SI Joint Pain During Pregnancy: Causes, Symptoms, and Safe Exercises

Lower back pain is one of the most common complaints during pregnancy. If you’ve ever felt soreness in the dimples at the base of your back - those small indentations right above your buttocks - your sacroiliac (SI) joint may be involved. This joint is often overlooked because it doesn’t get the same attention as the spine or hips, but it plays a critical role in stability, movement, and how your body handles daily activities. Understanding the SI joint and how to support it can help you reduce discomfort and stay active safely during pregnancy.

What Is the SI Joint?

The sacroiliac (SI) joint connects your sacrum - the triangular bone at the base of your spine - to your iliac bones, which are the large bones on either side of your pelvis. You have two SI joints, one on each side of your sacrum, and they’re designed to transfer forces between your spine and legs. In other words, this little joint is the cornerstone of your body.

Every step you take, every hop, every time you lift a child or carry groceries, your SI joint absorbs significant impact. It’s built for stability, not for large movements, which is why we rarely think about it until it starts to hurt.

Normally, the SI joint is very stable. It doesn’t move much, but the ligaments and surrounding muscles help it act as a shock absorber. Unfortunately, there are several common factors that can disrupt this stability, especially during pregnancy:

• Hormonal changes: Pregnancy hormones, like relaxin, loosen the ligaments around your pelvis. While this helps prepare your body for birth, it also allows more mobility in the SI joint, which can lead to discomfort.

• Falls or impacts: Landing hard on your knees or bottom can jolt the SI joint out of alignment. Even a seemingly minor fall can cause irritation or pain.

• Repetitive rotational movements: If you’re a golfer or love rotational sports (or maybe just twisting your body repeatedly while playing with the kids - same thing!), your SI joint takes repeated stress. Golfers, I’m looking at you - those swings add up!

Interestingly, no muscles attach directly to the SI joint, which makes it a little tricky to “strengthen” or rest directly. That’s why we focus on the muscles around it, particularly your diaphragm, core, glutes, and pelvic floor - to support proper function and reduce discomfort.

Why the Diaphragm, Core, and Pelvic Floor Are So Important

Your diaphragm helps control intra-abdominal pressure, which stabilizes your spine from above. Your core, including the deep abdominal muscles like the transversus abdominis, stabilizes your spine from the front and sides. And your pelvic floor acts like a support hammock beneath your pelvis, controlling motion and supporting the weight of your uterus during pregnancy.

When these three systems work together, they create a dynamic support network around your SI joint. Weakness, disconnection, or poor coordination in any of these areas can overload the SI joint, leading to pain and discomfort.

Think of it like this: the SI joint is the cornerstone of your house. If the scaffolding around it (your diaphragm, core, and pelvic floor isn’t strong), the cornerstone takes more stress. Strengthen the scaffolding, and the joint can absorb force safely.

How to Recognize SI Joint Pain

SI joint pain often presents as:

• Pain in the dimples of your lower back (the two small indentations just above your buttocks).

• A nagging pain that may radiate into the buttocks, hips, or groin, but usually not down the leg like classic sciatica.

• Discomfort during single-leg stance or when standing on the affected side.

• Sensitivity during activities that involve twisting, bending, or lifting.

It’s important to note that SI joint dysfunction is a diagnosis of exclusion. Many other sources can cause lower back pain, including your lumbar spine, hip joints, or even muscular imbalances. A physical therapist can help determine if your SI joint is truly the source and guide you toward safe exercises.

Safe Exercises for Supporting the SI Joint

Even if you’re not sure exactly what’s causing your pain, there are several gentle, pregnancy-safe exercises that support the muscles around the SI joint. These exercises focus on core, glute, and pelvic floor engagement, helping your SI joint absorb forces without direct stress.

1. 360° Diaphragmatic Breathing

• Sit or lie comfortably.

• Inhale fully, expanding your ribs, belly, and back in all directions.

• Exhale slowly, gently engaging your pelvic floor and drawing your core inward.

• Repeat 4-5 breaths. Focus on connection and control, not effort.

This exercise helps coordinate your diaphragm, core, and pelvic floor, giving your SI joint support from all directions.

2. Glute Bridge

• Lie on your back with knees bent, feet hip-width apart.

• Exhale, engage your core, and lift your hips toward the ceiling.

• Hold for 2–3 seconds, then lower slowly.

• Repeat 10–12 reps.

Glute bridges strengthen your posterior chain, including your glutes and hamstrings, which help stabilize your pelvis and reduce SI joint strain.

3. Hip Adduction Isometric in Hook Lying

• Lie on your back with knees bent and feet flat on the floor (hook lying).

• Place a small pillow or ball between your knees.

• Exhale, gently squeeze your knees together, engaging your inner thighs and core.

• Hold 5 seconds, then release. Repeat 8–10 reps.

This simple exercise activates your inner thigh muscles and core, promoting stability and alignment in your pelvis and SI joint without aggressive movement.

Bottom Line

The SI joint may be small, but it’s a cornerstone of your body - especially during pregnancy. Hormonal changes, falls, and repetitive movements can disrupt its stability, leading to pain. While there’s no direct way to “rest” this joint, supporting the surrounding muscles — your diaphragm, core, pelvic floor, and glutes — can make a significant difference.

Exercises like 360° breathing, glute bridges, and hip adduction isometrics are generally safe and effective, even if you’re not sure of the exact cause of your pain. These movements help you reconnect with your core, strengthen your support system, and reduce stress on the SI joint.

And remember: SI joint dysfunction is a diagnosis of exclusion. A physical therapist can help identify the true source of your pain and guide you safely through exercises, ensuring you stay strong, stable, and comfortable throughout your pregnancy.