The Straight leg raise is a neurodynamic passive test that aids in assessing the integrity of the spinal cord and its meninges by stressing the sciatic nerve, lumbar region and associated discs/segments using the lower limb as a lever.
With the patient lying supine, the examiner passively;
1. Internally rotates and slightly adducts the patients leg while maintaining knee extension (straight leg).
2. The leg is raised (hip flexion) by the examiner by holding the area of the Achilles tendon.
3. The examiner must be careful to monitor any signs of pain.
If required sensitising methods such as ankle dorsi-flexion and neck flexion can be introduced to increase potential for irritation.
Another variation is to take the straight leg to its maximum flexion as determined by the patient’s physique then lower it again only by 2-3 cm and then apply dorsiflexion to elicit pain.
Yet another addition to this test, when the leg is fully raised, is to apply pressure into the popliteal fossa thereby tensing the sciatic nerve and observe for signs of pain. Use one hand to raise the leg and the other to apply pressure with your thumb in the popliteal fossa.
The straight leg raise is considered positive if the patient exhibits an aggravation in symptoms, neurological signs, or radicular pain.
Sensitising factors can also aid in understanding the underlying pathology.
Noting the degree at which the symptoms commence during the test can help assess the progress of the patient.