7 Causes of Sacroiliac (SI) Joint Pain

3. New repetitive activity (or inactivity)

New repetitive activities that involve the legs, like walking long distances, can cause SI joint pain if you aren’t conditioned for these activities. For instance, if you’re vacationing and doing a lot more walking than you normally do, you might feel the pain in your SI joints.

New, repetitive inactivity can also trigger this type of pain. “Maybe you flew to Australia, so you were stuck in the same position for 14 hours or something. It’s usually that kind of thing,” Bach says. 

In these cases, it’s best to avoid whatever activity triggered it. If you walked too much, give yourself a day of rest. If you sat for too long, get moving. An ice pack on your backside right where you feel the pain may help, too, Macdonald says.

4. Hypermobility

As the name indicates, a hypermobile SI joint moves more than it should. Specifically, it’s got a little too much wiggle room. The ligaments – tissue that connects one bone to another – that connect the sacrum to the ilia (uppermost part of your hip bone) should be tight and range of motion in this joint relatively narrow.

But in a hypermobile SI joint, the ligaments are too loose. When the joint wiggles around, it can lead to inflammation and pain.

If this is the cause of your pain, you might manage it with over-the-counter painkillers, physical therapy to strengthen the muscles that hold the joint in place, and supportive devices.

“There are special SI joint belts that people wear under their clothes to help hold it in place,” Macdonald says. “It takes a lot of the pressure off, gives you stability and makes you feel a lot better.”

5. Hypomobility

On the other side of the coin, an SI joint that doesn’t move enough can be painful, too.

“When you have a lot of wear and tear, and maybe some arthritis in those joints, you’re probably going to be a little stiffer and a little less mobile,” Bach says.

Aging can also make a difference in how much your SI joints move. “The younger you are, the more mobile that joint is,” Macdonald says, “and when we age, that joint becomes more restricted.”

As with other symptoms of wear and tear, for SI joint stiffness, your health care provider may offer a combination of pain relievers, exercise recommendations and physical therapy.

6. Ankylosing spondylitis

This type of arthritis is a chronic, inflammatory condition that affects the axial skeleton, Bach says. “That’s all the midline structures, including your spine, your SI joints, and it can affect your hips, too.”

In advanced cases of this condition, joints, including the SI joints, may fuse, which inhibits motion and causes a great deal of pain. Similar to the treatment for osteoarthritis, treating ankylosing spondylitis typically includes a combination of medications to relieve pain, and exercise and physical therapy to reduce joint stiffness. Severe cases would require surgery.

7. Reactive arthritis

It’s rare, but sometimes an infection somewhere else in the body, such as in the GI tract or the genitourinary system, can lead to inflammation in the joints, including the SI joints. If you’ve recently had a stomach bug, a UTI or an STI, that could be the cause of your SI joint pain. But it usually comes with eye inflammation and pain in the urethra as well.

If your doctor diagnoses this as the cause, you may need antibiotics to treat the infection plus medications for your pain.

How is SI pain diagnosed? 

It can be hard for doctors to know for sure that your pain is in your SI joints, since it can be similar to other types of back or lumbar pain. Your doctor might perform a physical exam to rule out other possible causes and take your complete medical history. And they may do a complete blood test to look for infection or other conditions that could be causing inflammation.

Your doctor might also take images of your SI joints using:

• Pelvis X-rays
• Computed tomography (CT) scan
• Magnetic resonance imaging (MRI)

Sometimes doctors inject medication into the joint to relieve the pain. If it works, they know that the SI joints are indeed involved. After that, they’ll investigate further to uncover the exact cause of the pain.

How do you treat SI pain? ​

If your pain is mild to moderate, you can try ice and nonsteroidal anti-inflammatories (NSAIDs), like ibuprofen or naproxen. If the pain is from a bout of over- or underactivity, try doing the opposite for a few days.

“If your pain isn’t going away after a week, and it’s keeping you from doing things, then go see a doctor,” Bach says.

They may suggest you work with a physical therapist, who can help teach you how to stretch and exercise the muscles around your SI joints.

Your doctor also might recommend other medications, including:

• Muscle relaxers. These prescription meds may help pain caused by muscle spasms connected to the SI joints.
• Corticosteroids. Steroids can be injected directly into your joint to help with pain and inflammation. But this is usually a short-term solution because repeated injections can damage your cartilage. 
• Radiofrequency ablation (RFA). If your pain is bad enough, your provider can permanently block the nerves to your SI joints, though this is not used very often.

You might need to work with a rheumatologist who treats inflammatory diseases if none of these help.