One of the most common tests that I use to assess low back pain is the Straight Leg Raise, also know as the SLR or Lasegue Test. The patient lies on their back in a comfortable position and the examiner lifts the straight leg up, noting if or when it causes any symptoms into the lower back or back of the legs. These symptoms could be low back pain, muscle tightness in the legs, shooting/electric pain down the leg or a ‘pins & needles’ sensation. If pain is illicited, the leg is lowered slightly and then neck flexion and/or ankle dorsiflexion added. The leg can also be taken across the body to identify whether the sciatic nerve is implicated or it is just hamstring tightness.

As the nerve is stretched, tension first happens in the greater sciatic foramen, then over the ala of the sacrum and then the intervertebral foramen.

A device called a goniometer is used to measure the angle where the symptoms begin, which can help diagnose what the causes could be. Personally, I have an app on my iPhone which does the same job!

Interpreting the results

Shooting pain down the leg, pins & needles and/or numbness indicates involvement of neurological structures including the sciatic nerve (L4-S3) but doesn’t identify exactly where or how. Magee (1992) suggests:

• pain that increases with neck flexion and/or dorsiflexion indicates stretching of the dura mater of the spinal cord
• pain that does not increase with neck flexion indicates a lesion in the hamstring area, lumbosacral area (LSJ) or sacroliliac joint (SIJ)
• 35-70 degrees is most likely to present as nerve root stretch across posterior IV disc
• nerve root stretching finishes around 70 degrees so pain after 70 degrees is likely to be LSJ or SIJ
• 80-90 degrees of flexion is considered normal
• pain primarily in the back = central lesion
• pain in lower back and posterior leg = intermediate lesion
• posterior leg pain primarily = lateral lesion

References

Magee (1992) Orthopaedic Physical Assessment, 2^nd Ed. Philadelphia: W B Saunders Company. p267-269