Straight Leg Raise Test 3 – Sural Nerve Bias

Purpose of Straight Leg Raise Test 3 – Sural Nerve Bias: To test if a modified straight leg raise test with a bias towards the sural nerve assists in the differential diagnosis of sural nerve pathology in people with neurologic symptoms associated with radiculopathy (1).

Patient position: Supine lying.

Examiner position: Standing beside the patient, at the side of the limb to be tested.

Procedure: Perform the limb/joint positioning sequence in the following order:

1. Neutral alignment at the cervical, thoracic and lumbar spine, while the patient is on supine lying.
2. Hip flexion and adduction (to the end of the available range or until the patient reports radicular symptoms), having the knee at full extension (with the examiner’s one hand holding the anterior aspect of the patient’s distal thigh and the other hand holding the posterior aspect of the patient’s ankle)
3. Lower the leg slowly until the radicular symptoms are relieved and hold the leg at this level.
4. Sensitizing position: (a) ankle dorsiflexion (1-3), (b) cervical spine flexion, and/or (c) foot inversion (4). The return of radicular symptoms during ankle dorsiflexion, cervical spine flexion, and/or foot inversion with/without further straight leg raise (hip flexion (1)) indicates a positive test.

Alternative Procedure

In a cadaveric study, the following movement sequence was performed in supine in order to bias the test toward the sural nerve (1). In the first stage, the ankle was moved from plantar flexion into maximal dorsiflexion while the hip was maintained in a neutral position.

In the second stage, the hip was flexed to the available range of motion while the ankle was maintained in maximal dorsiflexion. In this study, ankle inversion was not included in the test due to the restricted ankle range of motion (1).

Outcome: This test is positive if (a) the limb/joint positioning sequence reproduces symptoms associated with radiculopathy, (b) the sensitizing position reproduces symptoms, and (c) there is a repeatable and measurable asymmetry between both sides along with the reproduction of symptoms.

Reference:

1. Coppieters MW, Crooke JL, Lawrenson PR, Khoo SJ, Skulstad T, Bet-Or Y. A modified straight leg raise test to differentiate between sural nerve pathology and Achilles tendinopathy. A cross-sectional cadaver study. Manual therapy. 2015;20(4):587-91.
2. Coppieters MW, Alshami AM, Babri AS, Souvlis T, Kippers V, Hodges PW. Strain and excursion of the sciatic, tibial, and plantar nerves during a modified straight leg raising test. Journal of Orthopaedic Research. 2006;24(9):1883-9.
3. Boyd BS, Topp KS, Coppieters MW. Impact of movement sequencing on sciatic and tibial nerve strain and excursion during the straight leg raise test in embalmed cadavers. The Journal of orthopaedic and sports physical therapy. 2013;43(6):398-403.
4. Magee DJ. Orthopedic Physical Assessment: Elsevier Health Sciences; 2013.