This is an illustration of the Piriformis and the sciatic nerve showing the 4 possible pathways the sciatic can take passing the Piriformis.
1-The Sciatic runs down and behind the Piriformis, this is the normal pathway.
2- The Sciatic splits around the Piriformis.
3-The Sciatic splits with one part going through the Piriformis causing constant pain from pressure especially when it is inflamed.
4- The entire Sciatic goes through the Piriformis and causing pain almost all the time especially when the Piriformis is inflamed or has direct pressure.