Muscle knots in the Piriformis are located deep in the buttock, beneath the gluteal muscles, where the muscle runs from the sacrum to the greater trochanter of the femur. These trigger points often refer pain to the outer buttock, tailbone, and down the back of the thigh, sometimes mimicking sciatica with numbness or tingling in the leg and foot. People often feel a nagging ache or sharp pain that worsens with sitting, climbing stairs, or hip rotation movements.