I've been told I have piriformis syndrome caused by a pinched sciatic nerve. How does the sciatic nerve get pinched?

The sciatic nerve is a large nerve that starts in the low back and goes down the back of the leg from hip to foot. As it travels through the buttocks area, it passes out of the pelvis through the a hole called the greater sciatic foramen. Once it goes through this hole, it passes just below the piriformis muscle (PM).

In a small number of people (approximately 15 per cent), the sciatic nerve actually passes through the PM. Or sometimes, it is located above the PM rather than below it. In either case, contraction or tightness of the PM puts pressure on the sciatic nerve causing painful symptoms. This is just one of many possible causes of sciatica.

The pain occurs in the low back and/or buttock areas. It often travels down the leg to the knee and even down to the foot. Besides pain, patients with sciatica report numbness, weakness, and trouble moving or controlling the leg.