Leg Length Discrepancy (LLD) means having one leg longer than the other. And that can cause back pain.
But often the legs are actually the same length, they’re just ‘acting’ different.
It can happen for different reasons, but it can lead to a host of secondary problems throughout the body.
So let me explain what it is, the two different types and causes, and what you can do about it.
Leg Length Discrepancy can cause:
- Back pain
- Disc bulges/herniations
- Hip and knee pain
- Neck and shoulder pain
- Headaches and jaw problems
- and can lead to osteoarthritis.
How to tell if you may have a LLD
- Do you tend to stand more on one leg?
- Stand in front of a mirror and notice if one hip looks higher, or one arm hangs further away from your body
- See if your trouser hems are more worn on one side
- Lie on the ground and ask someone to check if your legs look the same length
Why is LLD a problem?
Simply put, it puts the wrong kind of stress and pressure on different joints in your body.
If one wheel on your car is not balanced (perhaps you clipped a curb a while back) then that tyre will wear out faster than the others. Because the force going through it is different from what it’s made for.
The same thing happens in your body.
If you put the ‘wrong’ kind of stress on an area of cartilage, muscle, tendon, bone or ligament, then it’s going to be overloaded after a while. And that can lead to pain, inflammation, and eventually physical tissue changes, like osteoarthritis. For example, I’ve noticed on x-rays that the longer leg usually (but not always) is the side that gets arthritis in the hip joint and lumbar spine.
But well before any permanent changes, you can experience back pain just because your back muscles have to work harder on line side than the other, or because the spinal joints are getting more compressed on one side.
And as I mentioned before, the effects can manifest all over the body, in the hip or knee, neck or shoulder, or as something unexpected like headaches or jaw pain
But isn’t it normal to have one leg longer than the other?
I’ve never liked the term “Normal leg length discrepancy”.
Just because something’s fairly common (like divorce or depression, for example) that doesn’t make it ‘normal’.
When I was studying, the textbook notion was that any leg length difference less than 10mm didn’t matter. And I’ve even heard that repeated by some doctors, chiropractors and surgeons.
But I discovered that it’s just not true.
People have different tolerances
I’ve seen people walk into my office with such a big leg length difference that they’re tipping over to one side, but they never even noticed.
Even when you put them in front of a mirror and it’s very obvious.
Other people feel really out of sorts if their body isn’t perfectly balanced. Some people are just more sensitive to these things than others.
But even more peculiar, is that the wear and tear caused by it can vary a lot too. Just like some smokers live to be 100, some people seem to get away with having an unbalanced skeleton.
But not the majority.
Structural vs Functional LLD
It’s important to correctly diagnose whether a LLD is structural or functional (or both), because that changes how you treat it.
Structural LLD means one leg is physically longer than the other (or the pelvis is not symmetrical, like a tilted sacral base for example).
The main causes of structural LLD are:
- Genetics (it often runs in families)
- Trauma, like a fractured leg as a child that affected it’s growth
- Differences in the hip joints (like anteversion or retroversion of the hip)
- Diseases like polio or hip dysplasia
- Possibly developmental, where restrictions in the upper neck for example might affect how the body grows
Genetics is the most common, it’s just the way you’re made. But I suspect that developmental asymmetries happen more often than we realise.
Functional LLD means the legs are in fact the same length, but something’s making it look like one is longer.
Common causes of functional LLD include:
- Tighter hip flexors (iliacus & psoas muscles) on one side
- Restricitons in the upper neck causing a slight twist further down the body
- Weak gluteal muscles on one side, which again can be caused by restrictions elsewhere
- One foot being flatter (pronating) than the other
- A rotation of one of the low back vertebrae, causing a tilt in the lumbar spine (low back)
I always try doing a hip flexor release when I see a patient with a LLD, and most of the time it’s enough to straighten them up, which shows how common it is.
How do you diagnose LLD?
It’s important to assess and diagnose it properly, because if you get it wrong you can cause more problems. You can’t just assume that because one leg looks longer than the other, that it actually is (even after 15 years of clinical practice I still get surprised sometimes).
X-ray analysis is the most accurate way, but there may not be justification to take x-rays, and not every clinic has x-ray facilities available. In the UK, chiropractors are the only complementary practitioners who are qualified to take and read x-rays.
Based on my education and experience, this is the best way to assess for LLD:
- Don’t assume it’s structural or functional until you’ve tested it (and don’t just stick something in the patient’s shoe until you’ve cleared all the functional possibilities first).
- Try functional treatment first (hip flexor release, manipulation, mobilization, adjustments, etc.) for 1-2 sessions.
- If there’s no change at all, or very little (and it’s clinically justified) then do an x-ray analysis in a standing position.
How to treat Leg Length Discrepancy
Firstly, how you treat it depends whether it’s sturtural or functional.
Structural LLD, where one leg is actually longer, is pretty simple. Just put a heel lift (usually a bit of cork) in the shoe, on the short side.
It can often slip under the insole, so it doesn’t fall out and you never know it’s there. It’s important to get the height correct though (which is where x-ray analysis has the advantage), but if in doubt always start small and work up.
Personally, I have a structural LLD where my left leg is 9mm shorter, so I have a 9mm heel lift in my left shoe. I have one in every pair of shoes I own, including my slippers, and have even glued one to my flip flops for when I go on holiday (my wife has almost got over it). If I don’t wear one for any length of time, then my back begins to ache, my right knee clicks, and I generally feel uncoordinated and uncomfortable.
You can get heel lifts very cheaply, but my advice to you is this:
If you think you need a heel lift, get a proper assessment by a chiropractor/physio/osteopath first.
Functional LLD needs a different approach. Then it’s down to the skill of the practitioner to find out what’s causing the LLD and correct it appropriately.
The first thing I always go for is the hip flexors. Becuase 90% of the time the longer leg has tight hip flexors (I know, you’d think it would be the other way around, but that’s the body for you), and releasing those usually straightens things up. Then I look for restrictions in the spine, hips and pelvis.
Obviously all practitioners have their own particular techniques and systems though, and the most important thing is that it works for you. So if you think you may have a LLD, I recommend (firstly, do not just put a heel raise in your shoe) that you just find someone you get along with, who gets you results.
It might be your handbag!
Functional LLD caused by tight muscles on one side, is often the result of carrying something on one side all the time. Like a handbag, a laptop bag or kit bag, or carrying children on one hip. So you may have to modify the way you do certain things, which I know isn’t easy.
But if it’s causing you pain then it’s worth making the effort.
Functional LLD can happen any time
I have patients who come in for their monthly checkups and have a LLD one month, then not for a long time. It can be a transient thing.
But often the reason for that is something they’re doing day to day (as mentioned, like carrying bags or children on the same side all the time), so it’s likely to keep coming back until they change that habit.
Leg length discrepancy is common, and a common cause of back pain.
Whether structural or function it’s often easily corrected, providing it’s diagnosed correctly. So if you suspect you may have an LLD that’s causing you back pain, go get it checked out by a chiropractor, osteopath or physio.
It could make a huge difference to how you feel.