True leg length discrepancies are rare in my experience. Or, if it’s there, it’s so minor it’s not worth worrying about.
It’s such a simple, quick test, it’s worth doing sometimes though.
When to do this test
Typically a new person will tell me they have one leg longer than the other, or I’ll decide to assess them based on how they move. Maybe they seem to always be leaning to a side when walking, or whenever they squat / sit down they lean one direction. Whatever it may be.
First, you eyeball things with the person in standing. I’ll tell them to “Put your feet together, put each of your index fingers on that pointy part of your hip bone. Like where you would get a hip pointer.”
Then I’ll have them take their shoes off and do the same thing. This allows you to see if there’s any differences between shoes on or off, which could indicate how much they stand on one leg or wear down one shoe.
The big thing to understand at this point is we haven’t truly assessed leg length yet. Because the person is in standing, there could be a host of other factors pulling on those hips, all giving the illusion of a leg discrepancy.
Therefore, at this point some therapists will widen the legs. By doing this you’re assuring each leg is at a certain distance, which should reduce any muscular factors and give you a better indication of what’s going on structurally. So, sometimes you’ll see a discrepancy with the feet together but not with the feet widened, which indicates there is something going on muscularly and not a true leg length issue.
I don’t like this too much though. I feel like there’s still too much room for error, and honestly sometimes people really don’t get how to align their fingers right to begin with. As best I can, I like to get the assessment (and in general, assessmentS) out of the person’s hand and into mine.
So I put the person on the ground, keep their feet on the floor, but bend their knees up. By taking gravity out of the equation we can really hone in on what’s going on structurally rather than muscularly.
Make sure the person’s feet are even with one another. Don’t let one foot be in front of the other.
From here I’ll put a clipboard on their knees. If the clipboard is straight, there’s no leg length issue. If it’s tilted, there is.
You can then get more nuanced by assessing where the discrepancy is coming from, the tibia or the femur? You do this by looking at the legs from the side. We know one knee is higher than the other, but is the knee being pushed forward or backwards? Forward = femur discrepancy; backward = tibia. You may see something akin to:
I never go this far though. I only go as far as “Is there a true difference?” I’m not sure there’s any change to make in practical recommendations once it’s been discerned there is a difference i.e. it doesn’t matter where the difference is coming from; it only matters if it’s there.