Deep Buttock Muscle
Anatomically, the piriformis muscle lies deep to the gluteal muscles.
It originates from the sacral spine and attaches to the greater trochanter of the femur, which is the big, bony "bump" on the outside top of the thigh. The sciatic nerve usually passes underneath the piriformis muscle, but in approximately 15% of the population, it travels through the muscle. It is thought that acute or chronic.