The sacrotuberous ligament has a broad attachment to the sacrum, sacroiliac joint and posterior iliac bone. It narrows as it passes to the ischium, spiralling slightly. Its superficial fibres are in continuity with the biceps femoris and thus link with the hamstrings. The ligament is part of a fascial continuum extending from the foot to the head. Gluteus maximus attaches to its posterior surface as may piriformis, superior and inferior gemellus and obturator internus.A variable membranous reflection of the distal ligament [the falciform ligament] runs along the ischial ramus towards the obturator fascia with which it may fuse.
The ligament runs parallel and medial to the sciatic nerve, with which it may be confused. It is echogenic, as is the nerve and is of similar size. If confused, trace the structure back to the ischial tuberosity. The sciatic nerve passes lateral to the tuberosity and the ligament attaches to its superficial aspect.
The pudendal nerve lies immediately anterior to the ligament. Entrapment of the nerve can cause a large number of clinical complaints. Ultrasound guided injection of cortisone and local anaesthetic through the mid to distal ligament may relieve symptoms and is thus also a useful clinical test.
Irritation of the ligament at the junction with the hamstrings can cause localised pain. Swelling, reduced echogenicity and focal tenderness are noted. Ultrasound guided injection can easily be performed.
Avulsion of the ischial tuberosity epiphysis in mid to late teen sportsmen and women can have severe consequences. The role of the ligament will be examined.