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:
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.