The piriformis is a small, flat muscle located in the buttock region, beneath the larger gluteal muscles. It plays a crucial role in the movement of the hip, helping to rotate the thigh outward and stabilize the pelvis during activities like walking and running. This muscle is also significant because it is located near the sciatic nerve, which runs from the lower back down the leg. In some cases, tightness or spasms in the piriformis can lead to a condition known as piriformis syndrome, causing pain and discomfort in the buttocks and down the leg.