Foot Pronation and Leg Length Differences

This is a disappointing article to write as I been going on about it for more than 15 yrs, have written about it before in several other places and so have a lot of other people, but the myth just won’t go away. The myth is that when there is a leg length difference, the foot (or more specifically the subtalar joint) will pronate more on the longer leg side to compensate for the difference in leg length (and by implication, allegedly increase the risk for overuse injury due to that overpronation).

The myth did not start with the good work of Bill Sanner, but this work was used to reinforce the myth. What Sanner et al showed was that pronation at the subtalar joint can shorten a limb by up to almost 1 centimeter. This implies that the body could pronate the foot more to even up the leg length difference. Foot pronation as a compensation for a leg length difference is widely taught in Podiatry schools, at podiatry meetings and in podiatry textbooks. It does not often seem to come up in orthopedic, physical therapy or chiropractic text books – I have long been intrigued and wonder why this is the case? (I have my theories on this, but will keep them to myself for now ☺)

I am not talking here about those who have asymmetrical foot pronation for other reasons. This can lead to a functional leg length difference. I am talking about a structural problem in one or more bones of the lower limb, so one limb is shorter than the other. The propaganda is that the foot will pronate more on the longer side to shorten the limb, which can make sense as Sanner’s work showed that this can occur for up to 1 cm. However, I never bought into that myth as my own clinical experience was that I used to see the foot on the shorter limb pronate more just as often as the longer limb. I used to have students come up to me and ask me why the patient they were assessing was pronating more on the shorter side when they were taught the opposite. They were confused and could not understand. I used to ask them why would it? What evidence is there for it? … there never was any!

Try this: Stand up; try and actively pronate one foot; note how much energy that requires. Now just stand with a slightly flexed knee; note how little energy that requires compared to actively pronating the foot. If you were the body and had a structural leg length difference, how would you want to compensate? Pronate the foot which requires energy or flex the knee more which require much less energy?

What does the evidence say? A number of studies have looked at this: Bloedel & Hauger who used digitized video during treadmill running of 12 subjects with a leg length difference and found no statistical differences between the short and long leg for the amounts of calcaneal inversion and eversion. They concluded that subtalar joint kinematics are not affected by leg length differences.  Other similar studies reported the same. We even did one and compared the calcaneal angle, navicular drift and navicular drop during static stance of a dozen people with a structural leg length difference and found no differences between the short and long leg:


How does the body compensate for a structural leg length difference? According to the Bloedel & Hauger study, they flex the knee more on the long side (see the ‘Try this’ above!).

I do have another issue with compensations for a leg length difference that I will get into another day, but in the meantime, ponder this: When you are running, only one leg is on the ground at a time. If there is a structural leg length difference, how does the body even know the leg is short if only one leg in on the ground?

As always, I go where the evidence takes me until convinced otherwise. and the evidence says that foot pronation is NOT a compensation for a structural leg length difference.

Bloedel PK, & Hauger B (1995). The effects of limb length discrepancy on subtalar joint kinematics during running. The Journal of orthopaedic and sports physical therapy, 22 (2), 60-4 PMID: 7581432

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7 Responses to Foot Pronation and Leg Length Differences

  1. Simon Spooner August 10, 2013 at 6:37 am #

    Craig, in answer to your final question here: “If there is a structural leg length difference, how does the body even know the leg is short if only one leg in on the ground?” If we model the running body as a spring mass system and assume our two legs are modelled as identical springs, but of differing lengths it is obvious that the sagittal plane displacement pattern of the centre of mass (CoM) will vary according to the length of the leg spring which is in contact with the ground. Thus, in a structural leg length discrepency with all other factors being equal, we should see variation in the amplitude of ocillation of the CoM as the support leg changes from the left to the right legs. Hence in compensation the body may modulate leg stiffness (making the longer leg more compliant and / or making the shorter leg stiffer) in order to maintain a more constant displacement pathway for the CoM as is seen when runners ambulate across surfaces of varying stiffness; to me it is the CoM displacement pathway which is the “preferred movement pattern” which Nigg alludes to.

  2. Claudio August 25, 2013 at 2:20 pm #

    Dear Craig,

    how about standing? In that situation, one could use both strategies: flex the knee and pronate the foot. How about jumping sports? Basketball, for example, the athlete jumps and when landing, may flex the knee and pronate the foot. Don’t you think in these situations more pronation would “help”?

    What do you think about a different test for “feeling” LLD? Stand barefoot, and put a sandal on one of the feet. That leg is longer, one will probably flex the knee and pronate also.



    • Craig Payne August 25, 2013 at 6:46 pm #

      The evidence says that people don’t pronate to compensate for a LLD.

  3. mo will April 15, 2015 at 1:51 pm #

    Perhaps my situation may help someone dealing with the compensation issue. I have a leg length discrepancy of 1 inch, resulting from a hip replacement and broken bones in the same leg. I used to run, now I cannot. I tried heel lifts, which didn’t help with running, because i run on my forefoot. I also tried getting a shoe length insert built onto my shoe(and another time within the shoe). These were too hard to run on, and felt like running on a block on my shorter side, thus i couldn’t build a stride.

    The success I have had was in finding one regular shoe with a large forefoot (such as a hoka one one) for the shorter leg and a shoe with a low forefoot (such as the nike free 3.0) for the longer leg. Although the shoes are different in traction, etc, the discrepancy in their sole thickness offsets my LLD. It looks funny for a guy running on a basketball court with two different shoes, but I am just happy that I can run now. Hopefully this may be helpful to someone in a similar situation- find out your LLD and look at different shoes with different forefoot thicknesses that seem to match your LLD. Then go to the stores and try them on. Good luck and God bless.

  4. Happy Trails July 12, 2016 at 10:30 am #

    I’m an endurance athlete, cycling, distance running etc.. I had a low speed fall from a bike on to my left PSIS and weeks after developed an antalgic posture, “sinking into my left hip” and posteriorly rotating my left innominate, creating a functionally shorter left leg. ! had an unremarkable pelvic xray and abdominal ultrasound but pain in my left groin area, left inguinal ligament area, and left lower back.

    My casual static posture changed, my knee on the contralateral leg bent to compensate. There was also a progression to some compensatory external rotation that followed the knee flexion, which then further progressed to increased pronation after a few more weeks. The surrounding muscles and fascia of my left hip (QL, rectus femorus, Sartorious, IT/TFL, Oblique, glute med, glute min) seemed to all get short, tight, and hold that innominate “hiked” and in a posterior rotation. This limited my internal and external femur rotation, but mostly internal and Hip extension was also limited. When I returned to running a couple weeks after the injury, the pain was lessening, but my gait was compensating for the pain. I remember cycling through different movement patterns. I was pretty foolish to think it would just get me through the healing process so I could continue to train, and that it wasn’t going to become a programmed faulty movement pattern over time.

    Within 3-6 weeks I remember most of my hip area pain being gone, and my training ramped up in an intense but periodized fashion, until about 12 weeks out I started having insidious tendinopathy on the right ankle (posterior tibialis tendon) over pronation and a “falling arch” that only continued to get worse regardless of activity modification and any treatment to that arch and ankle (I presented my PTT ankle/arch pain to multiple GP’s, Orthopedic Doc, Physical Therapists). UNTIL I realized I was being stupid and oblivious to having normalized this left antalgic hip posture, which was essentially twisting my pelvis and creating a functionally shorter left leg, and normalized the related faulty movement patterns. I finally holistically assessed myself beyond just my ankle… Later had a couple PT’s verify hip related issues and shed even more light.

    While a LLD alone may not cause overpronation in the longer leg as you stated, I believe what I am experiencing is the same root cause (posteriorly rotated left innominate) of my functionally shorter leg, is also causing my gait abnormality and resulting over pronation, arch collapse, and PTT tendonitis.

    My gait changed in a way that affected my backside mechanics, namely the drive off my trailing leg. With limited internal rotation, my forward propulsion isn’t 100% forward, I am getting thrown off to the right diagonally just slightly with each push-off from my left foot during hip extension. The right “longer” leg is having to dynamically catch and redirect this lateral inefficient diagonal energy during midstance (faulty movement patterns), repetitively stressing out these lateral stabilizers which also support and stabilize the arch and effectively regulate pronation, otherwise I would be running slights to the right and not straight ahead. (I’m talking micro amounts of abnormal posterior tib muscle/tendon recruitment to redirect and laterally stabilize magnified over 20 mile trail runs etc = RSI & trauma)

    I’ve learned a lot through this process, hindsight sure is 2020. I am currently undoing all of my postural and movement foolishness, but I would just like to highlight my case of concurrent development of a functionally shorter leg with over pronation in my functionally longer leg, and my personal assessment of what the heck is going on, in case it hopefully helps anyone else who may be dealing with something similar..
    -happy trails

  5. Frederick July 20, 2016 at 3:28 am #

    Hello Craig. I have a structural 0.6″ LLD and neither of my feet “over” or “under” pronate. The more equally and my shoes do not show uneven wear. I have read that the hips twist to “shorten” the longer leg, and this is what my body has done. The longer leg twists to the back and the shorter leg twists to the front. When deciding which direction to rotate my bike saddle, counterclockwise was the obvious choice as my left is my longer leg. From what I’ve read, the longer leg is more susceptible to injuries, and my only injury in 37 years of running (avg 50 mpw) is a sprained ankle that was actually a longitudinal split tear of the peroneus brevis tendon.

  6. Rolland Ansah August 7, 2016 at 3:32 pm #

    hi Craig
    I wrote my thesis on simulating LLD, whereby the compensation was not only happening on the foot, since one was podiatry student, however it was refreshing that the results indicated compensation within the spine and the knee. and the changes of CoG. I believe that’s the reason chiropractic can not fix them with manipulation and is patient send away to see the the podiatrist to deal with it. Thanks for your articles and when is your book coming out

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