The short answer
Sacroiliac (SI) joint pain is usually felt on one side, below the belt line, over the bony dimple at the back of the pelvis, and often into the buttock. It tends to flare with stairs, standing on one leg and rolling in bed. A cluster of examination tests separates it from a disc or the hip, and treatment combines hands-on work to calm the joint with strength training for the hips and trunk that keeps it settled.
- SI joint pain is usually one-sided, below the belt line over the dimple at the back of the pelvis, and often into the buttock.
- Stairs, standing on one leg, rolling in bed and getting out of a car tend to aggravate it.
- No single test confirms it; a cluster of tests, done after the spine and hip are examined, is what points to the joint.
- The pelvis is not ‘out’. Manipulation reduces pain and guarding, and strength work for the hips and trunk keeps the joint settled.
- Long morning stiffness, fever, groin numbness or bladder changes need a physician first.
Many people who say they have low back pain point to the same place: one side, just below the belt, where the back of the pelvis has a small bony bump and a dimple in the skin. That spot sits over the sacroiliac joint, where the base of the spine meets the pelvis. The joint can be a real source of pain, and it is also one of the most over-diagnosed areas in the body, because the lumbar spine and the hip refer pain to exactly the same place. This article explains what the joint does, how the pain behaves, how an examination tells it apart from a disc or the hip, and what helps.
What the sacroiliac joint is
You have two sacroiliac joints, one on each side, where the sacrum (the triangular bone at the base of the spine) meets the ilium (the large wing of the pelvis). They are built for stability, not movement. Thick ligaments wrap them, the joint surfaces are ridged so they lock together, and the amount they move is measured in a few degrees.
Their job is to pass the weight of the upper body into the legs, and to absorb the twist of the pelvis every time you walk, run or climb a step. When the load on them changes faster than the surrounding muscles and ligaments can adapt, they can become irritable and painful, much like any other joint.
Where SI joint pain is felt
The typical pattern is:
- One side rather than both
- Below the belt line, over or just beside the bony dimple at the back of the pelvis
- Often into the buttock, sometimes into the back of the thigh or the groin
- Rarely below the knee
A useful informal test is to ask the person to point with one finger to where it hurts. When the finger lands on or just beside that dimple, the SI joint moves up the list. When the pain sits higher, in the middle of the back, or runs down the leg into the foot with numbness or tingling, the lumbar spine is the more likely source. See sciatica or piriformis.
What makes it worse
SI joint pain tends to respond to activities that load one side of the pelvis more than the other:
- Climbing stairs or stepping up, especially leading with the painful leg
- Standing on one leg to put on pants or shoes
- Rolling over in bed
- Getting in and out of a car
- Long walks, running, or a long stride
- Sitting for long periods on one buttock, or with legs crossed
Bending forward, which aggravates many disc problems, often matters less. That difference is one of the clues an examination uses.
Who tends to get it
Some situations come up again and again:
- Pregnancy and the months after birth. Hormonal changes loosen the ligaments, and the load on the pelvis changes quickly.
- A fall onto the buttock or a sudden misstep off a curb.
- A change in how you walk or run: a new sport, a sudden increase in mileage, or limping after a knee, ankle or foot injury.
- After a lumbar fusion, because the joints next to a fused segment take more of the movement.
- Asymmetric sports: golf, tennis, kicking sports, and lifting with one side doing more than the other.
There is also an inflammatory cause, which is different and important. Inflammatory arthritis of the SI joints (axial spondyloarthritis) usually starts before 45, causes morning stiffness that lasts well over half an hour, often affects both sides, and improves with movement rather than rest. That pattern needs a physician and a rheumatologist, and physical therapy then works alongside their care.
How an examination tells it apart
No single test proves the SI joint is the source of pain. What works is a cluster: several provocation tests that stress the joint in different directions, done after the lumbar spine and the hip have been examined. When three or more of the SI tests reproduce your familiar pain, and the spine and hip tests do not, the SI joint becomes the most likely source.
The order matters. The lumbar spine is examined first, because a disc or nerve problem can produce buttock pain that mimics the SI joint. The hip is examined next, because a stiff or irritated hip loads the pelvis unevenly and also refers pain to the buttock and groin. See how the examination tells a disc from a muscle and hip pain.
Scans are of limited help here. X-rays and MRI are useful for inflammatory arthritis, fractures and other specific problems, but for ordinary mechanical SI pain they often look normal or show changes that are common in people with no pain at all. See what an MRI changes about back pain.
The myth of the pelvis that is ‘out’
Many people with SI pain have been told their pelvis is rotated, their SI joint is out, or one leg is longer than the other, and that it needs putting back in. It is an understandable explanation, and it is not what happens. The joint moves only a few degrees and is locked by ridged surfaces and some of the strongest ligaments in the body. Studies that measure the joint before and after manipulation find the bones barely move.
Manipulation can still help, but for a different reason: it reduces muscle guarding and pain sensitivity around the joint, which gives a window in which movement and exercise are easier. That is why it is followed by loading, every time. See what a spinal manipulation actually changes.
The difference matters for how you think about your back. A pelvis that keeps ‘going out’ sounds fragile and dependent on someone fixing it. A joint that is irritable because of how it is being loaded is something you can change.
What treatment looks like
At Osteopractic Physical Therapy & Pain Relief, treatment for SI joint pain usually has three parts in the same 60-minute visit:
- Calm it down. Manipulation of the SI joint, lumbar spine or hip where the examination supports it, and dry needling of the gluteal muscles, which are often tight and tender around an irritable joint.
- Load it properly. Strength work for the gluteal muscles, the deep trunk muscles and the hips, starting with exercises that do not provoke the pain and progressing to single-leg work, because single-leg load is where the SI joint is tested in daily life.
- Change what irritates it. How you climb stairs while it is sore, how you get out of the car, how you sleep, and how your training is building, so the joint is not flared up again between visits.
A pelvic support belt can help in the short term, particularly in pregnancy, by compressing the joint while the muscles are being strengthened. It is a bridge, not a long-term answer.
The exercises that usually matter
The exact program depends on the examination, but most plans build through similar stages:
- Early: bridges, side-lying hip work and gentle breathing and bracing, performed without provoking the pain.
- Middle: step-ups, split squats and single-leg deadlifts, with the load increasing as the joint tolerates it.
- Late: the movements your life or sport actually asks for: running, lifting, the golf swing, carrying a child on one hip.
Strength on the side that hurts is compared with the other side. A gluteal muscle that is clearly weaker on the painful side is one of the most common findings, and one of the most fixable.
How long it takes
Many people notice less pain within the first few visits, once the joint has been calmed and the aggravating habits have changed. Building the strength that keeps it settled takes longer, usually several weeks of consistent work. A pain that has been coming back for years often has a long list of compensations to unwind, and that is reflected in the plan.
Progress is measured, not guessed: the provocation tests, single-leg strength and control, and the activities that used to hurt, such as stairs or rolling in bed.
When it needs a physician first
Most SI and low back pain is mechanical and safe to treat with physical therapy. Some signs need medical assessment first:
- Fever, feeling unwell, or unexplained weight loss with back pain
- Numbness in the groin or inner thighs, or changes in bladder or bowel control
- Weakness in a leg that is getting worse
- Pain that does not change with any position and is worst at night
- A history of cancer
- Long morning stiffness that eases with movement, especially under 45
Physical therapists screen for these signs in every examination and refer on when they appear. See the symptoms that mean see someone, not wait.
Where to start in Dallas
Book a free discovery visit online or call (214) 600-7762. No physician referral is required in Texas.
Sessions are 60 minutes, one-on-one with Dr. Brent Lockett, PT, DPT, at 10670 North Central Expressway, Suite 110, in North Dallas, or at your home, office or gym. More on low back pain and sciatica.
Questions people ask
How do I know if my pain is from the SI joint?
Pain on one side below the belt line, over the dimple at the back of the pelvis, that flares with stairs, standing on one leg or rolling in bed, suggests it. An examination confirms it with a cluster of tests after ruling out the spine and the hip.
Can physical therapy help sacroiliac joint pain?
Yes. Treatment combines hands-on work to calm the joint, such as manipulation and dry needling of the gluteal muscles, with strength training for the hips and trunk and changes to the movements that keep irritating it.
Is my SI joint out of place?
Almost certainly not. The joint moves only a few degrees and is held by very strong ligaments. Pain comes from irritation, not from the bones slipping, which is why strengthening matters more than repeated adjustments.
Should I wear an SI belt?
A pelvic belt can reduce pain in the short term, especially during pregnancy. It works best as a bridge while the muscles around the joint are strengthened.
Can SI joint pain cause pain down the leg?
It can refer into the buttock, the back of the thigh and sometimes the groin, but rarely below the knee. Pain into the foot with numbness or tingling points more to a nerve in the lower back.
Do I need an MRI for SI joint pain?
Usually not for mechanical SI pain. Imaging is useful when inflammatory arthritis, a fracture or another specific problem is suspected, and your physician can order it if the examination raises that concern.
Where can I get SI joint pain treated in Dallas?
Osteopractic Physical Therapy & Pain Relief treats sacroiliac pain one-on-one with Dr. Brent Lockett, PT, DPT, at 10670 North Central Expressway, Suite 110, or at your home, office or gym. No referral is needed in Texas.
