Lower back pain has many causes. One of the most overlooked is the sacroiliac (SI) joint — a small but load-bearing joint deep in your pelvis. When it’s irritated or inflamed, the pain can feel just like sciatica, a pulled muscle, or a disc problem. Many people get treated for the wrong thing for months before the real source is found.
Research published in Pain Practice (2024) estimates that SI joint dysfunction accounts for 15 to 30 percent of all mechanical low back pain cases. That’s a wide swath of people who may be living with unnecessary pain simply because this joint isn’t on anyone’s radar.
Up to 30% of mechanical low back pain cases may originate in the SI joint — yet it remains one of the most underdiagnosed sources of pelvic and lower back pain. (Pain Practice, 2024)
What Is the Sacroiliac Joint?
Your SI joint sits where the base of your spine meets your pelvis. You have two of them — one on each side. They connect the sacrum (the triangular bone at the bottom of your spine) to the iliac bones of your pelvis. These joints don’t flex much, but they’re built to absorb shock and transfer weight between your upper and lower body.
When the SI joint becomes inflamed, stiff, or slightly out of position, pain follows. Gardening, shoveling, running, or even sitting in a car for a long stretch can push it past its limit. In spring especially, when people ramp up outdoor activity after a slower winter, SI joint flare-ups are common.
What Does SI Joint Pain Feel Like?
The pain is usually one-sided, sitting low in the back or deep in the buttock. Unlike general low back pain that spans the whole lumbar area, SI joint pain tends to be something you can point to with a single finger.
Common signs include:
- A dull, deep ache in one buttock or the lower back
- Pain that gets worse when climbing stairs, standing on one leg, or stepping out of a car
- Stiffness first thing in the morning or after sitting for a long time
- Discomfort that shifts when you change positions
The pain may travel into the upper thigh or groin, but it rarely reaches the knee, and true numbness or muscle weakness are uncommon.
Is It Sciatica or SI Joint Dysfunction?
This is one of the most common questions people ask — and with good reason. Both conditions can cause pain that travels from the low back into the buttock and leg, often on one side.
The key difference is how far and how the pain travels. Sciatica follows the sciatic nerve down the back of the leg, sometimes reaching the foot, and is often accompanied by numbness, tingling, or leg weakness. SI joint pain rarely goes below the knee, and neurological symptoms like weakness or true numbness are uncommon because the nerve isn’t being physically compressed.
A 2024 systematic review in the Journal of Manual & Manipulative Therapy analyzed 16 randomized controlled trials involving 421 adults with SI joint dysfunction. The researchers found that manual therapy produced a statistically significant, moderate improvement in disability scores compared to exercise-only approaches — suggesting that hands-on care, when the condition is correctly identified, can make a meaningful difference.
Simple Exercises You Can Do Right Now
These movements can reduce stiffness and take pressure off the SI joint. Move slowly and stop if any exercise makes your pain worse.
Figure-four stretch: Lie on your back with both knees bent. Cross one ankle over the opposite knee. Gently pull both legs toward your chest. Hold for 30 seconds, then switch sides. This targets the piriformis muscle, which sits right next to the SI joint and often tightens when the joint is irritated.
Knee-to-chest: Still on your back, pull one knee gently toward your chest and hold for 20 to 30 seconds. This releases pressure along the lower back and pelvis.
Bridge: Lying on your back with knees bent and feet flat, slowly lift your hips until your body forms a straight line from knees to shoulders. Hold 3 to 5 seconds, lower slowly. Repeat 10 times. This strengthens the glutes, which help stabilize the SI joint.
A 2025 randomized controlled trial published in the Journal of Bodywork and Movement Therapies found that adding piriformis stretching to standard treatment produced significantly better pain and functional outcomes in patients with SI joint dysfunction, compared to conventional therapy alone.
How to Prevent SI Joint Pain Going Forward
Warm up before outdoor work. Whether you’re gardening, running, or doing yard work, spend five minutes doing hip circles, gentle squats, and slow back extensions before you start. Cold muscles and cold joints tolerate sudden load poorly.
Lift with your legs, not your back. Keep objects close to your body, avoid twisting while holding weight, and plant your feet before you pick anything up. This protects the pelvis as much as the spine.
Strengthen your core and glutes. Weak stabilizers put extra stress on the SI joint with every step. Exercises like bridges, clamshells, and bird-dogs help the joint stay supported during daily movement. A network meta-analysis in Pain Physician (2023) found that combining manual therapy with targeted exercise produced the best outcomes for SI joint pain — better than either approach alone.
The Bottom Line
SI joint dysfunction is one of the most underdiagnosed causes of lower back pain. If your lower back pain sits off to one side, doesn’t follow a typical sciatica pattern, and hasn’t responded to standard treatments, the SI joint is worth a closer look.
A proper evaluation — including movement tests and a hands-on physical exam — can help identify whether the SI joint is the source. From there, treatment options include targeted exercises, physical therapy, chiropractic care, and in some cases, guided injections. Getting the right diagnosis is the first step toward getting the right relief.
Sources & Further Reading
- Szadek KM et al. “Sacroiliac joint pain.” Pain Practice, 2024. https://pubmed.ncbi.nlm.nih.gov/38155419/
- Pourahmadi M et al. “Efficacy of manual therapy for sacroiliac joint pain syndrome: a systematic review and meta-analysis.” Journal of Manual & Manipulative Therapy, 2024. https://pubmed.ncbi.nlm.nih.gov/38353102/
- Alshehri A et al. “Additional effects of piriformis stretch in the management of sacroiliac joint dysfunction: a randomized control trial.” Journal of Bodywork and Movement Therapies, 2025. https://doi.org/10.1016/j.jbmt.2025
- Hoang TS et al. “Comparative Efficacy of Clinical Interventions for Sacroiliac Joint Pain: Systematic Review and Network Meta-analysis.” Pain Physician, 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10562251/
- Liu Z et al. “Advancements in sacroiliac joint reduction for enhancing lumbosacral pain relief and achieving balanced gait.” Medicine (LWW), 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC11651511/
