Sacroiliac joint pain

The sacroiliac joints, often called the SI joints, connect the bottom of your spine to your pelvis. You have one on each side. They move only a small amount but help transfer weight between your upper body and legs.

Pain in this area is usually felt in the low back or upper buttock. It may come from the joint itself, the strong ligaments around it, or nearby muscles. Problems in the lower spine or hip can produce similar pain.

Symptoms alone cannot confirm that the SI joint is the source. A clinician may need to consider several possible causes, especially if the pain is persistent or severe.

Sacroiliac joint pain is often a deep, dull ache on one side, close to the small dimple above the buttock. Some people feel sharper pain during certain movements.

The discomfort may spread into the buttock, groin, outer hip, or upper thigh. Pain extending below the knee, especially with tingling or numbness, is more likely to involve a nerve or another part of the back.

The pain may become more noticeable when you:

• Stand after sitting for a long time
• Climb stairs or walk uphill
• Turn over in bed
• Stand mainly on one leg
• Take long steps, run, or lift something
• Get into or out of a car

The area may feel tender, but there is usually no visible change. Redness, warmth, or marked swelling is unusual and needs medical assessment.

Common causes include strain of the joint’s supporting ligaments and muscles. This can happen after lifting, a change in exercise, repeated twisting, an awkward step, or a fall. Pain may also develop when the pelvis and surrounding muscles are handling load unevenly.

Pregnancy can place extra stress on the pelvis as body shape, posture, and movement change. Pelvic girdle pain may continue for a time after birth. Not all pain during pregnancy comes from the SI joint, so new or troublesome symptoms should be discussed with your maternity team.

Pain from the lower spine, hip, or nearby muscles may also be felt over the SI joint area.

Less common causes include osteoarthritis, which is wear-related joint change, and inflammatory sacroiliitis, meaning inflammation within the joint. Inflammatory pain may be worse after rest, cause prolonged morning stiffness, and improve with movement. It can occur as part of conditions such as axial spondyloarthritis.

Urgent causes are uncommon. These include infection in or near the joint, a pelvic or spinal fracture, and other serious conditions affecting the back or pelvis. Fever, a major injury, or rapidly worsening neurological symptoms make these causes more important to rule out.

Seek same-day medical advice if the pain is severe or worsening and you also have fever, chills, redness, warmth, or feel generally unwell. Prompt assessment is also important if you have a weakened immune system or recently had a serious infection or procedure.

Go to an emergency department or call emergency services if you have:

• New loss of bladder or bowel control
• Numbness around your genitals, anus, or inner thighs
• New or rapidly worsening leg weakness
• Severe pain after a major fall, collision, or other injury
• An inability to stand or walk after an injury

These symptoms may indicate a spinal nerve emergency or significant injury rather than a routine SI joint problem.

Book a routine appointment if the pain lasts more than a few weeks, keeps returning, disturbs sleep, or limits work and everyday activities. Arrange an assessment sooner if you have unexplained weight loss, a history of cancer, or pain that is constant and unrelated to movement.

A clinician will ask where the pain started, what makes it better or worse, and whether you have stiffness, fever, numbness, weakness, or changes in bladder or bowel control. They may also ask about pregnancy, recent injuries, infections, inflammatory conditions, and previous back or hip problems.

The examination may include your back, pelvis, hips, nerves, walking pattern, and leg strength. Several gentle pressure or movement tests can be used to see whether stressing the SI joint reproduces your usual pain. No single examination test can prove that the joint is the source.

Most recent, uncomplicated pain does not need immediate imaging. An X-ray, MRI, or CT scan may be considered after trauma or when inflammation, infection, fracture, or another condition is suspected. Scans can show structural changes, but these do not always explain pain.

For persistent pain when the diagnosis remains uncertain, a specialist may inject local anaesthetic around the joint using imaging guidance. Short-term pain relief can help show whether the joint is contributing.

Treatment depends on the likely cause and how much the pain affects you. For a recent strain, try to keep moving within comfortable limits. Long periods of bed rest can increase stiffness and reduce strength.

Temporarily reduce movements that repeatedly trigger sharp pain, but return to usual activity gradually. Heat may ease stiffness, while a wrapped cold pack may help after a recent flare. Protect your skin and use either for short periods.

Non-prescription pain medicines may help some people. Follow the package directions and ask a pharmacist whether a medicine is suitable if you are pregnant, take other medicines, or have ongoing health conditions.

Physiotherapy may focus on hip and trunk strength, flexibility, movement habits, and a gradual return to activity. During pregnancy, a physiotherapist experienced in pelvic health may suggest movement changes or a temporary pelvic support belt.

If pain continues despite these measures, treatment may include an image-guided injection. Selected people with confirmed, persistent SI joint pain may be offered procedures that reduce pain signals from nearby nerves. Surgery to fuse the joint is reserved for uncommon, carefully assessed cases.

Pain caused by a minor strain often improves over days to several weeks, although flare-ups can occur as activity increases. Pregnancy-related pelvic pain often improves after birth but may take time to settle.

Symptoms linked to arthritis or inflammation may last longer and need ongoing treatment. If recovery is slow, reassessment can check whether the pain is coming from the SI joint, hip, spine, or another structure.

Is sacroiliac joint pain the same as sciatica?

No. Sciatica usually involves irritation of a spinal nerve and often causes pain, tingling, numbness, or weakness down the leg. SI-area pain is more often centred in the upper buttock, although the patterns can overlap.

Can sacroiliac joint pain switch sides?

It can. Changes in activity or how you carry weight may affect either side. Pain that changes location can also come from the lower back, hips, or muscles.

Should I exercise?

Gentle movement is usually reasonable if there are no urgent symptoms. Avoid repeatedly forcing a movement that causes sharp or increasing pain. A physiotherapist can help if you are unsure which activities are appropriate.

Will a scan confirm the cause?

Not always. Many scan findings occur in people without pain, and mechanical SI joint pain may not create a clear visible change. The history, examination, and response to treatment are often considered together.