Sacroiliitis is inflammation of your sacroiliac joint. This is one of the largest joints in your body. It connects your ilium (a part of your hip bone) to your sacrum (a triangle shaped bone found at the bottom of your spine). You have 2 of these joints, one on each side of your body.

Sacroiliitis is a common cause of lower back pain. It can affect your quality of life. With proper treatment you can recover.

Key facts

• Sacroiliitis is inflammation of one or both of your sacroiliac joints, which connects part of your hip to the bottom of your spine.
• Lower back pain is the main symptom of sacroiliitis; it can be a sharp and stabbing pain, or dull and achy, felt at your lower back all the way down your leg and gets worse when you sit or stand for a while.
• There are many causes of sacroiliitis, including trauma, pregnancy, getting older, inflammatory diseases, infection or arthritis.
• Your doctor can diagnose you with sacroiliitis by doing a physical examination, asking you about your symptoms and medical history, ordering tests, asking you to move in different ways, and by injecting numbing solution into your joint to see if it makes your pain disappear.
• Treatments for sacroiliitis include medicines to help manage pain, physiotherapy, radiofrequency denervation or surgery.

There are many possible causes of sacroiliitis, including:

• osteoarthritis and ageing can cause wear and tear and degeneration of the SI (sacroiliac) joint
• trauma — sudden movements and stress on your joint caused by injuries and accidents, or repetitive movements or movements involving one side of your body
• infection
• inflammatory conditions — for example, ankylosing spondylitis, rheumatoid arthritis, ulcerative colitis, Crohn's disease, Behcet's disease
• pregnancy — the weight of pregnancy and pregnancy hormones can make the joints more flexible and stress the SI joint

If you have sacroiliitis, you may feel lower back pain. The pain varies for different people.

You may feel:

• a sharp and stabbing pain, or dull and achy pain
• pain on one or both sides of your body
• pain starting at your lower back, bottom or groin that can spread all the way down your leg
• your pain gets worse when you sit or walk for a while, climb stairs or lie on the side that hurts

You should see your doctor if you have:

• back pain from an accident, such as a car accident or falling off a ladder
• back pain that does not improve after a few days
• back pain that is getting worse
• pain that continues for more than 4 weeks
• severe pain that wakes you up
• back and abdominal pain

You should see your doctor as soon as possible if you:

• have had cancer
• are prone to infection
• use intravenous drugs

For most people, back pain will resolve in a few weeks.

Your doctor or physiotherapist can diagnose you with sacroiliitis by:

• asking you questions about your symptoms, medical history, accidents or injuries you may have had
• doing a physical examination
• referring you for some tests — blood tests, MRI, CT scans, PET scans
• doing provocation tests — a series of tests where your doctor will move you in different ways to see if it causes your pain
• injecting a local anaesthetic into your sacroiliac joint — if your pain goes away, you have sacroiliitis

Your doctor will choose which tests you should do, based on your situation.

Sacroiliitis can be hard to diagnose because its symptoms are very similar to other conditions that also cause lower back pain. Your doctor will rule out other conditions that also cause lower back pain.

There are many treatment options available for sacroiliitis, including:

• medicines — pain relievers, steroid injections, numbing creams, non-steroidal anti-inflammatory drugs (NSAIDs)
• physiotherapy, including stretching exercises
• radiofrequency denervation — a needle is put in your joint and radio waves destroy your nerve endings, stopping you from feeling pain
• joint fusion surgery — surgery that joins the bones in the joint together. This is a last resort when other treatments have not worked.

You may be treated by a team of healthcare professionals, including a rheumatologist (a doctor who specialises in inflammatory conditions), physiotherapist and dietitian. Your team will create a treatment plan that considers the cause of your sacroiliitis and the type of pain you have.

Most people with sacroiliitis will recover, usually within 2 to 4 weeks; however, recurrence of symptoms may occur in people who do not change their lifestyle.

If your sacroiliitis is not treated, you may develop chronic pain. If your pain is severe, your ability to move could be limited. This can affect your mental health and quality of life.

You can make some lifestyle changes to help prevent recurrences of sacroiliitis, such as:

• being physically active
• eating a healthy diet
• losing weight if you need to
• limiting your alcohol intake
• quitting smoking