Test: Prone Lumbar Instability Test

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Background/Purpose

The Prone Lumbar Instability Test, also known as the Prone Instability Test or the H and I Stability Test, is a clinical assessment tool designed to identify lumbar segmental instability in patients with low back pain. Developed by Hicks et al., this test evaluates the dynamic stabilization capacity of the lumbar spine musculature, particularly the deep spinal stabilizers including the multifidus, transversus abdominis, and other paraspinal muscles. Lumbar instability refers to the loss of the spine's ability to maintain its normal movement patterns under physiological loads, resulting in pain, neurological compromise, or deformity. This condition may result from degenerative disc disease, spondylolisthesis, ligamentous laxity, facet joint degeneration, or muscular dysfunction. The test is based on the principle that when the lumbar spine is unsupported, unstable segments will be painful with provocation, but when the spine is stabilized through muscular activation, the pain should decrease or resolve. This test has been shown to have good specificity for identifying patients who may benefit from lumbar stabilization exercises and is commonly used in physical therapy and sports medicine settings.

Procedure

Patient Position:
The patient lies prone (face down) on the examination table
The patient's body should be positioned so that the legs hang off the edge of the table from approximately mid-thigh or the level of the anterior superior iliac spines (ASIS)
The trunk remains on the table while the legs are unsupported
Arms can be positioned comfortably at the sides or overhead
The patient should be completely relaxed initially

Procedure:
Phase 1 - Passive Testing (Muscles Relaxed):
Initial Positioning: Ensure the patient is positioned with legs hanging off the table and completely relaxed
Posteroanterior (PA) Pressure: The examiner applies posteroanterior (downward) pressure through the spinous processes of the lumbar vertebrae, testing each level from L1 to S1

Use the heel or pisiform bone of your hand
Apply firm, oscillating pressure in a posterior-to-anterior direction
Test each spinal segment systematically

Symptom Assessment: Ask the patient to report any pain provocation at each level
Note which level(s) reproduce the patient's familiar pain
Document the location and intensity of symptoms
A segment is considered symptomatic if PA pressure reproduces pain

Phase 2 - Active Muscle Stabilization:
Muscle Activation: Instruct the patient to actively lift both legs off the floor (or extend the hips) while keeping the legs straight or slightly bent
This action activates the lumbar stabilizing musculature
The patient should maintain this position throughout retesting

Repeat PA Pressure: While the patient maintains active hip extension and muscular stabilization, repeat the posteroanterior pressure testing at the previously painful segment(s)
Compare Response: Assess whether the pain:

Decreases significantly or resolves (positive test)
Remains unchanged (negative test)
Increases (negative test)

Important Notes:
The patient must be able to adequately activate stabilizing muscles for valid results
The test relies on the comparison between relaxed and contracted states
Some variations have the examiner support the patient's legs rather than having the patient actively lift them
Performed: Bilaterally

Dialog

The patient lies prone with legs hanging off the table while the examiner applies posteroanterior pressure to lumbar segments; pain that occurs when muscles are relaxed but decreases with active muscle stabilization indicates lumbar instability.

Criteria

• No pain in relaxed state
• No reduction in pain with muscle activation
• No pain difference with change in phases
• No segmental specification

Measurement

LOINC Code

Scale/Grading

selection range; grade - LOINC ID
Option - Value option selection range; grade - LOINC IDPass ; Pass - Fail ; Fail -