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SI joint pain, short for sacroiliac joint pain, comes from one or both of the joints where your lower spine meets your pelvis.[1][2] It’s usually felt in the lower back and buttocks, and because it can feel a lot like other kinds of low back pain, it can be hard to pin down.[1][2]
In brief
- SI joint pain is usually felt in the lower back and buttocks, usually on one side, and can spread to the hips or thighs. Long spells of sitting or standing, stairs and turning your hips can make it worse.[1][2][3]
- Physical therapy is the most common treatment. Injections, radiofrequency ablation and, rarely, fusion surgery are options when pain doesn’t settle.[2][4]
- Get help right away for numbness or weakness in both legs, numbness around your genitals or anus, or changes in bladder or bowel control.[5]
What and where are the SI joints?
You have two sacroiliac joints, one on each side of the base of your spine. Each one joins the sacrum, the triangle-shaped bone at the bottom of your spine, to the ilium, the top part of your pelvis.[2] The sacrum is made of 5 vertebrae fused together and sits between the two iliac bones.[3]
The SI joints are some of the biggest joints in your body, and you use them every time you move or shift your hips.[2] They support the weight of your upper body when you stand.[1] Their main job is to connect the spine and pelvis, so they move very little.[3]
SI joint pain, sacroiliitis and SI joint dysfunction
You’ll see these terms used side by side. Sacroiliitis is inflammation of one or both SI joints, which a doctor diagnoses. You can have pain in or near an SI joint without having sacroiliitis.[2] SI joint dysfunction is another name used for problems with the joint that cause pain.[3]
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SI joint pain symptoms
Pain in the lower back is the most common symptom, and it’s usually on one side only.[2][3] It can feel sharp and stabbing or like a constant dull ache, and it can spread from your lower back into your buttocks, hips or thighs.[2] Less often it reaches the groin, the legs or even the feet.[1]
The pain tends to get worse with:
- sitting, standing or walking for a long time[1][2]
- turning or rotating your hips[2]
- running and climbing stairs[1]
- bending over, or standing up after you’ve been sitting for a long time[3]
- sleeping on the side that hurts[1]
Lying down may ease it.[3] People with sacroiliitis are often stiff first thing in the morning, and that stiffness usually lasts for more than an hour each time they wake up.[2] The condition can make it hard to bend, lift, stay in one position or get up from a chair, and pain that lasts can disturb sleep and lead to depression.[1] For movement triggers, see our guide to SI joint pain exercises to avoid. For nights, see how to sleep with sacroiliac joint pain.
SI joint pain or sciatica?
Both can cause pain in the buttock and leg. One review describes SI joint pain as usually felt below the belt line, sometimes spreading into the groin or leg and only occasionally below the knee. It’s typically an ache, without burning, numbness or tingling.[6] Because the symptoms overlap with disc, spinal joint and hip problems, doctors rule those out before settling on the SI joint.[7] Our explainer on axial and radicular pain covers the difference between pain that stays in the back and pain that travels along a nerve.
What causes SI joint pain?
Mayo Clinic, Cleveland Clinic and MedlinePlus list these causes:
- Arthritis. Arthritis is the main cause of sacroiliitis.[2] This includes wear-and-tear osteoarthritis and ankylosing spondylitis, a type of arthritis that affects the spine.[1] Sacroiliitis is often an early symptom of ankylosing spondylitis. Psoriatic arthritis can cause it too.[2]
- Other inflammatory conditions. Crohn’s disease, ulcerative colitis and reactive arthritis can all cause sacroiliitis.[2]
- Injury. A sudden hit, such as from a car accident or a fall, can damage the joints.[1] So can landing hard on your buttocks or a past pelvic fracture.[3]
- Pregnancy. The joints loosen and stretch for childbirth (more on this below).[1]
- Not moving enough. A lack of exercise can leave the muscles around the joint tight and tense.[1]
- Cartilage wear and leg length. The cartilage between the bones can wear away, and a difference in leg lengths can also lead to pain around the joint.[3]
- Spinal fusion surgery. Surgery to fuse the spine can damage the joint and the ligaments and nerves around it.[1]
- Infection. This is rare. The risk is higher in people who have diabetes or who inject drugs.[1]
SI joint pain can follow an injury, but it more often builds up over a long period.[3] Inflammatory forms of arthritis and inflammatory bowel disease may raise the risk of sacroiliitis.[1] A 2025 review also lists scoliosis, heavy physical exertion and lumbar fusion surgery that fixes the sacrum in place as possible risk factors for SI joint pain.[4]
SI joint pain in pregnancy
During pregnancy the SI joints loosen and stretch for childbirth, and the added weight and change in the way you walk can stress them.[1] Pregnancy-related pelvic girdle pain (PGP) comes from the joints at the back or front of the pelvis stiffening or moving unevenly, and it affects up to 1 in 5 pregnant women to some degree. It can be felt across one or both sides of the lower back, and it isn’t harmful to your baby. It can be worse when you walk, use stairs, stand on one leg, turn over in bed or move your legs apart, such as when you get out of a car.[8]
The NHS suggests staying active while avoiding what makes the pain worse, resting when you can, putting equal weight on each leg when you stand, sitting down to get dressed and sleeping with a pillow between your legs. It also suggests avoiding long spells of sitting or standing, going up and down stairs too often and lifting heavy things.[8] A physical therapist may give you exercises for your pelvic floor, stomach, back and hip muscles, and sometimes a pelvic support belt or crutches. PGP tends not to clear completely until the baby is born.[8] Get exercises from a physical therapist rather than pushing your own stretches: aggressive stretching or joint mobilization can make pregnancy-related symptoms worse.[9]
How SI joint pain is diagnosed
No single test proves that pain comes from the SI joint, so it can end up as a diagnosis of exclusion, made once other causes are ruled out.[9]
History and physical exam
Your doctor will examine your back, hips and legs. Tell them when the pain started, which activities make it worse and what other health conditions you have. They may ask you to do some movements to check your range of motion and press on or around the SI joints, so say if any position, movement or pressure brings on your pain.[2]
Provocation tests
Your doctor may move your legs and hips around in different positions.[3] These provocation tests stress the SI joint, and they include the FABER (flexion, abduction and external rotation), compression and Gaenslen’s tests. When at least three of five such tests reproduce the pain, the SI joint is strongly suspected. The tests alone can give false-positive results, so the diagnosis is usually confirmed with an image-guided injection test.[7]
Imaging and blood tests
X-rays of the pelvis, a CT scan or an MRI can show the joints, and blood tests can help rule out an infection or other causes of inflammation.[2] Imaging has limits. The joint is hard to see clearly on X-rays, and scans may show changes that aren’t specific to SI joint pain. MRI is the most sensitive test for spotting sacroiliitis, the inflamed form.[6] One review says CT and MRI can’t diagnose SI joint pain that isn’t caused by inflammation, but they’re still needed to rule out inflammatory disease.[7]
Diagnostic injection
Your provider may suggest an injection into the SI joint to locate your pain accurately.[3] A local anesthetic is injected into the joint under imaging guidance. If it relieves your usual pain, that points to the SI joint as the source.[7][9] Reviews describe this as the most accurate test available, but it isn’t perfect.[6][7] One reports false-positive rates of more than 20% when anesthetic and steroid are injected together.[7]
SI joint pain treatment
No set treatment protocol has been shown to work reliably for SI joint pain, so plans are built around the person.[9] Care usually starts with physical therapy, lifestyle changes and anti-inflammatory medicines. Injections and radiofrequency treatment are options for pain that persists, and surgery is kept for severe pain that hasn’t responded to anything else.[4]
SI joint treatments at a glance
| Treatment | What the sources say |
|---|---|
| Self-care | Usual first step: ease off what provokes the pain, use ice or heat, and avoid long bed rest.[3][5][9] |
| Physical therapy | Part of first-line care. Reviews disagree on how well it works.[4][7][10] |
| Medicines | NSAIDs and muscle relaxers are used. Evidence specific to SI joint pain is thin.[2][4][6] |
| SI belt | May reduce stress on the joint and pain. Research hasn’t shown who benefits most.[4][9] |
| Steroid injection | Can relieve pain and help confirm the diagnosis. The benefit may not last.[2][6][7] |
| Radiofrequency ablation | Less common. Aims to stop nerves in the joint sending pain signals when pain persists after other care.[2][4] |
| Fusion surgery | Rare. Considered for severe pain when other treatments haven’t helped.[2][4] |
Self-care: rest, ice and heat
Advice on rest varies with the stage of the pain. For the first few days or weeks of SI joint pain, MedlinePlus suggests keeping activity to a minimum and stopping any movement that makes the pain worse.[3] For back pain in general, bed rest isn’t recommended, and the NHS advises staying active and not staying in bed for long periods.[5][11] A review of nonsurgical care describes the middle ground as relative rest: cutting back on the activities that provoke the pain, such as running, single-leg or twisting activities.[9]
MedlinePlus suggests icing your lower back or upper buttocks for about 20 minutes 2 to 3 times a day, never directly on the skin, and using a heating pad on a low setting to loosen tight muscles.[3] Walking, swimming, yoga and pilates may help ease back pain, according to the NHS, but stop any exercise or stretch that makes your pain worse and see a doctor for advice.[5]
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Medicines
Over-the-counter anti-inflammatory painkillers (NSAIDs) are a common first choice.[2][4] Cleveland Clinic advises not taking them for more than 10 days in a row without talking to your doctor. Prescription muscle relaxers are another option.[2] Talk to your doctor before using pain relievers if you have heart disease, high blood pressure or kidney disease, or have had stomach ulcers or internal bleeding, and don’t take more than the label or your doctor recommends.[3] If you’re pregnant, ask your doctor or midwife before taking an NSAID, because they have been linked to pregnancy complications.[12] A 2020 review found no studies of medicines for SI joint pain on its own, so their use rests on evidence from chronic low back pain.[6]
Physical therapy
Physical therapy is the most common treatment for sacroiliitis. A physical therapist gives you stretches and exercises to strengthen the muscles around your SI joints, which takes pressure off the joints, helps keep them stable and improves your range of motion.[2] Programs often include stabilizing exercises for the core, gluteal (buttock) and pelvic floor muscles, stretches for the lower back, hamstrings and hip flexors, and sometimes joint manipulation.[4] A home exercise program is recommended to keep the gains and, the authors hope, to help stop the pain coming back.[9] Our guide to SI joint exercises and stretches describes 7 gentle moves and the source behind each one.
The evidence is mixed. A 2017 systematic review found that manipulation, exercise and kinesio tape reduced pain and disability, though the studies were of low to average quality.[10] Another review says there’s no clear evidence yet that physical therapy works for SI joint pain that isn’t caused by inflammation, partly because studies use such different approaches, and that programs end up tailored to each person.[7] For general strengthening, see our guide to core exercises for back pain.
SI belts
An SI belt or lumbar brace can give the joint support during activity.[3] Belts compress the joint and are often worn for walking and standing. They need to sit in the right place on the pelvis, and research hasn’t yet shown who is most likely to benefit.[9] A 2025 review says belts or braces might reduce stress on the joint and pain.[4]
Injections
If the pain is long-lasting, your doctor may suggest a corticosteroid injection into the joint to ease pain and inflammation, and it can be repeated if needed.[2][3] These injections are usually given under X-ray guidance with a local anesthetic, so they can help confirm the diagnosis as well as treat it.[4][9] Reviews note that the relief from injections, and from other nonsurgical treatments, may not last.[6][7] For what happens on the day and how well they work, see our guide to SI joint injections.
Radiofrequency ablation
Less often, a doctor may suggest radiofrequency ablation (RFA) to block nerves in the joint from sending pain signals to the brain.[2] It’s an option for persistent pain that hasn’t responded to first-line care.[4] One review notes that the benefit may fade over time.[7]
SI joint fusion surgery
It’s rare to need surgery. It may be suggested if physical therapy and treatments such as RFA haven’t improved the pain. Fusion permanently fastens the joint together with surgical screws.[2] Minimally invasive fusion is usually kept for severe pain that hasn’t responded to less invasive care, and in trials it relieved pain and improved function more than nonsurgical management.[4] Many SI joint studies are small with short follow-up, so long-term results are less certain.[4] Our SI joint fusion explainer covers the surgery and what recovery involves.
If arthritis or another inflammatory disease is behind your pain, you may be referred to a rheumatologist, a doctor who specializes in inflammatory diseases.[2]
Outlook and prevention
SI joint pain often builds up over time and comes and goes, flaring with certain daily activities, sports or exercise.[9] Most people with sacroiliitis treat the cause with medicine and manage their symptoms with physical therapy. If inflammatory arthritis is the cause, the damage to the joint may be permanent. Talk to your doctor again if your symptoms come back or get worse.[2]
There’s usually no way to prevent sacroiliitis. You can lower your chances of developing arthritis by avoiding tobacco, doing low-impact exercise and following a diet and exercise plan that’s healthy for you.[2] Keeping your body weight down is one of the lifestyle changes a 2025 review says might reduce stress on the joint and pain.[4] For lifting, MedlinePlus advises bending at the knees, keeping the load close to your body and not twisting while you lift or carry.[11] Our guide to proper lifting has more.
When to get medical help
Call 911 or go to the ER if you have back pain and:[5]
- pain, tingling, weakness or numbness in both legs
- loss of feeling around your genitals or anus
- changes in your bladder or bowels, such as trouble urinating or losing control of your bladder or bowels
- changes in how your penis or vagina feels during sex, or trouble getting an erection or reaching orgasm
- chest pain
- pain that started after a serious accident, such as a car crash
Don’t drive yourself to the ER. Ask someone to drive you, or call 911.[5]
Call your doctor right away or go to urgent care the same day if you have back pain and:[3][5][11]
- you feel hot, cold, shivery or generally unwell, or you have a fever
- the pain is severe and started suddenly, or it’s getting worse quickly
- weakness or numbness in a leg, buttock, thigh or your pelvis
- pain that travels down your leg below the knee
- pain that wakes you up at night
- sudden numbness or tingling in your lower back and hips
- trouble walking or keeping your balance
- redness or swelling on your back or spine
- burning when you urinate, or blood in your urine
- severe pain that doesn’t let you get comfortable, or pain that’s worse when you lie down
- a history of cancer
See your doctor if:[2][3][5][11]
- pain near your SI joint hasn’t gotten better on its own within a week, or it’s stopping you doing day-to-day things
- it doesn’t improve after resting
- you’ve lost weight without trying, or there’s a lump or swelling in your back
- pain suddenly gets worse in other joints, with pain in your eyes and when you urinate
- you use steroids or inject drugs
Common questions
How common is SI joint pain?
Reviews put the SI joint’s share of low back pain at about 15% to 30%, and at about 20% among people whose low back pain is chronic.[4][9] Some studies estimate that around a quarter of people with low back pain have sacroiliitis. Estimates vary because low back pain has so many causes.[2]
What kind of doctor treats SI joint pain?
Care can involve pain management specialists, rheumatologists, orthopedic surgeons and physical medicine and rehabilitation physicians.[4] A physical therapist is usually part of the team too.[2]
Can massage or a chiropractor help?
MedlinePlus lists massaging the muscles of the lower back, buttocks and thighs among the steps for symptom relief.[3] Evidence for manipulation is mixed: one review points out that methods vary widely and that one well-run study found no improvement in SI joint pain after manipulation.[7]
When can I go back to sports?
One review suggests going back to the sports and exercise that bring on your pain once you’re pain-free without medicine, and building up with care, because careful monitoring during your return can help prevent reinjury.[9]
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How we checked this article
Medical review: pending. A clinician hasn’t reviewed this article yet. We last checked it against the sources below on November 6, 2026.
Sources
- Mayo Clinic. Sacroiliitis: Symptoms and causes. August 11, 2026.
- Cleveland Clinic. Sacroiliitis. Last updated August 23, 2023.
- MedlinePlus. Sacroiliac joint pain – aftercare. Review date November 7, 2024.
- Migliorini F, Lucenti L, Bardazzi T, Bell A, Cocconi F, Maffulli N. Management of sacroiliac joint pain: current concepts. Eur J Orthop Surg Traumatol. 2025;35(1):208.
- NHS. Back pain. Page last reviewed March 5, 2026.
- Falowski S, Sayed D, Pope J, et al. A review and algorithm in the diagnosis and treatment of sacroiliac joint pain. J Pain Res. 2020;13:3337-3348.
- Le Huec JC, Bourret S, Thompson W, Daulouede C, Cloché T. A painful unknown: sacroiliac joint diagnosis and treatment. EFORT Open Rev. 2020;5(10):691-698.
- NHS. Pelvic pain in pregnancy. Page last reviewed December 12, 2022.
- Prather H, Bonnette M, Hunt D. Nonoperative treatment options for patients with sacroiliac joint pain. Int J Spine Surg. 2020;14(Suppl 1):S35-S40.
- Al-Subahi M, Alayat M, Alshehri MA, et al. The effectiveness of physiotherapy interventions for sacroiliac joint dysfunction: a systematic review. J Phys Ther Sci. 2017;29(9):1689-1694.
- MedlinePlus. Low back pain – acute. Review date June 27, 2026.
- Kanakaris NK, Roberts CS, Giannoudis PV. Pregnancy-related pelvic girdle pain: an update. BMC Med. 2011;9:15.
