LKnative - Popliteal sciatic nerve block 
The yellow sciatic nerve (SN) emerges from the lower border of the triangular piriformis muscle
1 – Anatomy of the sciatic nerve
The sciatic nerve emerges from the pelvis through the greater sciatic foramen underneath the piriformis muscle
It descends in the midline of the thigh between the greater trochanter and the ischial tuberosity