberosity treats sacrotuberous ligament strain. The ligament can be palpated deep in the buttock between the ischial tuberosity and the coccyx.
Ligament overload from hamstring tightness or sacral hypermobility producing deep buttock pain managed with targeted injection and SIJ stabilisation.
