What is sacroiliitis?

Sacroiliitis is inflammation of one or both of your sacroiliac joints. 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. They support the weight of your upper body.

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

What are the symptoms of sacroiliitis?

If you have sacroiliitis, your symptoms may include lower back pain. The pain varies for different people, at different times or in different positions.

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, groin or just below the belt line 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
• your pain is worse when you put all your weight on one leg

CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.

What causes sacroiliitis?

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 or stress on your joint caused by injuries, accidents, repetitive movements or movements involving one side of your body
• surgery — prior surgeries in the region can weaken the joint
• infection
• inflammatory conditions — for example, ankylosing spondylitis, rheumatoid arthritis, ulcerative colitis or Crohn's disease
• pregnancy — the weight of pregnancy and pregnancy hormones can make the joints more flexible and stress the SI joint

When should I see my doctor?

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
• unexplained weight loss

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

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

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

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How is sacroiliitis diagnosed?

Your doctor or physiotherapist can diagnose you with sacroiliitis by:

• asking about your symptoms and medical history — including any past accidents or injuries, your exercise habits, diet and sleep patterns
• doing a physical examination — checking how you walk and move
• referring you for tests — such as blood tests, magnetic resonance imaging (MRI), computed tomography (CT) scans, positron emission tomography (PET) scans or other imaging tests
• 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, this suggests the joint is the source of your pain

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

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

How is sacroiliitis treated?

Treatment options available for sacroiliitis include:

• physiotherapy, including stretching exercises and exercises to improve your stability
• stabilising belts and braces to support your joints and reduce movement that can cause pain
• radiofrequency denervation — a needle is placed in your joint and radio waves destroy the nerve endings to stop you feeling pain
• joint fusion surgery — joins the bones in the joint together, as a last resort when other treatments have not worked
• medicines — pain relief, steroid injections, numbing creams, non-steroidal anti-inflammatory drugs (NSAIDs) and medicines that treat the underlying cause

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

While there is little direct evidence that pain medicines treat sacroiliitis, they can help manage the symptoms of acute and chronic lower back pain. Most people with sacroiliitis recover within 2 to 4 weeks. Symptoms may return if you do not change your lifestyle.

ASK YOUR DOCTOR — Preparing for an appointment? Use the Question Builder for general tips on what to ask your GP or specialist.

What are the complications of sacroiliitis?

If sacroiliitis is not treated, you may develop chronic pain. Severe pain can limit how you move. This can affect your mental health and quality of life.

Can sacroiliitis be prevented?

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

• being physically active and stretching
• eating a healthy diet
• losing weight if you need to
• limiting your alcohol intake
• quitting smoking
• using stability belts or braces

Resources and support

For more information on sacroiliitis and its management:

• See the Musculoskeletal Health Australia website for general information about back pain and tips to manage and prevent back pain.
• Call the B.A.M. (Back pain Arthritis Musculoskeletal conditions) helpline on 1800 263 265.
• Visit the Australian Rheumatology Association to find a specialist.
• Use the Australian Physiotherapy Association search tool to find a physiotherapist.
• NPS MedicineWise has a resource for patients on lower back pain.
• MyBackPain has tips on managing back pain.
• The Australian Commission on Safety and Quality in Health Care has fact sheets on lower back pain and how to manage it.

Learn about why it is important to be physically active at the Australian Physiotherapy Association website.

For help to quit smoking, call Quitline or Aboriginal Quitline (staffed by Aboriginal counsellors) on 13 7848 (13 QUIT).

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.

Languages other than English

These resources are available in languages other than English:

• The NSW Multicultural Health Communication Service has videos on understanding pain.
• The NSW Government has a fact sheet on managing low back pain.
• You will find more translated information on back pain at Health Translations.

Information for Aboriginal and/or Torres Strait Islander peoples

The Pain Management Network has resources on chronic pain and management.