The role of an active muscular subsystem in prone instability test during rest and leg raise conditions.
Soniya Maharjan, Khin W Thu, Sasithorn Kongoun and 3 others
PMID 37497551WHAT IT FOUND
In 33 adults with long-standing low back pain, posterior-anterior spine displacement was reduced during leg raise at L1-L4 but not L5.
Sex did not change displacement, so prone instability test results should not be read differently for men and women.
Key findings
01PA displacement differed significantly between rest and leg raise at L1 to L4, but not at L5.
02At rest, PA displacement gradually decreased from L1 to L5.
03Sex did not significantly affect PA displacement across levels or between rest and leg raise.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study was cross-sectional and measured displacement only when participants were pain-free, so it does not tell you what happens when pain is present. No healthy comparison group was included, so the displacement patterns cannot be judged against typical spinal movement. The protocol used a fixed 100 N force and a fixed leg-raise height, which may not match how clinicians perform the test. Participants with BMI greater than 30 kg/m2, specific low back conditions, red flags, and adults older than 40 were excluded, so results should not be applied to them. The sample was recruited from a physical therapy faculty and surrounding areas and included only 33 participants.
Declared interests
The authors reported no conflict of interest with any financial organization. Funding came from the National Research Council of Thailand and the Faculty of Physical Therapy, Mahidol University.
The easy way to misread this
Do not conclude that the prone instability test diagnoses lumbar instability or that leg raise training improves stability. The study measured displacement during a test, not muscle strength, pain, function, or treatment response, and it did not compare healthy individuals.