Orthopaedic use of this test concerns hip and gluteus medius function.
Gluteus medius (and its little brother, minimis) keep the pelvis and trunk level while lifting the opposite leg. Without these muscles, the pelvis would immediately collapse to the side of the lifting leg. Without them, efficient gait would be impossible.
This test can detect significant weakness in the abductors of the weight-bearing hip by looking to see if the pelvis drops towards the raised leg.
But as spinal function specialists we can also use the test to observe and think about the lumbar spine.
I use this test either just before or just after active movements.
Using the test to observe lumbar function, we are not so interested in how ‘wobbly’ the patient is.
That’s because it’s possible for a patient to be quite wobbly on either leg and yet, from a spinal point of view, balance well.
Many factors (neurological, fitness, problems with other areas in the lower extremities, and so on) affect stability.
A quick definition of this would be:
Good spinal balance is where the spine stays broadly in the centre-of-gravity midline during single-legged stance.
Symmetry – or lack of
Of particular interest is whether we see asymmetrical functioning in the lumbar spine.
A key concept is that when a patient lifts a knee – for example, to waist height – the lumbar spine should side-bend towards the raised leg.
Any failure of the lumbar spine to side-bend in this direction will thus affect the way the patient balances.
Of course, side-bending is the critical movement, along with extension, of this area of the spine.
We can observe this.
With the patient’s right knee at waist height, how well does the lumbar spine bend to the right, and with a mid-point of the lumbar curve at L3-4?
Focus on the grounded leg and the position of the trunk above it.
Clearly, in advanced hip disease, or in serious weakness of the gluteus medius (e.g. paralytic polio, or severe L4-5 motor affected radiculopathy), we would see the pelvis dropping towards the lifted leg, with all kinds of adaptations to this occurring further up.
However, in the vast majority of cases, we are interested in more subtle clues than this. A failure to bend to the right in the lumbar spine will variably produce the following signs;
- A hitch or adjustment in stance as the patient commences the right leg lift – a less natural initiation of balance with a hesitation.
- A lean to the left of the trunk, to reduce the effort required of the left hip abductors – a kind of ‘cheat’ compensation.
- If this slight lean to the left isn’t well-coordinated, the patient will wobble more as they hunt for the right compensation.
- A straight, not right side-bent, lumbar spine.
- In even more subtle cases, and where the patient is quite fit and coordinated, they might hide these signs. We need to look very carefully in these cases.
Testing both sides provides much information that we can use to predict likely findings in other active and passive exams.
Using this test, it is also possible to make predictions as to how the lower extremities will be affected by an asymmetrical pattern of balance caused by a side-bending failure in the lumbar area.
For example, if balance on the left leg is affected by lumbar dysfunction, and a sedentary patient takes up running, then we can infer that collateral strains will go through the left knee (the grounded leg) during the stance phase of running.
On the other limb, it is at heel strike that the right knee, and the hip/pelvis above, will have an abnormal jolt. In this situation, the right knee might develop anterior symptoms. For example, patella tracking issues.
Whether symptoms emerge depends, of course, on many other factors, and all of this analysis is just a rough heuristic, a guide – if you like – to making sense of complicated situations.