The Straight-Leg Raising test can detect abnormal neurodynamics
Tests the mobility of the dura matter from the forth lumbar level downwards. It also tests the mobility of the fourth and fifth lumbar nerve roots, and the intraspinal extent of the first and second sacral nerve roots.
It remains a valid test only so long as the dura matter and its investment of the nerve roots retain sensitivity.
Tension through the structure on the L5 and/or S1 nerve root. The SLR my produce leg pain by stretching the nerve root