Something I've been seeing a lot in the clinic is people showing up saying, "Oh my sciatica is flared up and then they point to their sacroiliac joint." That's where your sacrum butts your ilium and create those little dimples that you see a little baby's lower backs. That's called your SI joint and people do have pain there, but sciatica is defined by pain that exits the lumbar spine going down the leg, passing the knee joint. Until it passes the knee joint it's not considered a sciatica, it's only considered a lumbar radiculopathy. Sciaticas are caused by one of two things. One is some type of space occupying lesion in the lumbar spine. That can be arthritis, a disc bulge, stenosis, things of that nature. Or it could be by over contracture of a muscle in your booty called the piriformis muscle, which basically chokes and clamps down the sciatic nerve and will send pain down your leg. Normally people who are having piriformis syndrome are people that are seated for long periods of time without standing, whether you're doing car travel or it's your business to be seated at a desk for long periods of time. Lumbar disc herniations will have more spasm around the lumbar spine, not just the buttock, and those will send pain down your leg as well.
I hope you learned something and I want you to all know that your bodies are amazingly strong and capable of doing anything you put your mind to. Have a great one.