Barefoot vs Shod and patellofemoral joint stresses

There is an increasing number of studies on patellofemoral pain syndrome or anterior knee pain in runners and the affects of gait changes on the biomechanics of it. The British Journal of Sports Medicine just published this:

Take your shoes off to reduce patellofemoral joint stress during running
Jason Bonacci, Bill Vicenzino, Wayne Spratford, Paul Collins
Br J Sports Med doi:10.1136/bjsports-2013-092160
Aim: Elevated patellofemoral joint stress is thought to contribute to the development and progression of patellofemoral pain syndrome. The purpose of this study was to determine if running barefoot decreases patellofemoral joint stress in comparison to shod running.

Methods: Lower extremity kinematics and ground reaction force data were collected from 22 trained runners during overground running while barefoot and in a neutral running shoe. The kinematic and kinetic data were used as input variables into a previously described mathematical model to determine patellofemoral joint stress. Knee flexion angle, net knee extension moment and the model outputs of contact area, patellofemoral joint reaction force and patellofemoral joint stress were plotted over the stance phase of the gait cycle and peak values compared using paired t tests and standardised mean differences calculated.

Results: Running barefoot decreased peak patellofemoral joint stress by 12% (p=0.000) in comparison to shod running. The reduction in patellofemoral joint stress was a result of reduced patellofemoral joint reaction forces (12%, p=0.000) while running barefoot.

Conclusions: Elevated patellofemoral joint stress during shod running might contribute to patellofemoral pain. Running barefoot decreases patellofemoral joint stress.

This study clearly showed that patellofemoral joint stress was lower when the runners were running barefoot compared to running in shoes and is consistent with another recent study that showed knee loads were reduced in forefoot strikers. The mechanism is probably due to the: “reduction in the PFJ reaction force occurred due to the smaller knee flexion angle during the stance phase of running, which decreases the demand on the quadriceps muscles“.

This has potential to assist in the management of patellofemoral pain syndrome, with the following caveats:

  • The participants in the study did not have patellofemoral pain syndrome and were healthy, so its not known if the same effect would happen in those with symptoms (though there is no reason to believe that they won’t).
  • This was an acute intervention and the participants were novices and not habituated to barefoot running; it is not known if the effects would be there if the runner was habituated to barefoot running. It could be that the novice barefoot runners run somewhat more tentatively and this may or may not have been reason for the reduction in load at the patellofemoral joint.
  • The authors did not report on what loads or forces increased in the participants. It is not possible to reduce the ‘load’ in one tissue without increasing it somewhere else. Presumably, as shown by Kulmala et al, the ankle ‘loads’ increased to allow the knee ‘loads’ to be decreased.

As always, I go where the evidence takes me until convinced otherwise, and this is pretty good evidence  that we need to be looking at gait changes in those with patellofemoral pain syndrome. Just how much this should be implemented into clinical practice in the absence of an actual clinical trial is still open to debate.

Jason Bonacci, Bill Vicenzino, Wayne Spratford, Paul Collins (2013). Take your shoes off to reduce patellofemoral joint stress during running British Journal of Sports Medicine DOI: 10.1136/bjsports-2013-092160

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9 Responses to Barefoot vs Shod and patellofemoral joint stresses

  1. Andy July 14, 2013 at 4:15 am #

    Study would have been more interesting if they added in a range of heel drops – ie standard running shoe – 12mm 8mm 4mm and zero drop as well as barefoot

    but still a good study

  2. Rodger Kram July 16, 2013 at 12:58 am #

    Study reports12% lower peak stress during each step. I think that most studies show a higher step frequency when barefoot. Does knee pain/damage result from less frequent bigger hits or more frequent smaller hits? I think the jury is still out on that one.

    • Craig Payne July 16, 2013 at 1:10 am #

      Thanks Rodger; I have been thinking about this since writing the above. The study was on barefoot vs shod and showed the 12% reduction; but was the reduction due to:
      a) The barefoot condition
      b) The forefoot striking (which is probably more likely in the barefoot condition)
      c) An increase in cadence (which is probably more likely in the barefoot condition and in forefoot striking)

      They did not collect any data on cadence (they did control for speed between conditions), but I assume it is probably safe to assume that there might have been an increased cadence in the barefoot condition, so your point is a good one: a 12% reduction per step, but taking more steps –> we need a clinical trial.

  3. Chris Delpierre July 16, 2013 at 8:34 am #

    Hi Craig

    Thanks for helping us ordinary mortals understand research!

    Has anyone worked out what the optimum knee flexion angle should be?



    • Craig Payne July 16, 2013 at 8:45 am #

      Chris; I don’t think so, but would assume an angle at the knee in the sagittal plane at foot contact of around 15-20 degrees would be accepted as probably a pretty reasonable angle.

  4. angie July 16, 2013 at 9:37 pm #

    Hi Craig

    I followed a link here from a barefoot forum in which they are claiming you are wrong with the comment about increasing the ankle loads. Can you expand on that?

    Runner Princess

    • Craig Payne July 17, 2013 at 2:32 am #

      Thanks Angie and thanks for emailing me back with the link!

      I never cease to be amazed at the strong clinical opinions held by those with no clinical training or clinical experience. I also never cease ot be amazed at the strong biomechanics opinions held by those with no biomechanics experience or biomechanics training!

      It is simple biomechanics: you can not decrease the load in one structure without increasing it in another (with one caveat of if you loose weight you can decrease it) – its not rocket science!

      Every study that has looked at this has shown it. The above study only looked at knee loads – they did not collect data on loads elsewhere let alone report on them. The study I mentioned above by Kulmala et al clearly showed that a decrease in knee loads led to an increase in ankle loads – I don’t get why some find that so hard to grasp. I do acknowledge that I could have used my terminology a bit better and “loads” may not be the best word.

      If you heel strike: impact loads are greater; loads at the knee are greater; and the tibialis anterior muscle works harder
      If you forefoot strike: forefoot dorsiflexion moments are greater; foot dorsiflexion moments are greater; ankle loads are greater; all muscles that have tendons that pass behind the ankle joint axis or under the midfoot joints works harder.

      It is six of one; half a dozen of the other. Different running forms load different tissues differently. Both have different injury risk profiles as they load different tissues.

      Most studies now show the global injury rate between minimalist vs shod and heel strike vs forefoot/midfoot are the same; so there is no global advantage of one over the other.

      The rhetoric and propaganda from the fan boi’s is responsible for hurting a lot of runners.

      As a clinician, I transition some runners to minimalism/forefoot striking as it is suitable to reduce the load on the tissue they have a problem with. I also transition some back to heel striking as forefoot/minimalism/barefoot was increasing the load in the problematic tissue. Others I leave alone as their ‘form’ has nothing to do with the injury. Fortunately, the fan boi’s that post in social media do not get to make clinical decisions.

      The above study was only a lab based study on normal runners. It was not a clinical trial on patellofemoral pain syndrome. It brings up the debate on when to change clinical practice based on ‘lab’ based studies vs clinical outcome studies. There are a number of lab based studies pointing to an increase in cadence may be a good thing for patellofemoral pain syndrome. In the absence of clinical trials what should we do? – go with all the propaganda and rhetoric from those with no clinical or biomechanical experience who post in social media or go with the balance of scientific evidence in context to make a reasoned clinical decision?

      Look at this way: if you had a serious medical condition and you and your physician had to make a decision what to do, what would you want to happen? Would you like to be treated with what the preponderance of scientific evidence says works? Or would you like to be treated with something that a lab based experiment in a petri dish on some normal rather than diseased cells suggested might help?….why should a running injury be treated any different?

      • Craig Payne July 17, 2013 at 2:33 am #

        Geeeez, I just realized how long that rant was

  5. Craig Payne July 23, 2013 at 9:00 am #

    Just for completeness, I responded to a question on the above research in another section here; so posting it below as well:

    Angie; thanks. This is the study you referring to.

    It is NOT evidence that barefoot is better. Yes, I have seen all the claims in the crankosphere blogosphere that it is, but I pretty sure almost all of those are from people who have not even read the full study, yet assume they can comment on it with some sort of ‘authority’.

    The authors in the paper (and in subsequent comments on Twitter) were very cautious to not make that conclusion.

    All the study showed was that in healthy runners without an injury, that the ‘stress’ in the patellofemoral joint in an in vitro study was 15% lower in an acute intervention when running without running shoes. It was NOT a clinical trial of barefoot vs shod running in those with patellofemoral pain syndrome which is what some in the crankosphere blogosphere are pretending it was in their comments on it!

    If you look at some of the comments on my review of the study a number of issues came up. With barefoot, the cadence is assumed to be greater, so there might be a 15% reduction in their model, but if you are taking more steps per minute barefoot compared to shoes, then you may not be getting a decrease in load at all as you are taking more steps!

    The authors showed that the reduction was due to angles of pull of tendons from less knee flexion in the barefoot condition, yet in the crankosphere blogosphere the comments being made by those who have not read the study were all about impact reduction when barefoot (duh?).

    Why did they get the decreased knee flexion? – it could be due to the barefoot; it could be due to the increased cadence when barefoot (and not actually due to the barefoot, as you can increase the cadence while wearing traditional shoes); it could also have been due to the forefoot striking (and not actually due to the barefoot, as you can forefoot or midfoot strike while wearing traditional shoes).

    Also keep in mind the comments that I keep making: you can’t decrease the load in one tissue without increasing it in another. The authors did not report on where the load/stress went. Kulmala et al showed that if you decrease the knee loads, you increase the ankle loads. To forefoot strike (ie barefoot run) you increase the forefoot and foot dorsiflexion moments and that exposes the muscles and tendons that cross behind the ankle joint axis and under the midfoot joints to increased stress and injury risk — ie six of one half a dozen of the other!

    This was actually a good study. More and more clinicians are looking at the cadence issues in patellofemoral pain syndrome. Barefoot drills may help facilitate that, but you can certainly do it without barefoot …. so no the study is NOT evidence that barefoot running is better.

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