What causes piriformis syndrome.could it cause pain in the whole leg and knee?does it cause difficulty in stepping on foot.please help?

Pyriformis syndrome: Pyriformis syndrome is pain in the buttocks cause by imbalance of the pyriformis muscle that crosses near the sciatic nerve that can cause sciatica just like a herniated disc. I have had this and there are some great online stretching exercises to help as well as to diagnose this condition. See your pcp and ask to see a good physical therapist who may help you sort things out.