You may have heard your grandpa or an older coworker whimper, "Oh, my sciatica!" But sciatica, a pain that occurs along the sciatic nerve, can happen to anyone at any age, although it is more like to occur between 30 and 50 years of age. For some people, it's a minor annoyance, but for others it's chronic and debilitating - a literal "pain in the butt."

The sciatic nerve is the longest nerve in the body, and when it's squeezed or compressed, you may feel the far-reaching pain of sciatica. It can radiate from low in the back, into the buttocks, into the thigh and calf, or all the down way to the toes. Sciatica usually affects one side of the body, and the pain may shift from stinging and sharp to tingling and numb. Depending on the person, standing too long, sitting too long, sneezing, coughing, or laughing can trigger or worsen sciatica pain.

Causes of sciatica include bone irregularities from osteoarthritis that cause protrusion onto the nerves or swelling from a sprained ligament. Spinal stenosis, which is a narrowed spinal canal, may also set off sciatic pain. But the most common cause of sciatic pain is a herniated or ruptured disc. The discs cushioning the bones of the spine have tough, protective covers. Due to trauma or wear and tear, these usually resilient discs can rupture or their gel-like contents can slide out and compress nerves, causing pain.

In some people, no cause for sciatica can be found. A couple of surprising suspects may be to blame for this mysterious sciatica pain, however…

Sciatica suspect: Sacroiliac joint dysfunction (SIJD)

To understand the sacroiliac (SI) joint, you need to break the word sacroiliac into two parts: sacro and iliac. The "sacro" means your sacrum, a strong, triangle-shaped bone wedged between your hip bones at the base of your back. And the "iliac" part comes from ilium, your butterfly-wing-shaped pelvic bones. So, where these two points join, you have your sacroiliac joint, the union between your spine and your pelvis.

In SIJD, the joint may get inflamed, injured, or simply erode with age. Pregnant women sometimes experience troubles with their SI joint due to the extra weight and when hormones are released to help loosen joints and muscles in preparation for birth. And some people have extra-flexible joints naturally. SI-related injuries and strains are also common among women who practice yoga.

It's been acknowledged for a while that SIJD can trigger low back pain. In recent years, researchers have also discovered that pain neurotransmitters, chemicals that send messages through your body, could move from the injured SI joint and irritate the sciatic nerve, causing that signature sciatica ache.

You may be at risk of SI-related sciatic pain if you have poor posture, weak muscles, or ankylosing spondylitis or psoriatic arthritis. Treatments for SIJD include icing, over-the-counter pain medications, physiotherapy, and cortisone injections. To prevent flare-ups, avoid any trigger activities for awhile and focus instead on stretching and strengthening the muscles surrounding the hips. And pay attention to your posture and lifting habits.

Sciatica suspect: Piriformis syndrome

Athletes and couch potatoes alike may be able to link their sciatica-like pain to their piriformis muscle. This muscle originates inside of your pelvis girdle and stretches out to meet up with your thigh bone.

In piriformis syndrome, the tightened or injured muscle pinches or pushes the nearby sciatic nerve and triggers the painful symptoms of sciatica. Though it's rare, it's also very treatable with stretching, massage, and avoidance of the pain's likely causes, whether it is too much sitting or too many laps around the track. As with SI joint dysfunction, piriformis pain may respond to pain medications or cortisone injections.

To learn more about other causes and treatments for sciatica, see our factsheet on sciatica.

Amy Toffelmire