Ruling Out the SI Joint: The McKenzie Method Explained
If you’ve ever had nagging low back or hip pain, you may have wondered if your sacroiliac (SI) joint is the culprit. The SI joint connects the sacrum (the base of your spine) to the ilium (part of your pelvis). It plays a key role in transferring weight between your upper body and your legs, acting like a shock absorber.
Some people are convinced right away that their SI joint is the problem. I once had a friend who insisted their pain had to be coming from the SI joint because “someone told me that’s what it always is.” But when we look at the research, the chances are actually quite low. SI joint dysfunction is a real condition, but it’s much less common than people think — and there are many other, more likely sources of back pain.
This is where the McKenzie Method, combined with other evidence-based tools, gives physical therapists a structured way to narrow down what’s really happening.
Why SI Joint Pain Is Less Likely
Although the sacroiliac joint can cause pain, research shows that only about 10–25% of people with low back pain actually have SI joint dysfunction.² In other words, it’s the minority cause.
When the SI joint does refer pain, it follows fairly recognizable patterns. Studies consistently show that pain is most often felt in the buttock and lumbosacral region, and only rarely extends below the knee:
Sacroiliac Joint Referred Pain Distribution
(percentages vary slightly across studies)
Referral Region | Approx. % of Patients |
|---|---|
Buttock (ipsilateral) | ~94% |
Low back (PSIS / lumbosacral area) | ~72% |
Posterior thigh | ~50% |
Lateral Thigh | ~28% |
Groin | ~14% |
Calf (below knee) | <10 (rare)% |
Foot | Very rare (<5%) |
This means that while SI joint pain can sometimes radiate into the thigh or groin, true pain that goes into the calf or foot is extremely rare. More often, symptoms in those areas point toward lumbar disc or nerve root involvement rather than the SI joint.
By comparison, most back pain comes from other, more common sources, such as:
Because these conditions are so much more common, clinicians are cautious about diagnosing SI joint dysfunction too quickly.
How the McKenzie Method Works
The McKenzie Method (also known as Mechanical Diagnosis and Therapy, or MDT) was developed by physiotherapist Robin McKenzie. It’s widely used around the world to evaluate and treat back and neck pain.
Here’s how it helps in suspected SI cases:
- 1Assessment through movement – Patients perform repeated movements like bending forward, arching backward, or side-gliding. The therapist observes whether symptoms improve, worsen, or move to a different location.
- 2Centralization vs. peripheralization – If pain moves toward the spine (centralizes), it strongly suggests the lumbar spine is the source. If pain spreads farther away (peripheralizes), the therapist takes note and adjusts the evaluation.
- 3Ruling out the spine first – Because the lumbar spine accounts for so many cases of low back and hip-area pain, McKenzie-trained therapists want to rule this out before assuming the SI joint is at fault.
- 4Creating a treatment plan – If the spine is the driver, targeted exercises (often repeated extension or side-gliding) can reduce or eliminate symptoms. If the spine is not involved, the therapist then considers the SI joint or other causes.
The Role of Laslett’s Provocation Tests
Even if the spine is ruled out, physical therapists don’t jump straight to “it’s definitely the SI joint.” That’s where the research of Dr. Mark Laslett comes in.
Laslett developed a cluster of provocation tests — physical maneuvers designed to reproduce SI joint pain by stressing the joint. These include:
Research shows that if at least three out of these five tests are positive, the likelihood of SI joint dysfunction being present increases significantly.³
Still, these tests are not perfect — which is why Aprill’s work on diagnostic injections remains so important when there is uncertainty.
Thigh Thrust Test
Compression Test
Sacral Thrust Test
Gaenslen Test
Distraction Test
What an Evaluation Might Look Like
If you come to a physical therapist with suspected SI joint pain, here’s a typical process:
- 1History Taking – When did the pain start? What makes it better or worse? Any trauma or repetitive activity involved?
- 2Movement Testing (McKenzie) – You’ll perform repeated movements. The therapist observes whether pain changes location or intensity.
- 3Pattern Recognition – Centralization of pain points to the spine. Lack of change may suggest other sources.
- 4Provocation Testing (Laslett cluster) – If the spine is ruled out, the therapist stresses the SI joint through specific maneuvers.
- 5Referral if Needed – If uncertainty remains, a physician may order a diagnostic SI joint injection. Relief following the injection confirms the diagnosis.
- 6Treatment Plan – Depending on findings, treatment may include McKenzie-based spine exercises, core stabilization, manual therapy, or SI-specific stabilization strategies.
Why This Matters for Patients
Too often, people latch onto a diagnosis like “SI joint pain” without a clear process to confirm it. This can lead to treatments that don’t actually solve the problem. By using the McKenzie Method first, then layering in Laslett’s tests, and finally understanding the role of injections from Aprill’s work, clinicians can make more accurate diagnoses — and patients can get the right treatment sooner.
The bottom line? Most back and hip pain isn’t from the SI joint. A structured, step-by-step approach prevents misdiagnosis and wasted time.
Final Thoughts
Back pain can be frustrating and sometimes scary. But the good news is, physical therapists have reliable methods to identify where the pain is truly coming from. The McKenzie Method provides a structured way to test the spine first, Laslett’s cluster helps screen the SI joint, and Aprill’s research shows how injections can confirm the diagnosis when needed.
If you’re struggling with persistent back or hip-area pain, don’t assume it’s the SI joint — or the disc, or arthritis — without a proper evaluation. A McKenzie-trained physical therapist can guide you through the process, helping you find answers and a plan that actually works.
References
- 1McKenzie R, May S. The Lumbar Spine: Mechanical Diagnosis & Therapy. Spinal Publications New Zealand Ltd; 2003.
- 2Cohen SP. Sacroiliac joint pain: a comprehensive review of anatomy, diagnosis, and treatment. Anesth Analg. 2005;101(5):1440–1453.
- 3Laslett M, Aprill CN, McDonald B, Young SB. Diagnosis of sacroiliac joint pain: validity of individual provocation tests and composites of tests. Man Ther. 2005;10(3):207–218.
- 4Vleeming A, et al. The sacroiliac joint: an overview of its anatomy, function, and potential clinical implications. J Anat. 2012;221(6):537–567.
- 5Aprill C, Dwyer A, Bogduk N. The prevalence of asymptomatic zygapophysial joints demonstrated by controlled, diagnostic blocks. Spine. 1990;15(6):453–457.
Tom Willemann
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