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.

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
The following pass through the foramen:
 * the tendon of the obturator internus
 * internal pudendal vessels
 * pudendal nerve
 * nerve to the obturator internus