Piriformis Muscle Definition

The piriformis muscle is a small muscle that begins at the front surface of the sacrum (the V-shaped bone between the buttocks at the base of the spine) and passes through the greater sciatic notch to attach to the top of the thigh bone (femur). The sciatic nerve runs directly beneath this muscle, so when the piriformis muscle becomes tight, it can place pressure on the sciatic nerve and create leg pain.