Welcome to the Podiatry Arena forums

You are currently viewing our podiatry forum as a guest which gives you limited access to view all podiatry discussions and access our other features. By joining our free global community of Podiatrists and other interested foot health care professionals you will have access to post podiatry topics (answer and ask questions), communicate privately with other members, upload content, view attachments, receive a weekly email update of new discussions, access other special features. Registered users do not get displayed the advertisements in posted messages. Registration is fast, simple and absolutely free so please, join our global Podiatry community today!

  1. Everything that you are ever going to want to know about running shoes: Running Shoes Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
  2. Have you considered the Critical Thinking and Skeptical Boot Camp, for taking it to the next level? See here for more.
    Dismiss Notice
  3. Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
Dismiss Notice
Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
Dismiss Notice
Have you liked us on Facebook to get our updates? Please do. Click here for our Facebook page.
Dismiss Notice
Do you get the weekly newsletter that Podiatry Arena sends out to update everybody? If not, click here to organise this.

Interesting Evaluation of CoP progression in a caes study

Discussion in 'Biomechanics, Sports and Foot orthoses' started by David Smith, May 3, 2012.

  1. David Smith

    David Smith Well-Known Member

    Members do not see these Ads. Sign Up.
    Dear All

    I have a young woman who has presented with bilateral Achilles tendon pain but worse on the right and comes on during and after running. No running = no pain.

    I did an initial followed by a full biomechanical assessment evaluating the running and walking gait using clinical and biometric methods plus Templo 2D video and AM3 pressure mat mapping.

    Initially there appears to be a usual running gait of inverted forefoot/midfoot strike on the lateral foot followed by (close to) max pronation of the STJ thru the stance phase and resupination in propulsive phase.

    The unusual and interesting part (for me at least) is the action of the hip rotation versus the foot motion and what I would assess as its relation to a tendency to increased Ach ten stress.

    The right femur has a small internal torsion,this means there is a tendency toward a toe out abducted / internally rotated knee at initial contact and thru stance phase.

    At the reference start point of forefoot strike: What I see is that at forefoot strike the foot is only a few degrees toe out and a knee that continues to internally rotate and abduct thru to late midstance. The Hip abductors are weak and tend to allow the knee to do this during loading.

    At early propulsion the knee is facing inward approx 25-30dgs relative to the foot placement angle which is a few degrees toe out relative to the direction of progression. Therefore if the hip remained in this internally rotated position the swing of the right leg will progress across the left leg and of course inhibit the forward progression of the CoM in a straight line. Therefore the hip must start to externally rotate during the propulsive phase.

    This causes resupination of the STJ and rearfoot but also tends to move the CoP off the medial foot and onto the lateral forefoot, in so doing so this increases pronation moments about the STJ. The propulsive phase increases the load on the the Achilles tendon and the action of the Achilles tendon as it increases tension is to supinate the rearfoot. The torsion in the mid foot is increasing and so becoming stiffer but the need for the knee to be facing forward at swing phase is causing the hip to continue to externally rotate.

    At toe off (NB the knee does not achieve full extension and is about 8dgs-12dgs flexed at this point) the foot moves thru 30-33dgs of external rotation or abduction i.e. attaining 33dgs toe out at 33% of swing phase where the knee is at its greatest degree of flexion about 65-70dgs. The knee faces straight ahead and the swing phase continues and in late swing the hip internally rotates to allow a foot placement off toe out approximately 6-8dgs thus the GRF tends to exterally rotate the foot and pronate the STJ.

    This takes us back the the start point: The weak hip abductors and ext rotators allow the knee to internally rotate until the torsion at the knee between the moments of GRF and the opposing moments of CoM progression are balanced by the internal forces of the hip ext rotators, abductors and extensors, the CoM starts to rise and so the hip and knee start to externally rotate again.

    The CoPP transversely moves from lateral 5mpj to posterior to the 3rd MPJ the forward to the 2nd MPJ then back toward 3rd MPJ at propulsion


    Now this CoPP is not that much diferent to other forefoot strike running pattern, however in this case I thought it was interesting that it was probably the action of the hip muscles that was dominant in the resupination of the foot and the action of the hip muscles were probably greating increased by the rotation on the pelvis during contra lateral swing phase i.e. not just the concentric contraction of the hip musculature but also the eccentic contraction required as the pelvis rotates and tends to increase the muscle tensions, which tends to cause ext rotation of the knee and resupination of the rearfoot against the pronation tendency of the GRF.

    However when I take into consideration the position of the STJ axis, then the non w/b palpation of this shows a projection thru the 2nd interspace and one would imagine that as the foot pronates the STJ axis moves relatively medial. As the knee ext rotates and the foot resupinates then one can imagine that there seems to be some balance between the ability of the hip to ext rotate the knee, the resupination of the rearfoot and the position of the CoPP relative to the positon of the STJ axis projection thru the time of propulsion. I.E. it seems likely to me that the STJ axis projection and the CoPP follow or are allow to follow similar pathways inorder to maintain the optimal balance of the foot.

    Sorry to rattle on, maybe we've been over this kind of thing before, but I'm thinking out loud and thought it might be interesting to some. What are your thoughts. Be kind :empathy: or not :butcher:

    Regards Dave
  2. efuller

    efuller MVP

    I was doing a first read through and then got to the picture and had to make a comment. Achilles tendonitis and the heel never loads. That's your problem right there. The Achilles tendon is under a large amount of tension for the entire step. That's why it hurts. I'll go back and read the rest now. It seemed like there is some interesting stuff in there.

  3. Heel lift with varus post + gait retraining: increase stride length + decrease cadence + lean less forward on the torso: see if you can get her heels down/ loaded + PNF calf and hamstring stretches. Forefoot strike with achilles tendon problems is not a happy combination.

    P.S. ask her if she's changed her strike pattern recently because she's read on the internet that forefoot striking is "more natural" and/ or "results in fewer injuries". Seen dozens of them recently, some of whom had paid good money to "learn how to run":bang:

    P.P.S what's her habitual footwear? High heeled?
  4. David Smith

    David Smith Well-Known Member

    True enough, (and so galling that after all that time in analysis a couple of heel lifts might be all she needs DoH!:mad:) but I wasn't so interested in solving the pathology, although that's good too, but more just a good root thru the nature of the action going on thru that particular running gait style.

    Would it be useful if I could post a video?

    what's that? I think she naturally runs mid to forefoot strike, but it would be a good idea to ask that question. I agree mostly with the rest of your reply, I have found in the past that a couple of 6mm heel lifts can change a forefoot/midfoot striker to a rearfoot striker especially if they use running shoes with a deep heel.

    Attached is a good paper that considers these things.

    View My Video

    Regards Dave

    Attached Files:

  5. proprioceptive neuromuscular facilitation (PNF) stretching techniques.
  6. In the video attached she's at a very low speed and barefoot do you have a shod video. Also in terms of looking at strike position I find a sagittal plane film more helpful than a frontal plane one.
  7. davidh

    davidh Podiatry Arena Veteran

    Hi Dave,

    Agree with Eric.

    Is it a cavus foot presentation? The scans suggest so, in which case the equinus is unlikely to be due to her wearing high heels (unless she lives in them permanently).

    Bang a couple of heel lifts in, run her and re-evaluate.

    I wouldn't dream of suggesting any other treatment modality without actually seeing the patient, but I think that you may find posting forefoot valgus (to bring the ground up to the foot) in conjunction with heel lifts to be effective.

    The river Wye is running high and clearing, and there is a suggestion that salmon are running. I'm off for a couple of hours with the fly-rod;).
  8. David Smith

    David Smith Well-Known Member

    Simon The running is faster than it looks on the vid because the Tinypic upload is quite low resolution. She is runnning at 4.3mph and I find most people find 4-5mph about right and not many can go over 5mph. (that is the indicated speed on the treadmill what the actual speed is I have no idea 0mph relative to the ground frame of reference is spot on tho :wacko:)

    Strange! I find that the frontal plane is more useful and usually don't record the saggital side view just view it.

  9. RobinP

    RobinP Well-Known Member

    Ditto - not dozens but certainly quite a few
  10. RobinP

    RobinP Well-Known Member

    Just a thought relating to what Eric and Simon are saying

    I routinely evaluate patients who are walkers and I am generally assessing at 3.7-4.5 miles per hour.

    4.3 mph seems very low to be forefoot/midfoot striking. I would imagine that it is quite difficult to "run" at 4.3 mph and forefoot strike as it is closer to walking speed?
  11. It is a relatively low running speed, yet it is not so unusual to see runners forefoot striking when barefoot even at relatively low speeds. When shod, however, many will adopt a rearfoot strike pattern; not all but many. Hence a shod assessment might be helpful.

    It's a bit like doing a barefooted lunge test when the patient habitually wears shoes with a heel height differential- interesting but it's not a good reflection of the patients activities of daily living.
  12. RobinP

    RobinP Well-Known Member

    Apologies, didn't read that it was a pressure map, not in shoe pressure measure of course, barefoot at 4.3 mph would likely have a mid foot pattern.

    Agree that barefoot cop measures may not tell much if the shod strike pattern is completely different( or the same for that matter )
  13. David Smith

    David Smith Well-Known Member

    Simon and Robin

    Thanks for your continued input, I do also view the person running outside with shoes on and compare that to their running style on the treadmill as often the two can be completely different. In this case the indoor / outdoor & shod / unshod conditions are similar enough to be usefully comparable. Even running outside in shoes is extremely variable in the micro view i.e. the foot strike can go from a flat midfoot to a full forefoot.

    The reason I do not usually record saggital view is simply the problem of data storage and time to review all the data. I usually do barefoot and shod videos, walking and running if you add different views into that then the amount of data increases. So I choose the views I find most useful and record those, if I see something in another view that I think may be useful I will record that.

    So attached is a link to shod running on the treadmill and you will notice that the right foot in this clip often is slighlty rearfoot strike but this is an unrepresenatative bias of her more usual running style when running outside.

    View My Video

    Phew! parry and thrust, defend and justify its damn good exercise even to the point of catharsis

  14. For the record, 4 mph for running is slow. Even I can handle ten minute/ mile pace on a treadmill comfortably.

    Here's the miles per hour of the best of the best over given track distances:

    It's a couple of years out of date, but it gives you an indication. Even for the keen amateur, 4 mph is slow. Generally the keen marathoners I see are looking to hit around 4hours for 26 and a bit miles. At 4 mph 26 and a bit miles is going to take about 6.5 hours = slow.
  15. David Smith

    David Smith Well-Known Member

    Hey boys! enough with the fixating on the running speed already:eek: I don't know what 4.3 represents in actual velocity, the readout says 4.3M maybe its millipedes per millisecond, when the person who is running says that its fast enough then that is fast enough. Having said that, just to try it out I had a jog on it and foiund it quite confortable to jog at 6M and I'm well fat - so maybe it is miles per hour and all my customers a wimps. Even had an iron man triathelete the other day who thought 4.8 was fast enough so who knows :rolleyes: perhaps in future I just whack the speed up to 6M and watch them panic.

  16. efuller

    efuller MVP

    I find it interesting that there's been more discussion of the speed of the treadmill rather than thoughts on the mechanics. Maybe not everyone is understanding what you are saying about the mechanics. I'm having trouble trying to understand the terminology. Some of what I'm going to do is nit picking, but I'm a stickler for clarity

    If the heel never hits the ground, or barely hits the ground we lose the definitions of stance and propulsive phase. So, it's hard to understand from this wording what percentage of the step these things are occurring.

    I think you are saying that the mid point of her hip range of motion occurs when the knee cap is on the external side of the midline of the leg when viewed from in front. However, I'm not clear as to what you are saying after that. It would help to have a relationship. Bone relative to bone, or bone relative to ground, or bone relative to line of progression.

    Toe out, I get. That's the angle of the foot to the line of progression. So, is the knee going in relative to the foot or the pelvis? Do you mean knee abudcution, (motion of the femur relative to the tibia) or femur motion relative to the pelvis.

    If the heel doesn't hit the ground, then early propulsion would be right after contact. The first sentence otherwise is good except for understanding the timing. I don't understand the left leg right leg thing.

    I'd disagree with the increased load on the Achilles Tendon with resupination. Yes, there will be a greater pronation moment from the ground, but the STJ is supinating, so we know that supination moments from the leg are greater than the pronation moments from the ground. As the STJ supinates, you tend to get a shorter gear (as you shift the load laterally, onto the shorter metatarsals) there will be a smaller lever arm of ground reaction force opposing the achilles tendon at the ankle joint.

    I'm still not quite understanding how these transverse plane positions are going to put stress on the Achilles tendon which is pretty much a sagittal plane muscle.

    At foot contact, I'd agrue that you see STJ pronation (external foot rotation) because of the pronation moment from ground reaction force. In a forefoot striker, contact will tend to be quite far lateral to the STJ axis and most of the force will be vertical so center of pressure in the transverse plane will be creating much higher moments than in any other plane. So, it's not the ground reaction force causing external rotation of the foot that is causing pronation. It's the STJ pronation that is causing external rotation of the foot.

    I'm not convinced that hip musculature is dominant in anyone in causing motion at the stj. The knee is not that good of a torque translator. The trunk is not anchored in space. Yes there is some inertia, but any moment from the trunk on the femur will have an equal and opposite moment from the femur on the trunk.

  17. David Smith

    David Smith Well-Known Member


    Thanks for getting us back on track. I know what you mean about ambiguity but I've been trying to write something that is succinct and precise but it's impossible to describe relative positions and motions and not to ramble on with everything getting lost in a haze of confusion. So I've attached a document that does this quite well I think.

    So in my example there is a retrotorsion and so the knee is internally rotated when the hip is in its neutral position i.e. midway in its range of motion. I call this an internal femoral torsion and I think Kevin K first used that term as being less confusing than retrotorsion or anteversion. This results in a limited external rotation available in terms of the reference position of the knee which is determined as straight ahead.

    In this case it is unusual, in my experience, for the foot to maintain its position of reference i.e. in line with the knee and compensates with a malleolar external torsion. Therefore, in this case of internal femoral torsion (retrotorsion) when the knee is straight ahead the foot is toe out.

    Out of time for now

    Regards dave
  18. musmed

    musmed Active Member

    Dear Dave et al

    I looked at the history and video.
    I noticed in her video she hitches her left hip as seen by the slope of her clothing.
    Does she have a short left Quadratus Lumborum along with a very short right Tensor Fascia Lata?
    This will definitely produce the gait she has.
    Paul Conneely
    lovely day down here
  19. David Smith

    David Smith Well-Known Member


    Thanks for your thoughts, TFL and QL length are not something I directly measure. I do RoM testing of lower limbs and trunk which may indicate those things but I don't know how to isolate and test TFL successfully even tho I use Hazel M Clarkson's book -'Musculoskeletal assessment Joint RoM and Manual Muscle strength' it is not very clear.

    Eric, Regarding knee internal rotation and abduction and how it affects progression of gait, foot posture and CoPP:

    For the purposes of this discussion the knee joint does not have frontal plane RoM and the articulating surfaces of the femoral condyles and the tibial plateau remain anatomically congruent.

    Therefore if the patella is observed as being internally facing then this is due to
    1) internal rotation of the hip or 2) Femoral torsion i.e. a retrotorsion or anteversion or 3) all of the former. Can we call this internally facing knee position and internal rotation of the knee - I believe it is useful for our purposes.

    If the knee appears to have a genu valgum (knock knee) and it is not an anatomical variation, then this is due to a combination of knee internal rotation (position) and flexion plus hip internal rotation and adduction and is only an illusion of genu valgum. So as the knee extends and the hip externally rotates the knee must return to its normal anatomical position of reference (for the subject being observed). In the case we are discussing the hip returns to the neutral (midrange) position and due to the internal femoral torsion the knee is 'normally' internally facing a few degrees.

    Assume that in this position the foot placement is straight ahead, then in that case hip flexion will result in a directly forward progression of the foot. However if the observer sees an apparent genu valgum then flexion of the hip will result in the foot progressing diagonally toward the contralateral foot.

    Therefore it is bot necessary and unavoidable that the knee should return to its anatomical position of reference to attain optimal progression of the foot.

    The affect of these positions and change of positiont thru the gait cycle will impact on CoP progression and the nature and position of GRF acting about joints of interest such as the STJ and so will or may significantly affect the foot posture and the consideration of orthotic design.

    More later got customers to see to.

    Dave Smith
    Last edited: May 9, 2012
  20. David Smith

    David Smith Well-Known Member

    I would contest that to some degree because at forefoot strike the foot in inverted and supinated so 2 things have occured to reduce the moment arm available to GRF about the STJ. 1) the more inverted position attained the shorter the moment arm and if you could invert the foot by 90 dgs then potentially the moment arm is zero. 2) the foot is supinated so the STJ axis is rotated toward its maximum lateral position. Therefore at forefoot strike the moment arm available to VGRF is at its shortest. Whereas the moment arm available to horizontal A-P (anterior-posterior) GRF is at its longest because the foot is plantarflexed plus, if the foot is toe out placement then the magnitude of A-P GRF available to cause STJ pronation moments is greater. So typically A-P GRF is 15%-20% of VGRF but the moment arm available to A-P GRF may be 6-8 times longer, so potentially the A-P GRF could produce the same or greater magnitude of moments about the STJ as VGRF except that with a 10dg toe out only the sin of 10dgs =>0.17 x A-P GRF is available to cause pronation moments. Even so this could still represent moments due to A-P GRF = 20% of those due to VGRF, which is a significant consideration.

    As far as the last part of your statement goes, this is a bit of a chicken and egg scenario because if as you say the foot is pronated by VGRF and so externally rotates the as external rotation occurs and as A-P GRF increases then torque that externally rotate the foot also increases. This is made clear in research that indicates forefoot striking shows increased y axis (vertical or in the axis of the long bones) moments (torque) about the knee.


    Regards Dave
  21. efuller

    efuller MVP

    I don't really like using the patella as the defining point of the knee. The patella is a single point and you are trying to describe an angular relationship. In the document you posted it was interesting to see that one of the two lines that made up the femoral torsion measurement was a line connecting the posterior surface of the medial and lateral condyles. Functionally, the "bottom of the femur" could be the knee joint axis of motion. The relationship of the knee axis of motion to the frontal plane of the body is what I think we are actually talking about when we discuss patellar position.

    The internal position of the knee (the axis of motion of the knee joint is internally rotated relative to the frontal plane of the body) can be caused by all of those things that you mention, but the distinction is rarely made clinically. So, internal rotation of the knee is an acceptable way of describing this.

    I've got no problem with the first half. In the second half are you talking about as the knee extends, the apparent genu valgum must disappear because visually moves in the frontal plane from more medial to lateral. However, this is not necessarily transverse plane motion.

    The hip is a ball and socket joint. When you describe flexion of the hip above, you appear to be assuming that the motion is constrained to pure sagittal flexion. It could move anywhere, because it's not constrained. The person could choose to move his hip in such a way that he does not move the foot toward the other foot.

    I'm not sure that orthotic design will affect much beyond the foot. There may be some foot changes that effect knee and hip motion. It is an interesting question as to how much orthotic design changes will effect more proximal joints. I can see how center of pressure changes can effect knee joint frontal plane moments. What other major effects to orthotic variables have on more proximal joints?

  22. David Smith

    David Smith Well-Known Member

    So my point here is that as I considered the CoPP as characterised by the pressure mat I was wondering how significant was the influence of the excursion of the knee on the CoPP thru the stance phase. How would my orthotic design change with this in mind and would interventions designed to change or control the knee excursion be beneficial in terms of distal pathology e.g. hip abductor, external rotator strengthening.

  23. David Smith

    David Smith Well-Known Member


    Of course you are right in theory but in reality the constraint comes from the musculature e.g. standing normally with feet approximately straight ahead, flex the hip. You should be able to flex to 90dgs easily enough. Now internally rotate your hip and then try to 'flex' your hip straight in front of you and you wont get past 30dgs or so. But if you now try to 'flex' your hip diagonally in the direction your knee is pointing, then you will attain 90dgs again. Therefore there is a preferred pathway, easiest route of progression in which the limb will tend to proceed but of course there can be a concious or sub concious decision to override that tendency. However in that case trick movements may result in overuse pathology of muscles.

  24. efuller

    efuller MVP

    I replied

    Now I see where you are coming from. I can see anterior to posterior force contributing less than 30% (And maybe a lot less) of the pronation moment from the ground in out toed running. However, the original question was what this has to do with Achilles tendonitis. STJ motion produce much less tendon excursion than ankle joint range of motion. Especially if you look at the relative amounts of motion that actually occur.


Share This Page