The Long And Short of Leg Length Differences

I must see a social media post or some other discussion about leg length differences at least once a day. And I hear healthcare professionals saying how it’s a common cause of both pain and pathology, blamming it for a host of movement dysfunctions and muscle imbalances.

Well, I question this and the relevance of leg length differences as a common cause of pain or disability a lot. I also question how leg length differences are assessed and treated and if they need to be at all.

What Is A Leg Length Difference?

There are two main classifications of leg length difference, or as its technically called ‘Anisomelia’. One is called functional or ‘apparent‘ leg length difference, the other is called anatomical or ‘true‘ leg length difference.

Anatomical leg-length discrepancies are where there are differences in the shape of the pelvic, leg, ankle, or foot bones due to congenital deformities, disease, trauma, or surgery. These bony differences are further divided into two categories; those that shorten a limb, and those that lengthen it. 

Congenital growth deficiencies, bone or joint infections, growth plate fractures, and other traumas can cause lower limb shortening. Causes of lower limb lengthening are much much rarer and often caused by genetic conditions such as hemihypertrophy.

Apparent leg length discrepancies are when there are no significant structural differences of the bones but other conditions such as spinal scoliosis or other asymmetries create one leg to be longer or shorter than the other. Apparent leg length discrepancies are believed to be caused by things such as muscle weaknesses or imbalances causing things like pelvic torsion, foot pronation, knee varus or valgus.

How Do You Identify Leg Length Differences?

There are many methods to assess leg length differences, some more reliable than others. The gold standard is using radiographic imaging, with techniques called orthoroentogenograms, which is not easy to say but a guaranteed scrabble winner! These are a series of X-rays taken in succession of the hip, knee and ankle. Other imaging techniques such as CTs and MRIs are also found to be useful (source).

However, these methods are not infallible but more importantly they at not available to most therapists in day to day clinics. They can also be expensive and of course, have radiation doses to consider. So most leg length differences are assessed by therapists in other ways.

A common clinical test used is the supine bridge test or the Weber-Barstow Manoeuvre. This where the patient is asked to lie supine and perform a bridging movement with their legs together and knees bent at 90 degrees. An ‘eyeball’ check of the height of the top of the knees is then taken to see if there is any difference in pelvis (A) and the femurs (B) length by looking down from above, and then the tibias (C) by looking from the front.

However, this test doesn’t do well in its clinical reliability with a recent study finding the levels of inter-rater agreement reaching only moderate levels. A more reliable method is by measuring the distance between the bony landmarks of the pelvis and ankle with a tape measure. However, this still has issues with the location of these landmarks being challenging to find in some subjects, and leg muscle girth differences sometimes affecting the measurements.

An alternative method of measuring from the umbilicus or even the xiphisternum have been suggested and some suggest that the measurement is taken to the bottom of the heel so that any discrepancy in the ankle joint is also included.

Woodfield et al (2011) found assessors had moderate reliability with this method within 1/8th of an inch (that’s 3.2mm to us metric users) but excellent reliability within 3/8ths of an inch (or roughly 1cm). Jamaluddin et al (2011) also found tape measurements were accurate to within around 5mm when compared against radiographic images as does a more recent by Neelly et al (2013).

Other clinical tests used to check for leg length differences are checking the heights and angles between the pelvic bony landmarks of the ASIS and PSIS. Recently Digital Pelvic Inclinometers have been claimed to increase the accuracy and reliability of these tests (ref). However, on closer inspection we can see that this isn’t the case, with assessors often finding large differences of up to 10° even when measuring the same subjects on different days. And that’s before we mention the extremely high risk of bias and huge conflicts of interest this study has.

The relevant and useful information you get from all these tests are highly questionable, and as I’ve discussed before in my other posts about the SIJ the natural variation in skeletal morphology makes any test that uses bony landmarks pretty much invalid and useless.

Are Leg Length Differences an Issue?

Leg length differences are common, very common, very, very common. In fact, up to 95% of us are thought to have it (source) with the average being around 5mm with the right leg being most commonly shorter than the left (source). However, the more important question is do these leg length differences cause pain or pathology and if they do how can we tell?

When a leg length difference becomes an issue just isn’t clear at all, but it seems a general consensus in most literature and most clinicians is that anything over 1cm difference is probably worth considering (source). However, the keyword here is ‘consider’ and not panic or jump to hasty conclusions.

When ever someone has any pain or any pathology we have to take into account the many other factors that can contribute to them and not start blaming single sole factors such as leg length differences! We also need to recognise the remarkable ability of the human body to adapt and compensate for all kinds of asymmetries such as a leg length difference.

Many clinicians will blame a leg length difference for creating pain and pathology due to it increasing ground reaction forces in the shorter limb (source) which is thought to adversely over load, stress and strain joints, muscles and ligaments of the leg, pelvis, and lumbar spine. In fact, some even blame leg length differences for dental issues and TMJ issues, which I think is pushing the boundaries of plausibility too far.

Other studies have shown correlations with leg length differences and pathologies in the longer limb such as stress fractures and plantar fasciitis. Either way, there are many papers that blame leg length differences for many pathologies

For example, this large prospective trial on 3000 patients showed those with a leg length difference of more than 1cm have a greater prevalence of knee joint osteoarthritis more often in their longer limb. But, there are also papers that show no correlation between leg length differences and pathologies such as this on lateral hip pain and this on spinal scoliosis.

As always its important to remember that a correlation does NOT imply causation, and as with most things, I’m sure if we look hard enough and tortured the data long enough we could find that leg length difference is correlated with male pattern balding, bad driving, and a dislike of the colour purple .

Too Quickly And Easily Blamed?

In my opinion, leg length differences are a nice, easy, and convenient scapegoat for many clinicians to blame as a cause or source of their patient’s pain. This is because it’s often far easier to focus on these simple biomechanical suspects than look for the far more messy, complex, and difficult factors that can be contributing to their pain and pathology.

Also, it’s far easier to think that humans need to be symmetrical and perfectly aligned like some robot than recognise that humans are complex, messy, wonky, wobbly asymmetrical bags of bones, viscera, and soft tissues that have a remarkable and amazing capacity to adapt and tolerate things.

This ability for us humans to adapt to asymmetries is beautifully demonstrated in this neat little study in which they created leg length differences of up to 3cm in subjects with the use of built up shoes and measured their joint kinematics and forces when walking and found no significant differences as the subjects self-organised around their new biomechanical alteration.

However, large and sudden changes in leg length difference may be an issue for some and may need some management. For example, I see some patients after hip replacements with a sudden significant leg length difference after the operation that has caused some patients to experience new episodes of back and other pains. However, this could also be due to the fact that they are also now more mobile and active after the operation and have increased their activity levels significantly.

Treating Leg Length Differences

Many clinicians also treat leg length differences with many dubious things. Things such as ridiculous manual therapy techniques believed to reset pelvic misalignments, reduce overactive muscles, or release tight fascia causing fictitious postural imbalances and other pseudo-scientific claptrap.

Many do this I think because they feel that they have to justify their existence and fees and in an effort to demonstrate how skilled and knowledgeable they are. This gives them an appearance of expertise and competence to their patients which perversely helps them feel better with the silly treatments they get.

My advice is if you do suspect a leg length difference is a factor in your pain or issues then just try a simple inexpensive heel raise or insole in your shoes for a short while to see if it helps. If it does great use it to help calm down and reduce your issues. But once settled slowly see if you can wean yourself off it and see if your body can adapt slowly around your leg length difference, because you dont want to or may not be able to always wear a heel lift or insole!

Summary

  • Leg length differences are common, very common
  • Assessing leg length differences clinically is tricky and unreliable
  • Determining if a leg length difference is a factor or not in pain or pathology is even trickier and more unreliable!
  • Many leg length differences are NOT a significant factor and even less need correcting.
  • We all have an amazing ability to adapt and tolerate asymmetry, and in most cases already have.


As always thanks for reading

Adam

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  1. I’m really glad I have found this information. Nowadays bloggers publish just about gossips and web and this is actually irritating. A good web site with exciting content about physio, that’s what I need. Thank you for keeping this web-site, I’ll be visiting it.

  2. I would agree that the accurate assessment of leg length is extremely difficult particularly in the clinical environment. Even the gold standard of a CT scanogram has a degree of subjectivity as to whom and where the measurement markers are placed. I have measured some of these myself and usually take a group of measures to try and get a consensus. The varying clinical assessments are all prone to error and each practitioner should develop a consistent assessment technique but not rely on one measure for diagnosis.
    The degree of discrepancy relevant to injury is often quoted fairly high in the literature for exactly this reason; it is difficult to be precise with the assessment but, if you measure 1cm for instance it is likely to be present.
    However, the actual relevance is much more dependent upon a range of factors, not least how well the individual has adapted to the imbalance and their activity levels etc. as you state. I would entirely agree that an alteration to training could spark the problem but, by the same token, there can be a threshold of activity (a set distance for instance) beyond which the degree of discrepancy causes enough dysfunction to lead to injury. I would also proffer that this threshold reduces with age (eventually) which is why a problem may only manifest in later years.
    I assess LLD in a high percentage of my patients (accepting that this is a clinical assessment and will have error) and would estimate that less than 50% of these have any discernible LLD. Not scientific I accept but certainly not as high as 95% and I treat a pathological sample group.
    I would agree that LLD can be a scapegoat but it has to be considered as part of the overall diagnosis and management plan either for the short or long term. The secret of any functional / biomechanical assessment is to determine how much of the pathology is due to alignment (foot / leg / pelvis etc.), muscle strength / flexibility, neuromotor control / training patterns etc. If someone has had a one off issue and it is linked to control and training, that is clearly the target. However, if someone is having repeated asymmetrical injury patterns, LLD may be more relevant. If it is felt that the foot function is contributing to injury, then LLD has to be considered as altering foot function will alter the way the body adapts for the LLD.
    Our approach to assessing all of our cases is to determine what we feel are the key factors inhibiting / altering function and then to target these / refer accordingly. As podiatrists that means do we feel it is structurally related and requires control, due to neuromuscular control or training patterns with appropriate referral or a combination. We can then determine if any control needs to be for the short term or long term.
    In order to assess the clinical effect of LLD, we perform inshoe pressure analysis to look at symmetry. Rather than looking at absolute pressures / integrals etc., we evaluate symmetry of heel loading / force time curves and centre of pressure lines and then revaluate with LLD control.
    I have posted some examples on my Facebook page (https://www.facebook.com/PremierPodiatryLimited)which show:
    • A professional athlete with LLD but sufficient strength and control to function without any detrimental effect.
    • Someone walking who has asymmetrical force / time curves without but symmetry with control
    • Someone running who has symmetrical Centre of pressure lines without and symmetry with LLD control.
    I fully accept that much more research is required in this field but at the moment, this at least allows us to have an idea of the effect of discrepancy and control.
    With the introduction of our 3d gait analysis system, we have just started looking at the effects on more general function but it is too soon to comment but exciting.
    I agree entirely that orthoses are not required to control for LLD alone. In the majority of instance I will either provide a heel raise, a whole shoe insole (both of these are peanuts and I include as part of the consultation fee) or advise a shoe modification. If we wish to control foot function, then we will provide orthoses but also the appropriate level of LLD control.
    So, in summary, I agree that the assessment is fraught with error (a point I advise my patients) but personally give it more relevance than yourself. I do not get hung up on the degree of discrepancy, more the effect on the individual within the framework of their presenting history and the likely benefit of control whether the control I is simply for the LLD or as part of controlling foot function in general. Here we are in agreement; spotting the discrepancy is one thing, determining the relevance is another.

    • Hi Trevor
      First and foremost can I say thank you for your time and very valuable and valid comments.
      I agree with nearly all that you say here and I know that it comes across as I’m bashing LLD and insoles etc,and I am a bit as I do get exasperated with many therapists focusing on this and not the bigger issues. As I say I do accept LLD has a role in pathology and pains, but I still argue that give time and correct loading the body can and does adapt without the need of corrective devises, the issue is many patients dont want to or cannot afford to give the body the time it needs or they simply cannot be bothered to do the hard work!
      Anyway once again thanks for your valued opinion
      Kind regards
      Adam

    • Hi but what if you broke your leg and now have a leg 6mm shorter and no constant back pain. Will it get worse as get older or will your body adapt

  3. Thanks Adam, that was a great review of LLD and measurement. Certainly nothing there that hasn’t been said before, but it certainly something that needs saying!

  4. I found that article a very interesting read. Thank you for taking the time to write it and I look forward to more posts in the future.

  5. Thanks for a great article. I like how you don’t oversell yourself. I find the most useless people are the ones who won’t listen, think too much of themselves, and think they know everything. Anyway. I’m pretty sure I have this LLD. I’ve had it probably most of my life, as far as I can remember. I’ve seen some of “the best doctors in the world”, none of which picked it up, but the more study I do, the more I realize its whats been bothering my hips, hams, groins, and sijoint. I still don’t have the scans to prove the problem. I was hoping you could shed some more light on the types of scans available, and if they can be found in Canada, because I’ve had over 50 appts and the best I can get is a standing xray of my pelvis.

  6. Hi Adam,
    I have to agree with your point that LLD is not always the main problem when a patient presents with pain, however I have to disagree with your being ok with the way the body adapts to these leg length differences. As a physiotherapist and someone who has a functional LLD >1cm I have enjoyed studying the correlation to my own PFJ,SIJ and neck pain related to the imbalances that result from my own LLD. My right sided foot overpronation and internal rotation of my tibia/femur and anterior tilt has lead to my reoccurring PFJ pain. I can manage it with ITB rolling but this isn’t addressing one of the main contributors I feel which is my leg length difference. Leg length differences I believe can be one of the main driving forces for chronic pain.
    Regarding your statement that ” blaming LLD for a lot of patients pain presentations and issues just doesn’t make any rationale sense to me” I believe being a responsible therapist particularly with patients with reoccurring injuries/ patterns of pain or chronic pain In relation to my patients I feel it’s in my patient’s interest to address not just the local issue but to bringing attention to the imbalances stemming from foot/ankle and hip. I believe in LLD and those that are active the imbalances and the ‘adaptions’ higher up that are evident with LLD contribute significantly to reoccurring pain. Rather than call it “intuition”, I call it logic. Force not distributed evenly has the ability to cause excessive wear and tear and therefore pain etc. In the case of PFJ pain The TFL is more overactive on my shorter side, where I pronate and have more anterior tilt. Therefore the more I run this LLD is going to be causing my ITB to be tighter on my right side and my patellar to maltrack. Yes I address the localised issue of ITB tension, encourage VMO activation and use Mcconnell taping to reduce symptoms… but this is a short term solution. The shorter leg I believe is important to address the pronating foot with potential orthotics and to address the inhibition of gluteal muscles that could additionally have induced the pronation. Without looking at these main drivers it’s just going to lead to frequent relapse of the condition. Addressing this is also having the goal of reducing the continual overload on joints that over time would more likely lead to patellarfemoral pain becoming chondromalacia, tendonitis becoming tendinosis, disc pain becoming a disc bulge.
    I feel that your opinion on therapists who educate and bring LLD to the patient’s attention and insist on improving this to improve the patients condition are using LLD as a ‘scapegoat’ actually couldn’t be further from the truth. Therapists who treat the smoke and not the fire are more likely to guarantee returning business with the same reoccurring problems. It’s important to address the localised problem but physiotherapists are encouraged also to look at contributing factors? I know as a therapist if someone comes to me with chronic lower back pain and they have a leg length difference that is functional and an adaptive scoliosis, by treating the joints effected and looking at improving activation of inhibited muscles and stretching of muscles that are overactive +/- orthotics/heel raise will be ensuring my patient has long term less chance of future exacerbations but additionally less excessive force on joints in their spine and therefore a reduced rate of wear and tear.
    Lastly physiotherapists are the gurus of the musculoskeletal system and I think there is no problem in owning that in biomechanical assessment and management. It saddens me when patients report to me previous physiotherapists they’ve seen who have just used passive treatment like ultrasound or TENS only and provided some basic stretches without utilizing the skillset to investigate and address the biomechanical contributors and educating and tailoring a program specific to their patients.
    A good physiotherapist will look at the patient as a whole and address leg length discrepancy as best possible. It is not oversell, it’s justified good patient care in my opinion.

    • Hi Danielle
      There are so many points I wish to debate with you in your comment I don’t know where to start, and I really haven’t got time.
      I will just say that yes biomechanics are important to consider of course, but we are all guilty of over assessing and making rash and misdirected assumptions based on some sketchy evidence and peer opinion and beliefs that get handed down and ingrained.
      We must consider the body as a diverse and adaptable ecosystem not like a car or a machine, we are biological with a wonderful advanced and crazily complex neural system, regulating it all, this is what we should focus on more, not the leg difference of pelvic asymmetry which is mostly not relevant
      Regards
      Adam

  7. HI Adam,
    I broke my leg when I was 10 months old and now 35, after two children I am experiencing a lot of pain on my longer side. Foot ankle, achilles, calf, knee, thigh, hip and lower back. I believe my discrepancy is approx 3 cm due to my femur being differing lengths. Any advice… i’m looking into seeing orthopaedic surgeon and podiatrist for advice. I also am starting clinical pilates one to one helping me to gain strength but I am not understand how anything can help me given the level of discomfort I am in daily as soon as I start moving. I am hoping you can direct me as it’s tricky running after two little boys, and I’m an athletic person otherwise!
    Thanks
    Amy (UK)

  8. I’m confused why would a tape measure be used to measure leg length and not a more appropriate instrument such as an anthropometer/long sliding calipet, or a segmometer?

    • Because they are not easily accessible or simple to you as a tape measure, and as I have said the research shows it is fairly reliable as other measures! Fairly!

  9. Sorry. As someone with a true lld I disagree. You think it’s better for the body to adjust to lld rather than a heel lift. In my case – and I assume many others – I developed scoliosis as a result. So addressing this early enough with a heel lift would have prevented this.

    • Im sorry to say there is NO evidence that leg length differences cause or contribute significantly scoliosis, or that a heel wedge would have prevented one from developing.
      Many people with scoliosis have NO leg length differences and also think about the amount of time you are not standing or walking throughout your life, this time will out weigh time on your feet.

  10. have to agree with amplewor. left leg longer, pushes left hip out, causes pain in left hip, and eventual shifting of spine to S shape. Right shoulder below left. It’s common sense really. And your logic Adam is weak. Just because some scoliosis patients have no leg length difference is completely irrelevant. Smoking causes cancer, but there are lung cancer patients that don’t smoke.
    In my case, 1.5cm difference, I didn’t notice until early 30s. Insoles have saved me.

    • Why would a longer leg that you have had all your life now start to push your hip out? And insoles havent saved you, they have given you a belief that they have helped which you have accepted.
      Cheers
      Adam

  11. I am a physiotherapist working in a private practice in Melbourne. I often have patients spontaneously tell me (as part of their medical history along with major surgeries/injuries) that they have one leg longer than the other and that they were informed of this during previous consultation with a chiropractor, osteopath or physiotherapist.
    I can see that this usually stays firm in the mind of a patient as it conjures up dramatic images of deformity and can provide them with a “aha!” moment and a convenient hook to hang all of their physical problems on. It also has the effect of making the therapist seem like a genius to a patient because they are taking a “holistic” approach by investigating something that can, at surface level, seem like a deep underlying cause which has never been investigated before! This makes the therapist and the patient feel quite good during that consultation (which is probably why patients and therapists develop strong emotional attachment to this idea). It also sets up quite a convincing premise for a powerful placebo effect- your leg is short and this insert will make it the correct length again! Problem solved! Now you can stop worrying! (see also- your back is out of place, let me crack that back in for you).
    I am not saying that people wont see some improvement from this approach (we all know how powerful the placebo effect is) but given the available evidence, I doubt this improvement is coming from biomechanical factors. It also has the dangerous effect of reinforcing a body image of deformity and pathology in the patient that they will likely carry with them the rest of their lives (“ah my backs sore, must be my bloody short leg that’s causing it again!”). I feel that in the long term it would be much more beneficial to a patient to reinforce the idea that the body does not need to be mm perfect and that it is a self-modifying machine built to adapt.
    You can then fix a problem by addressing strength and range of motion issues, load management, weight loss, etc. while all the while promoting positive body image and independence. That would be the true holistic approach.
    Disclaimer- Obviously huge leg length discrepancies (getting up to 5cm) caused by trauma or congenital defects need to be addressed. This post is about the small ones in general population that are pathologized unnecessarily.

  12. You sound like your mind is all made up! Obviously, you don’t suffer from true LLD and have decided to portay those of us who do as some kind of freaks. Sorry I wasted my time reading your entire blog… Obviously, you don’t know what you’re talking about.

    • Hi Sylvia, I am not sure what makes you think or say that I portray those with LLD as freaks… thats just nonsense. If you read the blog you will have seen that I say LLD occur in many many people but they dont cause pain or disability in many many people.

  13. First of all most therapists don’t evaluate functional leg length discrepancies correctly. Looking at LL supine only tells you nothing. Have the patient move supine to sit will demonstrate an equal alignment or a functional discrepancy. The cause is an imbalance in the pelvic area. How they present will give you a good idea of what is usually causing it. Balance the muscles, correct the alignment and symptoms are typically resolved. If symptoms are not resolved, look for upslips, sacral torsions, etc. PLEASE DONT JUST LOOK AT SOMEONE SUPINE! Never use a lift in a shoe unless you know via X-ray that it is a true LL discrepancy. You will only cause more problems for this patient.