A tight piriformis muscle can lead to referred pain down the leg and symptoms of sciatica because of its proximity to the sciatic nerve.The piriformis muscle is a small, flat muscle in the buttocks that connects the lower spine to the top of the femur and aids in hip rotation. When it becomes tight or spasms, it can compress or irritate the sciatic nerve, which runs directly underneath (or sometimes even through) the piriformis in some individuals.This compression can cause "piriformis syndrome,