Piriformis originates on the sacrum and inserts on the medial surface of the head of the femur. It is the principal lateral rotator of the hip. The sciatic nerve may pass under or through the piriformis, causing entrapment.
Much sciatic pain is caused by the piriformis, as well as restless leg syndrome.
Its trigger points typically refer into the leg, the hip, and the low back. This muscle attaches to the side of the sacrum, which is the wide, flat bone at the base of your spine just above your tailbone. Its main job is to rotate the leg outward, but it also helps to hold the hip in joint when it's bearing weight. Your sciatic nerve, which is the nerve that goes down the back of your leg, passes under or through this muscle, so tightness in the piriformis can cause sciatica, which is pain down the back of the leg. Trigger points in this muscle can cause pain in the back of the leg, the hip, and the low back.