I won't go through the symptoms and diagnosis here. There are lots of places on the web that do this just fine.
The first bugger is getting it diagnosed. From what I know there isn't a specific test for it, so you end up coming to Piriformis Syndrome through a process of elimination. A bulging L4/L5 disc is the most common alternative diagnosis. Some people will claim "I have sciatica." Sciatica is more of a symptom than a cause. Piriformis Syndrome causes sciatica symptoms, but so do other things.
The second bugger is to stretch that baby out and get it calmed down. I've found the following the most helpful:
- Check the range of motion for internal and external rotation. Stretch appropriately to improve ROM if not good or symmetrical.
- Massage. A tennis ball works great.
- Stretching. Here are a couple.
- Piriformis is an external rotator. If it's tight and in spasm it may be because the other extneral rotators (such as gluteus maximus) aren't doing what they're supposed to, causing Piriformis to do more work. Check recruitment and strength of other external rotators.
- Driving. Do you let your legs stay splayed out against the door or center console?
- Sitting. Do you hook your ankles under the seat?