Sacroiliac Joint Dysfunction: Symptoms and Care

SI joints and load transfer

MedlinePlus explains that the sacroiliac joint is where the sacrum meets the iliac bones. The sacrum, at the base of the spine, is made of five vertebrae fused together, and the two iliac bones form the sides of the pelvis, with the sacrum sitting between them.

The main purpose of the joint is to connect the spine and the pelvis, so there is very little movement there. Mayo Clinic adds that the sacroiliac joints support the weight of the upper body when standing. Because they transfer load between the trunk and the legs, activities such as standing for a long time, climbing stairs or getting up from a chair can bring on symptoms.

Mechanical dysfunction versus inflammatory sacroiliitis

Two related terms are often mixed up. MedlinePlus uses SIJ dysfunction for pain arising around the joint from causes such as pregnancy, arthritis, uneven leg length, worn cartilage, injury or muscle tightness. Mayo Clinic describes sacroiliitis as swelling and irritation (inflammation) of one or both sacroiliac joints.

Mayo Clinic explains that sacroiliitis has been linked to diseases that cause inflammatory arthritis of the spine, such as ankylosing spondylitis and psoriatic arthritis, and to inflammatory bowel disease. These conditions are diagnosed and treated differently from mechanical pain, which is why it matters to have the cause assessed instead of assuming every SIJ pain is the same.

Pain and functional limitations

MedlinePlus lists the symptoms of SIJ dysfunction as:

pain in the lower back, usually on one side only
hip or, more commonly, buttock pain
discomfort when bending over or standing up after sitting for a long time
pain that improves when lying down

Mayo Clinic adds that sacroiliitis pain may spread down one or both thighs and sometimes to the groin or feet, and can be made worse by sitting, standing or walking for a long time, running, climbing stairs or sleeping on the painful side. It can make bending, lifting, staying in one position and rising from a chair difficult, and lasting pain can affect sleep and mood. Our guide on buttock pain covers related symptoms.

Possible causes and associated contexts

The two sources list these causes and contexts:

Pregnancy: the pelvis widens and its ligaments stretch, and added weight and a changed way of walking stress the joints.
Arthritis: wear-and-tear osteoarthritis, worn cartilage between the bones and inflammatory types such as ankylosing spondylitis.
Injury: landing hard on the buttocks, a fall or a road accident, or a history of pelvic fractures.
Muscle tightness and lack of exercise, and a difference in leg length.
Spinal fusion surgery, which can affect the joint, and, rarely, infection, more likely in people with diabetes or who inject drugs.

MedlinePlus notes that although SIJ pain can follow an injury, it more often develops over a long period.

Lumbar, hip and other differential diagnoses

Mayo Clinic points out that sacroiliac pain can be hard to diagnose because it resembles other causes of low back pain. Pain in the lower back and buttock can come from the lumbar spine, from a nerve root, from the hip joint or from muscles around the pelvis.

Leg pain with numbness or tingling, for example, may point more towards a nerve problem; our guides on a pinched nerve in the lower back and piriformis syndrome cover these. Sorting out the source is part of the clinical assessment, and several problems can coexist.

Warning signs requiring medical assessment

MedlinePlus advises contacting your health care provider if you have:

sudden numbness or tingling in the lower back and hips
weakness or numbness in the legs
problems controlling your bowel or bladder
a sudden increase in pain or discomfort
slower than expected healing
fever
a sudden increase in pain in other joints, with eye pain or pain when passing urine

Problems controlling the bladder or bowel, or numbness and weakness in the legs, need same-day urgent assessment. Pain after a significant fall or accident, or with fever, should also be checked promptly. These situations should not be handled through a routine appointment or an online form.

Clinical evaluation and limits of isolated tests

MedlinePlus explains that to help diagnose an SIJ problem, the provider may move your legs and hips in different positions. X-rays or a CT scan may be needed, and in some cases an injection into the joint is used to locate the source of pain more precisely. If pain does not improve as expected, further imaging such as CT or MRI and blood tests may be used to look for a cause.

No single movement test confirms the source of pain on its own, and self-tests at home are not a substitute for an examination. Blood tests and imaging are particularly relevant when an inflammatory cause such as sacroiliitis is suspected.

Activity adaptation and rehabilitation

For the first few days or weeks, MedlinePlus suggests reducing activities that make the pain worse, applying ice to the lower back or upper buttock for about 20 minutes two to three times a day (never directly on the skin), using a heating pad on a low setting to relax tight muscles, and massage of the lower back, buttock and thigh. A sacroiliac belt or lumbar brace can be used for support during activity in some cases.

MedlinePlus describes physical therapy as an important part of recovery, to relieve pain and increase strength, and advises asking your provider or therapist which exercises to do. Our guide on SI joint stretches covers exercises separately. Forceful self-manipulation to “unlock” the joint is not recommended. In our physiotherapy practice in Bilbao we offer individual rehabilitation for adults after assessment (consultations are in Spanish).

Where the sources differ

The two pages cover different but overlapping topics, and they differ in several ways:

Scope. MedlinePlus covers SIJ pain and dysfunction in general; Mayo Clinic covers sacroiliitis, the inflammatory form. Not every SIJ pain is sacroiliitis.
Rest. MedlinePlus says to keep activity to a minimum and that the more rest the better, at least at first. It also describes physical therapy and exercise as central. Prolonged rest is not a rule for everyone, and how activity is adapted is best decided individually.
Medicines and injections. MedlinePlus mentions nonprescription painkillers, naming products, with precautions for people with heart, kidney or stomach problems, and an injection for chronic pain. We mention only the groups. Mayo Clinic’s page mentions physical therapy and medicines without detail.
Support belts. MedlinePlus suggests a sacroiliac belt or lumbar brace for support; neither source says everyone needs one.

In summary

Sacroiliac joint dysfunction causes low back and buttock pain, usually on one side, which is worse when bending or standing up after sitting and better when lying down. Pregnancy, arthritis, injury and muscle tightness are common contexts, and sacroiliitis is a related inflammatory condition linked to inflammatory arthritis. The source of pain is confirmed through examination, sometimes with imaging or an injection.

Symptoms often improve with a period of reduced aggravating activity, ice or heat, pain relief and physical therapy. A simple record helps: list the tasks that are difficult, how long you can do them (sitting, walking, stairs) and how this changes over the weeks. Seek urgent help for leg weakness or numbness, bladder or bowel problems, fever or a sudden increase in pain.

Frequently asked questions about sacroiliac joint dysfunction

These answers are general information and do not replace an examination or individual medical advice.

Can I unlock an SI joint myself?

There is very little movement at this joint, and the official sources do not recommend self-manipulation. Rest from aggravating activities, ice or heat and exercises guided by a professional are the recommended approach.

What can cause sacroiliac joint pain?

Pregnancy, osteoarthritis and inflammatory arthritis, injuries such as a hard fall onto the buttocks, a difference in leg length, muscle tightness and, rarely, infection.

Is sacroiliitis the same as SI joint dysfunction?

No. Sacroiliitis is inflammation of the joint, often linked to inflammatory arthritis or bowel disease. SIJ dysfunction is a broader term for pain arising from the joint and the tissues around it.

Can symptoms improve?

Yes. MedlinePlus says sticking to a care plan of rest, ice and exercise helps symptoms improve. The time this takes varies; if pain is not settling as expected, your provider may arrange further tests.

Does one test or a scan confirm the source?

No single test does. Diagnosis combines the examination, sometimes X-rays, CT or MRI, blood tests if inflammation is suspected, and occasionally an injection into the joint to locate the pain.

When should pain or neurological changes be assessed urgently?

If you have weakness or numbness in the legs, numbness in the lower back and hips, problems controlling your bladder or bowel, fever, or a sudden increase in pain.

Sources

This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.