The sacroiliac joints link your pelvis and lower spine. They're made up of the sacrum — the bony structure above your tailbone and below your lower vertebrae — and the top part (ilium) of your pelvis. There are sacroiliac joints in both the right and left sides of your lower back. Strong ligaments hold these joints in place. The sacroiliac joints support the weight of your upper body when you stand.
Sacroiliitis (say-kroe-il-e-I-tis) is an inflammation of one or both of your sacroiliac joints — situated where your lower spine and pelvis connect. Sacroiliitis can cause pain in your buttocks or lower back, and can extend down one or both legs. Prolonged standing or stair climbing can worsen the pain.
Sacroiliitis can be difficult to diagnose, because it can be mistaken for other causes of low back pain. It's been linked to a group of diseases that cause inflammatory arthritis of the spine. Treatment might involve physical therapy and medications.
The pain associated with sacroiliitis most commonly occurs in the buttocks and lower back. It can also affect the legs, groin and even the feet. Sacroiliitis pain can be aggravated by:
- Prolonged standing
- Bearing more weight on one leg than the other
- Stair climbing
- Taking large strides
Causes for sacroiliac joint dysfunction include:
- Traumatic injury. A sudden impact, such as a motor vehicle accident or a fall, can damage your sacroiliac joints.
- Arthritis. Wear-and-tear arthritis (osteoarthritis) can occur in sacroiliac joints, as can ankylosing spondylitis — a type of inflammatory arthritis that affects the spine.
- Pregnancy. The sacroiliac joints must loosen and stretch to accommodate childbirth. The added weight and altered gait during pregnancy can cause additional stress on these joints and can lead to abnormal wear.
- Infection. In rare cases, the sacroiliac joint can become infected.
As with other conditions that cause chronic pain, sacroiliitis can result in depression and insomnia.
During the physical exam, your doctor might try to pinpoint the cause of your pain by pressing on places on your hips and buttocks. He or she might move your legs into different positions to gently stress your sacroiliac joints.
An X-ray of your pelvis can reveal signs of damage to the sacroiliac joint. If ankylosing spondylitis is suspected, your doctor might recommend an MRI — a test that uses radio waves and a strong magnetic field to produce very detailed cross-sectional images of both bone and soft tissues.
Because low back pain can have many causes, your doctor might suggest using numbing injections (anesthetics) to help with the diagnosis. For example, if such an injection into your sacroiliac joint stops your pain, it's likely that the problem is in your sacroiliac joint. However, the numbing medicine can leak into nearby structures, and that can reduce the reliability of this test.
Corticosteroids can be injected directly into the sacroiliac joint to reduce inflammation and pain. In some cases, your doctor might inject an anesthetic into the joint to help confirm the diagnosis.
Treatment depends on your signs and symptoms, as well as the cause of your sacroiliitis.
Depending on the cause of your pain, your doctor might recommend:
- Pain relievers. If over-the-counter pain medications don't provide enough relief, your doctor may prescribe stronger versions of these drugs.
- Muscle relaxants. Medications such as cyclobenzaprine (Amrix, Fexmid) might help reduce the muscle spasms often associated with sacroiliitis.
- TNF inhibitors. Tumor necrosis factor (TNF) inhibitors — such as etanercept (Enbrel), adalimumab (Humira) and infliximab (Remicade) — often help relieve sacroiliitis that's associated with ankylosing spondylitis.
Your doctor or physical therapist can help you learn range-of-motion and stretching exercises to maintain joint flexibility, and strengthening exercises to make your muscles more stable.
Surgical and other procedures
If other methods haven't relieved your pain, you doctor might suggest:
- Joint injections. Corticosteroids can be injected into the joint to reduce inflammation and pain. You can get only a few joint injections a year because the steroids can weaken your joint's bones and tendons.
- Radiofrequency denervation. Radiofrequency energy can damage or destroy the nerve tissue causing your pain.
- Electrical stimulation. Implanting an electrical stimulator into the sacrum might help reduce pain caused by sacroiliitis.
- Joint fusion. Although surgery is rarely used to treat sacroiliitis, fusing the two bones together with metal hardware can sometimes relieve sacroiliitis pain.
Lifestyle and home remedies
Home treatments for sacroiliitis pain include:
- Over-the-counter pain relievers. Drugs such as ibuprofen (Advil, Motrin IB, others) and acetaminophen (Tylenol, others) may help relieve pain associated with sacroiliitis. Some of these drugs can cause stomach upset, or kidney or liver problems; the Food and Drug Administration recently strengthened its warning about an increased risk of heart attack and stroke with use of nonsteroidal anti-inflamatory drugs, such as ibuprofen. Read labels and take only as directed.
- Rest. Modifying or avoiding the activities that worsen your pain might help reduce the inflammation in your sacroiliac joints. Proper posture is important.
- Ice and heat. Alternating ice and heat might help relieve sacroiliac pain
Preparing for an appointment
You're likely to start by seeing your primary care provider. He or she may refer you to a rheumatologist or an orthopedic surgeon.
What you can do
When you make the appointment, ask if there's anything you need to do in advance, such as fasting before having a specific test. Make a list of:
- Your symptoms, including any that seem unrelated to the reason for your appointment
- Key personal information, including major stresses, recent life changes and family medical history, particularly if anyone in your immediate family has had similar symptoms
- All medications, vitamins or other supplements you take, including the doses
- Questions to ask your doctor
Take a family member or friend along, if possible, to help you retain the information you're given.
For sacroiliitis, some questions to ask your doctor include:
- What's likely causing my symptoms?
- What are other possible causes?
- What tests do I need?
- Is my condition likely temporary or chronic?
- What's the best course of action?
- What are the alternatives to the primary approach you're suggesting?
- How can I best manage this condition with my other health conditions?
- Are there restrictions I need to follow?
- Should I see a specialist?
- Are there brochures or other printed material I can have? What websites do you recommend?
Don't hesitate to ask other questions.
What to expect from your doctor
Your doctor is likely to ask you questions, including:
- When did your symptoms start?
- Have your symptoms been continuous or occasional?
- Where exactly is the pain and how severe is it?
- Does any type of activity worsen or lessen the pain?
Content Last Updated: April 22, 2021