If you’re pregnant and feeling deep, aching pain around your lower back, hips, or even near your buttocks, especially when walking, turning in bed, or standing on one leg, you may be experiencing sacroiliac (SI) joint pain. This is one of the most common musculoskeletal complaints during pregnancy, and as a physical therapist, I see it every week in the clinic.
Let’s break down why it happens, how it’s connected to your pelvic floor and posture, and most importantly what you can do to relieve it.
What Is the SI Joint?
The sacroiliac joints are the two small but mighty joints that connect your sacrum (the base of your spine) to your pelvic bones (the ilia). They play a critical role in transferring load between your upper body and legs, providing both stability and slight mobility.
During pregnancy, these joints become especially important as your center of gravity shifts, your ligaments loosen, and your body adapts to support your growing baby.
The Role of Hormones
Around the end of the first trimester, your body starts producing relaxin, a hormone that helps soften ligaments and prepare your pelvis for childbirth. This is essential for labor, but it also means that the joints of your pelvis, including the SI joints, can become more mobile and less stable.
When those stabilizing ligaments loosen, your muscles, especially your pelvic floor, deep core, and glutes, must step up to help stabilize the area. If those muscles are weak, tight, or not coordinating well, the SI joints can become irritated and painful.
How the Pelvic Floor Fits In
Your pelvic floor muscles are like a hammock or sling that support your bladder, uterus, and rectum. But they also play a huge role in pelvic stability.
When the pelvic floor works together with your deep abdominal muscles (transverse abdominis), multifidus (small spinal stabilizers), and glutes, the pelvis stays supported and aligned.
However, pregnancy can throw off this balance. Some common patterns include:
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Tight or overactive pelvic floor muscles that restrict movement and create tension through the SI joints.
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Weak or underactive pelvic floor and core muscles that allow too much movement and lead to joint instability.
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Asymmetrical muscle activation, often from favoring one side, standing with weight shifted to one hip, or carrying a toddler on one side.
A pelvic health physical therapist can assess which pattern applies to you and tailor exercises accordingly.
Posture and Alignment Changes
As your belly grows, your center of gravity shifts forward. To compensate, many pregnant people begin to:
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Arch their lower back more (anterior pelvic tilt)
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Stand with knees locked or feet turned out
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Tuck the pelvis under while sitting
These postural changes alter how forces move through the pelvis and can place uneven stress on the SI joints. Over time, that can lead to irritation or inflammation.
A physical therapist can teach you how to adjust your posture safely, often with just small tweaks to how you stand, sit, and move.
What You Can Do to Help
Here are a few key strategies that can make a real difference:
1. Gentle Core and Pelvic Floor Activation
Learning how to engage your deep core and pelvic floor together, without over-tightening, is one of the most effective ways to stabilize the SI joints.
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Try diaphragmatic breathing: Inhale into your ribs and belly, let your pelvic floor gently lengthen; exhale and gently lift your pelvic floor while drawing your belly in.
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Avoid “bracing” or sucking in your stomach. The goal is coordinated, dynamic support, not stiffness.
2. Glute Strengthening
Strong glutes are your SI joint’s best friends. Simple exercises like:
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Clamshells (with a mini band)
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Bridges (with a gentle pelvic tilt)
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Side steps or monster walks
can help provide stability to the pelvis and reduce pain.
3. Postural Awareness and Movement Modifications
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When getting out of bed, roll to your side first, then push up with your arms instead of sitting straight up.
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Avoid standing on one leg to dress; sit down instead.
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When standing, keep weight evenly distributed between both legs.
4. Support Belts and Taping
A pelvic support belt can help offload pressure from the SI joints by providing gentle external stability. Some women also find relief with kinesio taping applied by a trained therapist.
5. Hands-On Physical Therapy
Manual therapy can help realign the pelvis, release tight muscles, and improve joint mobility. A pelvic health PT can also use gentle techniques to retrain the muscles around the SI joints for better support.
The Bottom Line
SI joint pain during pregnancy is incredibly common, but it’s not something you just have to “put up with.” Understanding the role of hormones, posture, and pelvic floor function can help you take control and move through pregnancy with greater comfort and confidence.
If you’re experiencing persistent pain, especially one-sided or radiating discomfort, reach out to a pelvic health physical therapist. With the right guidance, you can reduce pain, improve stability, and prepare your body for a smoother pregnancy and postpartum recovery.
If you’re struggling with any pregnancy or postpartum concerns and want a personalized evaluation and treatment plan, make an appointment with one of the Pelvic Floor Physical Therapists at The Pelvic Health Center in Madison, NJ. We’re trained to help identify and treat the causes of your incontinence!