Your back has hurt for two years. Three doctors told you three di%erent things. Disc. Glute. Hip flexor. You did PT for both. You got a cortisone shot in the SI joint. You felt better for six weeks. Then you didn’t. Nobody can tell you why it keeps coming back.
If the cortisone shot helped for six weeks, your SI joint is probably the answer. Here is what most providers miss about SI joint pain — and what we do at Dynamic Athlete that breaks the recurrence pattern.
The SI joint is the most under-diagnosed cause of low back pain
The sacroiliac joint is where your sacrum — the base of your spine — meets your pelvis. There are two of them, one on each side. They are designed for stability, not motion. They transfer load between your spine and your legs.
SI joint pain accounts for somewhere between fifteen and thirty percent of chronic low back pain cases, depending on which study you read. It is consistently under-diagnosed because the pain pattern overlaps with disc problems, hip problems, piriformis syndrome, and glute pain. Patients are often worked up for everything else before someone thinks to check the SI joint.
How do we know it’s the SI joint? Specific physical exam maneuvers — FABER test, Gaenslen test, distraction test, compression test, thigh thrust. If multiple of these reproduce your exact pain, the SI joint is the likely source. The diagnostic gold standard is a fluoroscopicallyguided SI joint injection: if numbing the joint resolves the pain for the duration of the local anesthetic, it confirms the SI joint as the pain generator.
Why the cortisone wore off?
Cortisone calms inflammation. That’s its job and it does it well. But SI joint dysfunction is usually not primarily inflammatory — it’s mechanical. The joint surfaces are irritated. The ligaments that hold the joint together — the posterior sacroiliac ligament, the sacrotuberous ligament, the sacrospinous ligament — are loose, lax, or damaged. That mechanical instability is what’s driving your pain, and cortisone does nothing for it.
This is especially common after pregnancy. Pregnancy stretches the SI joint ligaments to accommodate delivery, and many women never recover the original tension. The joint moves more than it should, the joint surfaces grind, the surrounding muscles spasm to try to stabilize it, and chronic pain sets in. This pattern is one of the most underrecognized contributors to postpartum chronic back pain.
“Cortisone treats the inflammation. PRP treats the joint and the ligaments. Different problems, different tools.”
What PRP plus Shockwave actually does for the SI joint?
For an SI joint that has been confirmed as your pain generator and has failed conservative care including cortisone, the regenerative protocol I use is this:
One: Ultrasound-guided PRP injection into the SI joint itself and into the surrounding posterior ligament complex. We use multi-spin leukocyte-rich PRP for the ligaments — they need a different prep than the joint surface itself, which gets leukocyte-poor PRP. The combination addresses both the joint surface and the lax ligaments that are letting the joint move too much.
Two: Dynamic Shockwave around the SI joint complex. Focused ESWT into the posterior ligament tissue. EMTT across the broader region to drive deeper cellular response. This combination accelerates ligament remodeling so the joint becomes more stable over the months following injection.
Three: A specific PT program targeting deep core, gluteus medius, and pelvic floor stability. Generic core work doesn’t address SI joint instability. We refer to PTs in Boulder, Longmont, and Lafayette who specialize in this.
I perform the injection myself, under ultrasound, in our office. Some clinics send patients to a pain specialist for the injection. I do it directly because precision matters here — the SI joint is anatomically variable and the ligament targets are specific.
How long until it works?
Most patients notice meaningful change at six to eight weeks. The PRP needs time to do its biological work. The ligament remodeling continues for three to six months. Patients on the combined Shockwave-plus-PRP protocol get there up to fifty percent faster than patients on PRP alone.
For straightforward SI joint cases, we usually do one PRP procedure and three to four shockwave sessions. For more complex cases — significant ligament laxity, multiple prior procedures, postpartum patients with severe instability — we sometimes do a second PRP injection at the twelve-week mark.
90%+ SI JOINT PATIENTS REPORT 75%+ IMPROVEMENT
15-30% OF CHRONIC LOW BACK PAIN IS THE SI JOINT — AND MISSED
What we won’t do?
If you have severe SI joint degeneration with bone-on-bone changes on imaging, the regenerative option is less effective and I’ll send you for a surgical SI joint fusion consult with the right surgeon. If you have an underlying spondyloarthropathy — an inflammatory arthritis that mimics SI joint dysfunction — we coordinate with rheumatology. If your pain is actually coming from your hip or your lumbar discs and the SI joint diagnosis was wrong, we identify that on the evaluation and pivot.
The most important visit is the first one. We get the diagnosis right before we treat.
Cost against years of dysfunction
You’ve already invested in PT, cortisone, imaging, and probably some specialist consults. Total that up and most patients are three to six thousand dollars into a problem they still have. The regenerative protocol is comparable in cost — but it actually ends the cycle. Cherry financing spreads the investment over months at 0% APR. Insurance does not cover the procedure.
The real comparison is what your life looks like with versus without this pain for the next ten years. If you’re a postpartum mother who can’t pick up your toddler without bracing your back, or an active fifty year old who’s stopped hiking because the SI joint pain ruins the next day, the calculation gets simple.
What patients ask before booking!
How do I know my pain is the SI joint and not my low back?
The physical exam is the start. Specific tests reproduce the pain when the SI joint is the source. If we’re not certain, we can do a diagnostic injection — if numbing the joint resolves the pain temporarily, we have our answer.
I’ve had two cortisone shots. Can I still get PRP?
Yes. We typically want eight to twelve weeks between the last cortisone and the PRP because cortisone can affect the local biology. We plan the timing on the evaluation.
Is this safe during postpartum recovery?
Yes. We commonly treat postpartum patients with SI joint instability. Some considerations around breastfeeding timing — we walk through those.
Is the injection painful?
There’s discomfort during the injection itself, kept brief by local anesthesia and ultrasound precision. The two days after are sometimes more sore than the joint was before — that’s expected and resolves quickly.
Do I need surgery if PRP doesn’t work?
SI joint fusion is a real surgery for failed conservative cases, but it’s not a small operation. We exhaust the regenerative options first. Most patients don’t need surgery