lesser sciatic foramen lesser sciatic foramen the lesser sciatic foramen is an opening (foramen) between the pelvis and the back of the thigh. the foramen is formed by the sacrotuberous ligament which runs between the sacrum and the ischial tuberosity and the sacrospinous ligament which runs between the sacrum and the ischial spine. lesser sciatic foramenimage of the pelvis showing the lesser sciatic foramendetailsidentifierslatinforamen ischiadicum minusta98a03.6.03.009ta21345fma17035anatomical terminology structure the lesser sciatic foramen has the following boundaries: anterior: the tuberosity of the ischium superior: the spine of the ischium and sacrospinous ligament posterior: the sacrotuberous ligament alternatively, the foramen can be defined by the boundaries of the lesser sciatic notch and the two ligaments. function pudendal nerve and its course through the lesser sciatic foramen the following pass through the foramen: the tendon of the obturator internus internal pudendal vessels pudendal nerve nerve to the obturator internus