That Hip and Low Back Pain You Keep Ignoring? It Might Be Your SI Joint.
Published: April 10, 2026 | By Dr. Kelly Frank, DPT
You know that deep, nagging ache on one side of your lower back or into your buttock? The one that flares when you roll over in bed, climb stairs, or sit too long? A lot of people write that off as a “hip thing” or just tight muscles. But there’s a good chance it’s your sacroiliac (SI) joint — and there’s an even better chance your pelvic floor is involved.
What Is the SI Joint — and Why Does It Matter?
Your sacroiliac joints sit where your sacrum (the triangular bone at the base of your spine) meets your iliac bones (your hip bones) — one on each side of your pelvis. They transfer weight between your upper body and your legs, absorbing shock and providing stability during everyday movement. When the SI joint becomes irritated, too loose, or too restricted, it can cause pain that radiates into the low back, buttocks, groin, and even down the leg — and it’s one of the most commonly misdiagnosed sources of pain, often confused with a disc problem, sciatica, or general hip pain.
The Pelvic Floor Connection Nobody Talks About
Here’s what makes SI joint dysfunction tricky: it rarely exists in isolation. Your pelvic floor muscles attach directly to the bones that form the SI joint — the pubic bone, the tailbone, and the ilium. When the pelvic floor is too tight, it can pull the pelvis out of alignment and compress the SI joint. When it’s too weak, the SI joint loses crucial stability and starts to overwork. Either way, pain follows.
This is exactly why at Frankly Pelvic, our approach to sacroiliac and hip dysfunction always includes assessing the pelvic floor — not just the joint itself.
Signs It Might Be Your SI Joint
- Pain or aching on one side of the low back or deep in the buttock
- Discomfort that worsens when rolling over in bed, getting in and out of a car, or climbing stairs
- A feeling of instability or “giving way” when walking
- Pain that flares with prolonged sitting, then eases when you move around
- Symptoms that started or worsened during or after pregnancy
That last one is especially common. Pregnancy hormones increase joint laxity throughout the pelvis — which is necessary for birth, but can leave the SI joint vulnerable long after delivery.
How We Treat It at Frankly Pelvic
At Frankly Pelvic, we take a head-to-toe approach to sacroiliac and hip dysfunction. That means looking at your posture, how you walk, how your core and pelvic floor activate during movement, and where the real imbalances are hiding. Treatment may include manual therapy to restore joint mobility, targeted strengthening for the pelvic floor and deep core, movement retraining so your body stops compensating, and postural support while strength builds back up.
The goal isn’t just pain relief — it’s getting you back to lifting, walking, exercising, and living without bracing yourself for the next flare.
Do You or Someone You Know Struggle With Hip or SI Joint Pain?
If you or someone you love has been dealing with stubborn hip or low back pain — especially pain that hasn’t improved with stretching, chiropractic care, or traditional PT — it may be time to look at the full picture. The pelvic floor piece is often exactly what’s missing.
Ready to Take the Next Step?
Do you or someone you know struggle with hip, SI joint, or pelvic pain? You don’t have to keep guessing what’s going on. I’d love to connect, answer your questions, and talk through how pelvic floor physical therapy might help. Reaching out is the first step — and it’s a free one.
I see patients in Winter Park and Altamonte Springs, FL, and also offer mobile in-home and virtual sessions throughout Florida.
Schedule Your Free Discovery CallDr. Kelly Frank is a Doctor of Physical Therapy and pelvic health specialist at Frankly Pelvic, serving patients in Winter Park and Altamonte Springs, FL — in-office, mobile, and virtually.
