The Piriformis is muscle deep in your gluteus muscles that helps the hip joint and foot to rotate outwardly (external rotation). A spasm of this muscle can put pressure on the Sciatic Nerve and cause “Sciatica”. It is a “syndrome” because the muscle spasm also effects the joint movement and surrounding soft tissues.
Localized pain in the deep gluteal muscles when the doctor of therapist puts pressure over the area with their fingers or an instrument. Severe cases cause pain that travels partially or fully along the Sciatic Nerve pathway from the gluteal muscles to the foot.