Characteristics, Distribution and Behavior of Sensory Responses of the Straight Leg Raise Test in Asymptomatic Individuals

Objectives: The purpose of our study was to examine the characteristics, distribution, and behavior of sensory responses of the straight leg raise (SLR) test in asymptomatic individuals. We hypothesized that: ï‚Ÿ The sensory response would be along the sciatic nerve distribution and its distal tributaries ï‚Ÿ No significant difference in sensory response would exist between limbs.

Method: The range of motion (ROM), quality, quantity, and distribution of sensory responses were measured in 47 asymptomatic individuals during the SLR test. Passive ankle dorsiflexion and passive neck flexion were used as neural sensitizing maneuvers.

Results: The mean ± SD ROM for passive terminal hip flexion was 81 ± 18.5° and 80 ± 17.8° for left and right hips, respectively. All sensory responses experienced were along the sciatic nerve distribution. The mean ± SD of all sensory responses for the left and right lower extremities were respectively as follows: stretching was 6.25 ± 1.75 and 6.63 ± 2.09 cm (p=0.11); burning was 4.28 ± 3.07 and 6.70 ± 5.39 cm (p=0.15); tingling was 2.65 ± 3.06 and 2.63 ± 3.05 cm (p=0.98); and numbness was 2.80 ± 0.14 and 0.60 ± 0.14 cm (p=0.06).

Conclusion: There are no significant differences in sensory response between limbs during the SLR test in asymptomatic individuals. Sensory responses were along the sciatic nerve distribution and its distal tributaries. These responses were intensified with the addition of passive ankle dorsiflexion suggesting it is an effective neural sensitizing maneuver when performing the SLR test.