The active straight leg raise test (ASLR) is a loading test which is used to assess pain provocation and the ability to load the pelvis through the limb. It is performed in lying and the patient is instructed to lift the leg 20cm off the bed (Mens, et al., 2001).

A positive response is a complete inability to lift the leg off the bed, however this response can vary from a slight difference in heaviness to complete inability. Mens and colleagues use a six-point scale to rate the level of difficulty: "not difficult at all = 0; minimally difficult = 1; somewhat difficult = 2; fairly difficult = 3; very difficult = 4; unable to do = 5" (2001, p. 1169).

As the therapist you need to palpate the lumbar spine during the test and assess for an inability to control the neutral spine i.e. looking for the amount of movement, muscular activity and bracing mechanisms. During the test you can also look at the contribution of the hip to the overall movement (by palpating the femoral head). As mentioned above the test is scored from 0-5, but the next step to determining if one side is heavier than the other, is whether the test can be augmented/modulated to get a different result?

Modulating the ASLR test

There are a variety of modulations which can be performed and the type of modulation depends on what you are trying to bias (hip control, pelvic form closure, lumbar spine stability, muscle control etc.) Below are a few ways in which you can modulate the ASLR test.

Hold onto feet to assess biceps femoris.
Add compression - over the lumbar spine, anterior abdominal wall, pelvic ring or hip joints
Increase muscle activation - contralateral shoulder (to engage the ipsilateral abdominal wall), PF, TrA, or multifidus.
Or you can add a neural bias (cervical flexion), change the posture of the thoracic spine or add a taping/belt bias.
The hip is biased by adding a PA accessory glide or change the degree of hip ER.
Trial of myofascial release and then reassess (particularly of the post hip capsule or iliacus anteriorly).
Disengage muscles by applying direct pressure to them and the observe changes to the movement. An example of this might be to palpate psoas through the abdomen.

Some of the more common modulations which I use are shown below.

Adding muscle activation. This image shows pushing up through the contralateral shoulder to bias the ipsilateral internal oblique and contralateral external oblique.

The hip is biased by adding a PA accessory glide

Adding compression over the lumbar spine. You can also add compression to the anterior abdominal way by squeezing their abdominals transversely.

Adding compression to the posterior pelvic ring. To compress the hip joints use the same handling but place your hands over the greater trochanters.

A normal response:

Greater abdominal and chest wall activation ipsilateral to the ASLR.
There should not be a change in breathing patterns or IAP (intra-abdominal pressure).
There should be minimal alteration to the position of the pelvic floor (this can be visualised with real-time ultrasound).

In a study conducted by Hu et al (2012), sixteen healthy nulliparous females performed the ASLR in three different environments; normal, with an ankle weight, and with a belt, and the muscle activity of the abductor muscles, rectus femoris (ispilateral) and biceps femoris (contralateral) were observed. The results indicated that:

All muscle activity was more with the ankle weight.
Abdominal activity was lower with the pelvic belt.
Under both conditions TrA and internal oblique were more asymmetrically active than external oblique; the abductor muscles engage in multitasking, combing symmetric and asymmetric task components.

In 2011 Hu and colleagues investigate the role of psoas in hip flexion using the ASLR test. Hip flexion will cause a forward pull on the innominate, which was previously thought to be counteracted by the contralateral bicep femoris and ipsilateral lateral abdominals, to press the innominate towards the sacrum for increased force closure. Their results indicated that:

Problems with the ASLR may reflect problems with force closure.
Abdominal wall activity counterbalances forward rotation of the innominate.
Contralateral BF activity causes transverse plane rotation of the pelvis, often visualised clinically as an upward movement of the contralateral ASIS. Such movement is counteracted by the ipsilateral TrA and IO.
Psoas is active bilaterally - most likely reflecting its activity as a stabilising muscle of the lumbar spine.
Iliacus, rectus femoris and adductor longus are active ipsilaterally to perform hip flexion on the moving side.

An abnormal response:

In a study conducted by O'Sullivan et al (2002) patients with chronic PGP were assessed and their movement patterns (minute ventilation, diaphragmatic excursion and pelvic floor muscle activation) were observed:

There was increased muscle activation bilaterally through the abdominal wall.
In asymptomatics there was no pelvic floor descent, no loss of diaphragmatic excursion but some variation in minute ventilation (increased, decreased, or unchanged).
On the symptomatic side there was increased intra-abdominal pressure and pelvic floor depression, diaphragmatic splinting and increased minute ventilation.
This demonstrated that people adopt bracing strategies during a low load task.
They also observed the effect of these bracing strategies with manual pelvic compression and found that the adverse bracing strategies were reversed.

Psychometric properties:

Mens et al (2001) investigate the clinical reliability and validity of the the ASLR test in patients with persistent pelvic girdle pain related to pregnancy. They performed a cross-sectional analysis of the ASLR compared to the posterior thigh thrust (a pelvic pain provocation test) and found the sensitivity to be 0.87 and specificity to be 0.94. Clinically in Melbourne we don't promote the ASLR as a pain provocation test, rather a loading test which is used in combination with the provocation tests to detect SIJ-related pain/symptoms. This is often referred to as Laslett's SIJ tests (Laslett, Aprill, McDonald & Young, 2005). This study does show that it's a reliable and valid test for clinical practice.

Roussell et al (2007) investigate the psychometric properties of the ASLR test in patients with non-specific low back pain. They performed a cross-sectional study to understand the internal validity of the ASLR test and Trendelenburg test. Their results indicated the internal consistency of these two tests is high i.e. that both tests assess the load transfer capacity of the pelvis. The authors did conclude that further research is required to understand the reliability/validity of these tests in a low back pain patient population.

Clinical use:

I use the ALSR as part of the special tests for SIJ but it is not limited to this assessment. There is so much more information that can be gained about the loading strategies patients adopt. Since understanding the normal and abnormal responses of this test and ways of modulation, I use the test as a loading test for the hip, pelvis and lumbar spine. If the correct modulation is found it can lead to quick changes in the patient's loading and this is transferrable into a home exercise program focussing on that particular element.

Identifying the psychometric properties of the ASLR test among different patient populations still requires further research but this shouldn't stop clinicians from using it as part of the motor control component of the physical examination. As for many clinical tests we have available, this one provides us with valuable information about load transfer and the ability to augment load transfer, but should be considered with other physical asterisk signs to determine the overall treatment path for the patient.

Sian

References

Hu, H., Meijer, O. G., van Dieën, J. H., Hodges, P. W., Bruijn, S. M., Strijers, R. L., ... & Xia, C. (2011). Is the psoas a hip flexor in the active straight leg raise?. European Spine Journal, 20(5), 759-765.

Hu, H., Meijer, O. G., Hodges, P. W., Bruijn, S. M., Strijers, R. L., Nanayakkara, P. W., ... & van Dieën, J. H. (2012). Understanding the Active Straight Leg Raise (ASLR): An electromyographic study in healthy subjects.Manual therapy, 17(6), 531-537.

Laslett, M., Aprill, C. N., McDonald, B., & Young, S. B. (2005). Diagnosis of sacroiliac joint pain: validity of individual provocation tests and composites of tests. Manual therapy, 10(3), 207-218.

Mens, J. M., Vleeming, A., Snijders, C. J., Koes, B. W., & Stam, H. J. (2001). Reliability and validity of the active straight leg raise test in posterior pelvic pain since pregnancy. Spine, 26(10), 1167-1171.

Mens, J. M., Vleeming, A., Snijders, C. J., Koes, B. W., & Stam, H. J. (2002). Validity of the active straight leg raise test for measuring disease severity in patients with posterior pelvic pain after pregnancy. Spine, 27(2), 196-200.

O’Sullivan, P. B., Beales, D. J., Beetham, J. A., Cripps, J., Graf, F., Lin, I. B., ... & Avery, A. (2002). Altered motor control strategies in subjects with sacroiliac joint pain during the active straight-leg-raise test. Spine, 27(1), E1-E8.

Roussel, N. A., Nijs, J., Truijen, S., Smeuninx, L., & Stassijns, G. (2007). Low back pain: clinimetric properties of the Trendelenburg test, active straight leg raise test, and breathing pattern during active straight leg raising. Journal of manipulative and physiological therapeutics, 30(4), 270-278.