Is your one leg longer than the other? Maybe your doctor or therapist even told you that this is the cause of your pain? Well, based on the current scientific evidence, the chances of you having to do anything about your leg length discrepancy is 0,1 %. And in this article I’ll explain to you why.
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How Do You Even Know That You Have a Leg Length Discrepancy?
Your doctor or therapist probably looked at you while standing and checked if your pelvic crests are at the same height. Or you were lying on a bench, and they checked if one leg lies lower than the other.
There’s a study done by Gibbons et al., which analyzed, whether those tests can actually predict a leg length discrepancy.
They simulated a leg length discrepancy of 0,5 and 1 cm using insoles and tested whether therapists could detect the difference. The results were not much better than a coin toss.
And even a more objective assessment like using a tape measure doesn’t really perform that well, because it’s prone to errors due to things like:
- Bony anomalies
- Thickness of the thigh muscle
If you really want to know whether you have a leg length discrepancy or not, you should to get an imaging procedure like an X-ray or MRI. Otherwise, I’d question the statements of the therapists and doctors.
But let’s assume you have a leg length discrepancy. Is that common? When does it become problematic? Is a difference of 0,5 cm bad already? And how does that relate to pain? Let’s take a closer look at this.
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How bad is a leg length discrepancy?
It’s important to know that leg length discrepancies are extreeeemely common, as Knutson (2005) showed in his work.
Guess how often legs are actually the same length?
Only about 10% of the population has legs of equal length!
The other 90% have a leg length discrepancy of about 0,5 – 1 cm. And only about 1 in 1000 people has a leg length discrepancy of ≥ 2 cm.

Most studies have examined whether a leg length discrepancy is related to back pain. Sheha et al. reviewed over 47 studies and came to the following conclusion. I quote:
We conclude that the correlation between low back pain and LLD is weak at best. It is unclear at this time what degree of LLD is required to cause symptoms.
Lederman wrote a great scientific paper that eliminates many of the structural, biomechanical, and posture-oriented beliefs that still persist today.
In his study, he debunks many things that were previously thought to be related to back pain. The following figure shows a few examples:

Nowadays, we know better.
We know that the human body is enormously adaptable and can usually handle bony deviations or signs of wear really well (Lederman 2011).
Of course, it would be wrong to say that a leg length discrepancy can NEVER be related to pain.
So when does a leg length discrepancy matter?
Many studies suggest that a leg length discrepancy of ≥ 2 cm is necessary to be clinically significant, meaning it can have a relevant impact on pain and function (Knutson 2005).
Remember how I said that only about 1/1000 people have leg length discrepancy of ≥ 2cm?
So, the likelihood that this is you is about 0.1%.
Additionally, it’s important to note that this 2 cm value is not a hard limit. It depends on several factors, such as:
- Age
- Sleep
- Activity level
- How long you’ve had the leg length discrepancy for.
I want to focus particularly on the last point. As Lederman described in his study, humans are incredibly adaptable.
Especially when things happen relatively slowly or have always been there.
Disc herniations that develop slowly, scoliosis, or a leg length discrepancy from birth generally do not cause problems in most cases.
This is because the body has had enough time to adapt and adjust.
It’s a different story if the leg length discrepancy occurs more or less suddenly (e.g., after breaking your thigh-bone or a hip replacement) and is accompanied by pain and/or loss of function.
In such cases, it can indeed be the primary driver of the pain, and it’s certainly worth addressing it (e.g., through a shoe lift).
One Leg Longer Than the Other – Should You Wear Orthotics?
There are larger studies, such as the one by Campbell et al., which have looked more closely at the topic of orthotics. And they found that the evidence on orthotics is faaaar from conclusive.
However, since orthotics are relatively inexpensive and carry low risk, it can be worthwhile to try them out (especially if the leg length discrepancy has only recently occurred).
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Is a Functional Leg Length Discrepancy Bad?
If you’ve never heard of it: this means that anatomically your legs are actually the same length, but something else in the system is off.
Reasons like shortened muscles on one side, a pelvic tilt, or some other nonsense might be given.
I would be VERY cautious here because these explanations are not scientifically supported and are based on outdated thinking.
Again, I refer to Lederman, but there are many other studies as well.
In short: It’s highly likely that your leg length discrepancy was poorly diagnosed and falls within a clinically insignificant range.
If you want to find out why an anterior pelvic tilt is not the cause of back pain, then check out this article now.
Literature
- Campbell, T. M., Ghaedi, B. B., Tanjong Ghogomu, E., & Welch, V. (2018). Shoe Lifts for Leg Length Discrepancy in Adults With Common Painful Musculoskeletal Conditions: A Systematic Review of the Literature. Archives of physical medicine and rehabilitation, 99(5), 981–993.e2. https://doi.org/10.1016/j.apmr.2017.10.027
- Gibbons, P., Dumper, C., & Gosling, C. (2002). Inter-examiner and intra-examiner agreement for assessing simulated leg length inequality using palpation and observation during a standing assessment. Journal of Osteopathic Medicine, 5(2), 53-58.
- Knutson G. A. (2005). Anatomic and functional leg-length inequality: a review and recommendation for clinical decision-making. Part I, anatomic leg-length inequality: prevalence, magnitude, effects and clinical significance. Chiropractic & osteopathy, 13, 11. https://doi.org/10.1186/1746-1340-13-11
- Lederman E. (2011). The fall of the postural-structural-biomechanical model in manual and physical therapies: exemplified by lower back pain. Journal of bodywork and movement therapies, 15(2), 131–138. https://doi.org/10.1016/j.jbmt.2011.01.011
- Sheha, E. D., Steinhaus, M. E., Kim, H. J., Cunningham, M. E., Fragomen, A. T., & Rozbruch, S. R. (2018). Leg-Length Discrepancy, Functional Scoliosis, and Low Back Pain. JBJS reviews, 6(8), e6. https://doi.org/10.2106/JBJS.RVW.17.00148