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Home› Physical Therapy› Free Self-Checks› Special Tests› Lumbar Spine & SIJ

Lumbar Spine & SIJ Special Tests

Disc-related radiculopathy and sacroiliac joint provocation tests, including the Laslett cluster.

Reviewed by Dr. Richard Holsman, PT, DPT, NCS · Last reviewed November 13, 2026 · For clinician education

⚠️ For clinicians

For clinician education; special tests support but do not replace a full examination. This page is a reference for physical therapists, occupational therapists, athletic trainers, students and other clinicians. Patients with joint or spine pain should be examined by a licensed clinician.

Screen for red flags (cauda equina signs, fracture, cancer, infection) before provocation testing. For SIJ pain, single tests are weak; the Laslett cluster is the best supported approach.

On this page

Accuracy at a glance

TestTarget conditionSnSp+LR−LRSource
Straight leg raiseDisc herniation, surgical populations (pooled) (+ more below)92%28%——[1]
Crossed straight leg raiseDisc herniation (pooled)28%90%——[1]
Slump testLumbar disc herniation (single study)84%83%——[2]
SIJ distraction testSIJ pain (anesthetic injection reference)60%81%3.200.49[3]
Thigh thrust testSIJ pain (anesthetic injection reference)88%69%2.800.18[3]
SIJ compression testSIJ pain (anesthetic injection reference)69%69%2.200.46[3]
Sacral thrust testSIJ pain (anesthetic injection reference)63%75%2.500.50[3]
Gaenslen’s testSIJ pain, right side (anesthetic injection reference) (+ more below)53%71%1.840.66[3]

Sn = sensitivity, Sp = specificity, LR = likelihood ratio. A dash means the source we checked did not report that value.

How to read the accuracy numbers

  • Sensitivity: of people who have the condition, the share with a positive test. A highly sensitive test that is negative helps rule the condition out.
  • Specificity: of people without the condition, the share with a negative test. A highly specific test that is positive helps rule it in.
  • Positive likelihood ratio (+LR): how much a positive result raises the odds. About 5–10 is a moderate shift; above 10 is large.
  • Negative likelihood ratio (−LR): how much a negative result lowers the odds. About 0.1–0.2 is a moderate-to-large shift; near 1 means little change.
  • Values depend on the study’s patients, examiners and reference standard. Many studies are small, so treat single-study numbers with caution.

Lumbar Spine & SIJ special tests, step by step

Each test is described in our own words. Compare with the uninvolved side and stop if the test provokes severe pain.

Straight leg raise

Also called: SLR, Lasègue test

Purpose
Tensions the sciatic nerve and lower lumbar nerve roots (L4–S1).
Patient position
Supine, head flat, both legs straight.
How to perform[5]
  1. Hold the heel and keep the knee straight.
  2. Slowly raise the leg with the hip in neutral rotation.
  3. At the onset of symptoms, note the angle and add ankle dorsiflexion or neck flexion to see if symptoms change.
Positive finding
Familiar leg pain (below the knee) between about 30° and 70° that increases with sensitizing moves. Hamstring tightness alone is not positive.

Diagnostic accuracy

Target condition (source)SensitivitySpecificity+LR−LR
Disc herniation, surgical populations (pooled)[1]92%28%——
Specificity varied widely (10–100%); results from imaging-based studies were more varied and less sensitive.
Lumbar disc herniation (single study)[2]52%89%——

Crossed straight leg raise

Also called: Well-leg raise

Purpose
Raising the unaffected leg pulls on the nerve roots of the affected side.
Patient position
Supine.
How to perform[5]
  1. Perform a straight leg raise on the pain-free leg.
Positive finding
Familiar pain in the affected leg.

Diagnostic accuracy

Target condition (source)SensitivitySpecificity+LR−LR
Disc herniation (pooled)[1]28%90%——
Rarely positive, but strong evidence for herniation when it is.

Slump test

Purpose
Progressively tensions the whole neuraxis and sciatic nerve.
Patient position
Sitting at the edge of the table, hands behind the back, thighs supported.
How to perform[5]
  1. Ask the patient to slump the trunk (round the back) while you keep the head neutral.
  2. Add neck flexion.
  3. Straighten the knee.
  4. Dorsiflex the ankle.
  5. Release the neck flexion and see if symptoms ease.
Positive finding
Familiar radicular symptoms that ease when the neck comes out of flexion.

Diagnostic accuracy

Target condition (source)SensitivitySpecificity+LR−LR
Lumbar disc herniation (single study)[2]84%83%——

SIJ distraction test

Also called: Gapping test

Purpose
Stresses the anterior sacroiliac ligaments.
Patient position
Supine, a small pillow under the knees.
How to perform[5]
  1. Cross your arms and place the heels of your hands on the medial side of both ASISs.
  2. Push down and outward (posterolaterally) for several seconds, building to a firm force.
Positive finding
The patient’s familiar buttock or low back pain.

Diagnostic accuracy

Target condition (source)SensitivitySpecificity+LR−LR
SIJ pain (anesthetic injection reference)[3]60%81%3.200.49
Most specific single test.

Thigh thrust test

Also called: Posterior shear test

Purpose
Applies a backward shear force to the sacroiliac joint through the femur.
Patient position
Supine.
How to perform[5]
  1. Flex the tested hip to 90° with the knee bent, slightly adducted.
  2. Place one hand under the sacrum to stabilize it.
  3. Push down along the line of the femur through the knee.
Positive finding
Familiar buttock pain on the tested side.

Diagnostic accuracy

Target condition (source)SensitivitySpecificity+LR−LR
SIJ pain (anesthetic injection reference)[3]88%69%2.800.18
Most sensitive single test.

SIJ compression test

Purpose
Compresses the sacroiliac joints from the side.
Patient position
Side-lying, hips and knees bent about 90°, painful side up.
How to perform[5]
  1. Place your hands on the top of the iliac crest.
  2. Push straight down toward the table for several seconds.
Positive finding
Familiar SIJ-area pain.

Diagnostic accuracy

Target condition (source)SensitivitySpecificity+LR−LR
SIJ pain (anesthetic injection reference)[3]69%69%2.200.46

Sacral thrust test

Purpose
Applies a forward shear force to the sacrum.
Patient position
Prone.
How to perform[5]
  1. Place the heel of one hand over the middle of the sacrum, the other hand on top.
  2. Push straight down (anteriorly) toward the table.
Positive finding
Familiar SIJ-area pain.

Diagnostic accuracy

Target condition (source)SensitivitySpecificity+LR−LR
SIJ pain (anesthetic injection reference)[3]63%75%2.500.50

Gaenslen’s test

Purpose
Applies a torsion force across the sacroiliac joint.
Patient position
Supine, close to the edge of the table.
How to perform[5]
  1. The patient hugs the knee of the leg farther from the edge to the chest.
  2. Let the leg nearest the edge hang off the table into hip extension and apply gentle overpressure down on that thigh.
Positive finding
Familiar SIJ-area pain.

Diagnostic accuracy

Target condition (source)SensitivitySpecificity+LR−LR
SIJ pain, right side (anesthetic injection reference)[3]53%71%1.840.66
SIJ pain, left side (anesthetic injection reference)[3]50%77%2.210.65
Gaenslen’s did not add to the cluster.

Test clusters and prediction rules

Combinations of findings usually shift probability more than any single test.

Laslett cluster: 2 of 4 tests

Items: Distraction, thigh thrust, compression and sacral thrust. Do distraction and thigh thrust first; stop once two are positive.

Accuracy: Sensitivity 88%, specificity 78%, +LR 4.00, −LR 0.16.[3]

Laslett cluster: 3 or more of 6 tests

Items: All six provocation tests (the four above plus right and left Gaenslen’s).

Accuracy: Sensitivity 94%, specificity 78%, +LR 4.29. When none of the six tests provoked familiar pain, the SIJ could be ruled out as the source in this sample.[3]

Flynn rule for success with spinal manipulation (treatment response, not diagnosis)

Items: Five findings: symptom duration, fear-avoidance beliefs, lumbar hypomobility, hip internal rotation range of motion, and no symptoms below the knee (cut-offs are in the full paper).

Accuracy: 4 of 5 present: +LR 24.38; probability of success rose from 45% to 95%. Derivation study.[4]

What we left out

Prone instability test and the Hicks stabilization rule (no verified accuracy numbers), FABER/Patrick’s for SIJ, femoral nerve tension test and the Flynn rule’s exact cut-offs are not shown. We only show accuracy numbers we could check against the original study or review.

Sources, review and disclosures

Graded citations

How we grade sources. A = systematic review or meta-analysis. B = single prospective diagnostic accuracy study. C = small, retrospective or case-control study, or a clinical prediction rule that has only been derived (not yet validated). D = expert clinical opinion (our test descriptions). Every accuracy number on this page was checked against the cited abstract or full text on November 13, 2026. If we could not check a number, we left it out and say “accuracy data not verified.”

  1. Grade A van der Windt DA, Simons E, Riphagen II, et al. Physical examination for lumbar radiculopathy due to disc herniation in patients with low-back pain. Cochrane Database Syst Rev. 2010;(2):CD007431. doi:10.1002/14651858.CD007431.pub2 (abstract). PubMed 20166095
  2. Grade B Majlesi J, Togay H, Ünalán H, Toprak S. The sensitivity and specificity of the Slump and the Straight Leg Raising tests in patients with lumbar disc herniation. J Clin Rheumatol. 2008;14(2):87-91. doi:10.1097/RHU.0b013e31816b2f99 (abstract). PubMed 18391677
  3. Grade B Laslett 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. doi:10.1016/j.math.2005.01.003 (Tables 2, 4 and 6; reference standard: SIJ anesthetic injection; 48 patients). PubMed 16038856
  4. Grade C Flynn T, Fritz J, Whitman J, et al. A clinical prediction rule for classifying patients with low back pain who demonstrate short-term improvement with spinal manipulation. Spine. 2002;27(24):2835-2843. doi:10.1097/00007632-200212150-00021 (abstract; derivation study). PubMed 12486357
  5. Grade D Holsman Physical Therapy clinical guidance. Patient position, test steps and positive findings written in our own words by Holsman physical therapists and reviewed by Dr. Richard Holsman, PT, DPT, NCS. Expert opinion, not a research source.

Reviewer

Reviewed by Dr. Richard Holsman, PT, DPT, NCS (Board-Certified Clinical Specialist in Neurologic Physical Therapy), founder of Holsman Physical Therapy. Last reviewed: November 13, 2026.

Change log

  • November 13, 2026: Page published. Test descriptions written in our own words; accuracy values checked against the cited sources.

Review policy

We re-check every number on this page against its source at least once a year, and sooner if a source is updated, a better study is published or a reader reports a problem. Changes are listed in the change log with the date. To report an error, contact us.

Licensing

Test descriptions, steps and the accuracy summaries are original text by Holsman Physical Therapy. Accuracy values are individual numbers cited with credit to the original studies; no tables, figures or text from journals, textbooks or other websites are reproduced. Linking to a source does not imply its endorsement. Demonstration videos, when added, will be filmed by Holsman physical therapists with consenting adult models.

Conflict of interest and advertising

This page is published by Holsman Physical Therapy and Wellness, P.C., which runs outpatient and in-home therapy practices; that is our only commercial interest. The page carries no advertising, no sponsorship and no affiliate links, and we received no payment from any source for it. Holsman Physical Therapy is not affiliated with the authors or publishers cited, and they do not endorse this website.

For clinician education; special tests support but do not replace a full examination. A positive or negative test changes the probability of a condition; it does not make a diagnosis. Interpret every result with the history, the rest of the examination, imaging when indicated, and clinical judgment. Stop any test that provokes severe pain or neurological symptoms.

Common Questions

What is the Laslett SIJ cluster?

Four pain provocation tests: distraction, thigh thrust, compression and sacral thrust. Two or more positive gave 88% sensitivity and 78% specificity (+LR 4.0, −LR 0.16) against an anesthetic SIJ injection in Laslett 2005.

Is the slump test more sensitive than the straight leg raise?

In Majlesi 2008 the slump test was more sensitive (84% vs 52%) and the straight leg raise slightly more specific (89% vs 83%) for lumbar disc herniation.

Referring a Patient?

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