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Knee abduction impulses and patellofemoral pain

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, May 31, 2006.

  1. NewsBot

    NewsBot The Admin that posts the news.


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    Knee Angular Impulse as a Predictor of Patellofemoral Pain in Runners
    May 30, 2006 American Journal of Sports Medicine
  2. Admin2

    Admin2 Administrator Staff Member

  3. Craig Payne

    Craig Payne Moderator

    I have a graph I use often from one of Beno Nigg's studies that shows that medial foot wedges increase the knee adduction moment in about half the subjects and decreased it in the other half.

    An increased knee adduction moment is the numero uno risk factor for medial compartment osteoarthritis in the knee....now its a shown in the above study abduction moments are found to be associated with in patellofemoral pain.

    Does it not scare anyone else that foot orthoses may be increasing the knee adduction moment in half the people we use them in?
  4. Atlas

    Atlas Well-Known Member

    "Beno Nigg's studies that shows that medial foot wedges increase the knee adduction moment in about half the subjects and decreased it in the other half."

    Medial (high side medial) rearfoot wedging either inverts the rearfoot (motion) and/or increasing supination force to the STJ (forces). I can't see how this could do anything other than increase knee adduction moments. IMO, time and further research will change the accepted 50/50 to more 95/5.

    Hence your fear should be twofold Craig, in that your mandatory Blake/DC-wedge will undoubtedly increase medial compressive forces in the knee.

    The good news is that the medial knee joint is only one source of knee symptoms.

    My old fear was that every sports trainer at every suburban football field was strapping the STJ of most footballers in extreme end-range pronation. This was done for their most physical hours of the week. Yet the ramifications were marginal. That is why I was not too suprised at your simialr finding that lateral wedging had no negative sequale after 1 year. I can't work it out, but I am not suprised.
  5. David Smith

    David Smith Well-Known Member

    Craig and Atlas

    Do you think that when examining changes in moments about a certain joint of interest, eg the knee, errors of interpretation can occur when it is not clear about the orientation and evaluation of global and local axes.

    For instance in the study 'Knee Angular Impulse as a Predictor of Patellofemoral Pain in Runners' It is not clear in the abstract which axis system is being refered to or the orientation of the moments discussed ie internal or external. Niether is the rotational reference defined.

    To define the axes I am refering to the global X axis is anterio-posterior and is positve in the direction of walking and the Z axis is medio-lateral and positve in value from left to right. The Local axis of the knee = Z axis the medio-lateral bisection of the tibial condyles and the X axis orthoganal (at right angles) to the Z axis and bisecting the intercondylar prominence.

    In 'normal stance these two axes systems will be congruent (probably).
    However in the toe out gait the knee will be externally rotated to some degree. For arguments sake lets say 30dgs. In this case moments about the knee local axis is unlikely to be the same as the global axis. The negative X GRF (30% B/w max) in the toe out case will have a significant effect on the abduction moments about the knee (rotational reference is the distal limb). Now fit some orthoses medially posted and the same person now has a reduced toe out gait, lets say it is now zero dgs, the negative X GRF now has only knee flexion moments and produces no abduction of the knee.

    If the researcher was defining moments about the local axis then there would have been a large reducion in abduction moments or a relative increase in adduction moments. This however is only an analysis of the external moments. Internal adduction moments resisting external abduction moments may have been pathologicaly high and therefore increasing external adduction moments may be benificial to the knee.

    Conversely if the gait foot placement was straight ahead and the knee internally rotated with pronation then the negative X GRF will be causing some adduction of the knee local axis and fitting orthoses with a medial post may stop the knee from internally rotation and therfore there will be less adduction moments applied to the knee by negative X GRF.

    Hope this makes sense as I've quickly bashed this out before going to Judo.

    Cheers Dave Smith
  6. dingo

    dingo Member

    can you please explain how medially posted orthotics increase the knee adduction moment
  7. admin

    admin Administrator Staff Member

    There may be an explanation in the thread on lateral wedges and medial knee OA as lateral wedges decrease the adduction moment.
  8. dingo

    dingo Member

    Maybe I have got something wrong in my thinking here so I would appreciate any advice to correct me. I am thinking, abduction, being movement away from the center line, and adduction, movement toward the center line, therefore would the abduction moment of the knee not involve the movement of the knee away from the center line and the adduction moment movement toward the center line. And as such would medial wedging not increase the abduction moment and lateral wedging increase the adduction moment. Please advise, Nick
  9. Nick:

    It can be very confusing when talking about moments at joints since there are such things as external moments, or those moments occurring external to the joint (such as that from ground reaction force), and also internal moments, or those moments occurring inside or around the joint.

    Let's use an easy example. If you hold you arm out straight, with your elbow extended and palm of hand facing superiorly, and put a 5 lb weight in your hand, there are both external elbow moments and internal elbow moments. There would be an external elbow extension moment from the mass of the forearm being accelerated by gravity downward and there would also be an additional external elbow extension moment from the the mass of the weight in your hand being accelerated by gravity.

    We know, that if the elbow is not accelerating, that rotational equilibrium at the elbow has occurred. In order to have rotational equilibrium, the moments in one direction must exactly counterbalance the moments in the opposite direction. Therefore, since we know that the mass of the arm and the mass of the weight in your hand are causing external elbow extension moments then we also must know that there are internal elbow flexion moments that are simultaneously occurring. These internal elbow flexion moments may be caused by joint compression forces, ligamentous tensile forces and/or by muscular contractile forces (e.g. biceps muscle) acting to cause a tendency to flex the elbow, and, therefore, resist further elbow extension.

    In the case of a medial or varus wedge placed plantar to the foot, the center of pressure (CoP) from ground reaction force (GRF) will be shifted medially on the plantar foot which will, as long as the direction of the GRF vector hasn't changed also, will make the GRF vector more medial (or less lateral) to the knee joint. This varus wedge will therefore cause the following to occur:
    1) An increase in external knee adduction moment (or decrease in external knee abduction moment) and,
    2) An increase in internal knee abduction moment (or decrease in internal knee adduction moment).

    The increase in external knee adduction moment will be directly caused by the medial shift of the GRF vector relative to the knee joint. However, the increase in internal knee abduction moment will be caused by the internal joint compression forces, ligamentous tensile forces and muscular contractile forces that all combine together to resist the tendency for the knee to undergo adduction motion with the placement of the varus wedge under the foot.

    You must realize that if an externally applied moment is placed across a joint axis and the joint does not move as a result, that internal moments must have been also created at the same time at the joint level to resist these applied external moments. This forms the basis of my discussion above regarding the elbow and knee and in my previous publications on the kinetics (including the concepts of rotational equilibrium) of the ankle joint, subtalar joint, midtarsal joint and metatarsophalangeal joints.

    I hope that this makes sense of this sometimes confusing subject. If you want a more complete explanation with illustrations, I have written about these concepts previously in my October 2004 Precision Intricast Newsletter, "Foot Orthoses for Medial Compartment Osteoarthritis of the Knee". I will be happy to e-mail this newsletter to you privately if you provide me your e-mail address.
    Last edited: Jan 21, 2007
  10. trophikas

    trophikas Active Member

    Gday Kevin

    I would love a copy of this article as Im having trouble getting my head around this subject. My email is tarakancottage@hotmail.com. Would you ever use a medial wedge to treat PFPS? I currently have a patient who has a 2 yr history of LHS (Left Hand side) PFPS and LHS SIJ pain. The symptoms always occur when she hits the 12/15 km mark. She tried motion control shoes and they resolved symptoms in her LHS knee/SIJ BUT created the same symptoms on her RHS. She was then placed in a set of neutral runners which got rid of the RHS pain but then the LHS pain returned. She saw a physio who gave her glut strenthening exercises which she has been diligent with for last 6 months but no reduction in Symptoms. I have given her some temporary full length med wedging in her LHS shoe only (As motion control shoes reduced symptoms on this side) and advised Re: vast med exercises and ITB stretches. I am running with her next wk after she is fatigued to view her technique. Do you have any treatment pearls that may be pertinant for this patient. She is a fit active 40 y/o Indian female, no crepitus through ROM in knee. Will the use of med wedging predispose her to med COMP knee O/A and exaserbate her Symptoms? If so why did the motion controll shoes, which essentaill are medially wedging her, reduce symptoms?


    Last edited: Aug 23, 2007
  11. Gday Marty:

    What article are you speaking of? I would be happy to e-mail this article to you if I only knew what this article was. ;)

    I have used varus wedged orthoses to treat patellofemoral syndrome (PFS) for the past 20+ years. These patients seem to also respond to the addition a forefoot varus extension to their orthosis in many cases.

    With your patient, have you considered having her wear her neutral shoe on the right foot and motion control shoe on the left foot. I am serious about this suggestion. This "different shoe on each foot suggestion" does make sense given her history, and she may just need to tell everyone that she was formerly a high-jumper and couldn't ever give up the "different shoe habit". :rolleyes:

    Adding a varus wedge will increase the external subtalar joint (STJ) supination moment from ground reaction force by moving the center of pressure (CoP) on her foot more medially. This should decrease the internal tibial, knee and femoral rotation that is suspected to be the cause of PFS. There are multiple research papers that now demonstrate that foot orthoses affect both the kinetics and kinematics of the knee during running.

    It is very difficult to cause medial knee compartment osteoarthritis (OA) with orthoses unless the patient already has preexisting medial knee OA to start with. By the way, medial knee OA and PFS generally have very different presentations on physical examination, if you are up on your knee examination techniques.

    Hope this helps.
  12. trophikas

    trophikas Active Member

    Gday Kevin

    Thankyou for your reply to my post. The article I was refering to is the one on "Foot Orthoses for Medial Compartment Osteoarthritis of the Knee". My understanding of diagnosing knee pathology is sadly limited so could you give me a brief overview on how to clinically differentiate med comp o/a from PFPS. :confused:
    Your suggestion about the patient wearing a different shoe on each foot is great :D , something so obvious that I never would have thought about it! I would also appreciate any copies of articles you have lying around that support the use of orthosis for treating PFPS, cuase everything that Iv read so far has refuted this (aside from in patients with F/F Varus). I believe there is currently a study underway at the University of Queensland testing this hypothesis using OTC Vasyli devices, but I may be wrong.

    I have also read on the forum recently some discussion of running technique. I was wondering if there were one two key things that I should be looking for. I understand that hip adduction and internal rotation, weak gluts, tight ITB are all risk factors for PFPS. So I presume that after my patient begins to fatigue at the 12/15km mark (when she usually experiences pain) I will see an increase in patellar squinting and perhaps excessive hip drop on her symptomatic side. I have also advised her to not run down hills and to push hard up hills as well as substitute 1 or 2 of her endurance sessions with interval training on flat surfaces and doing hill work (running 75% up hill focussing on keeping good running form). How does this training modification sound to you? Her goal is to run half marathons pain free!

    Thankyou for your help :)

  13. conp

    conp Active Member

    Hi All,
    I have not been following this thread Or the lateral wedges thread for treatment of medial knee pain HOWEVER I just briefly read through both threads. So sorry if I go over old ground.

    Firstly, if we assume from research that both knee adduction moments and knee abduction moments can be significant factors causing medial OA knee pain...... then TO SOME EXTENT...I think this answers the question why for some people valgus wedges work for medial knee pain and for the others, varus wedges. AND THIS IS WHY ALL THE STUDIES ARE GOING AROUND THE SAME CIRCLE AS BOTH THESE TREATMENT METHODS ARE NOT ALWAYS applied to the 'correct' patients.

    My thinking is that there are basically (for simplicity's sake) two types of medial compartment OA of knee.
    1) Supinated, genu varum type
    2) Pronated, genu valgumtype

    The 1) type has medial OA knee pain due to knee abduction moments. (assuption on my behalf)
    The 2) type has medial OA knee pain due to knee adduction moments.( again assumption)


    The key is find is to make sure you are increasing knee adduction in the 1) type and to increase knee abduction in the 2).
    How can we be sure that the varus or valgus wedge wedge abducts or adducts knee????
    I have a theory relating mainly to STJ position BUT AS I have made so many ASSUPTIONS ALREADY (mainly for simplicity's sake) I will sign off!!
    Last edited: Aug 24, 2007
  14. Gday Marty:

    The newsletter has been sent to your e-mail address. Hope you enjoy it.

    For knee examination technique, I would suggest the following book: Physical Examination of the Spine and Extremities. Basically, medial knee OA will tend to have medial joint line pain at the knee with periarticular ridging (osteophytes) and possible asymmetrical genu varum deformity whereas patellofemoral pain syndrome (PFPS) will show pain in the peri-patellar region.

    Regarding the therapeutic effectiveness of foot orthoses for PFPS, you should read the following paper (Eng JJ, Pierrynowski MR: Evaluation of soft foot orthotics in the treatment of patellofemoral pain syndrome. Phys Therapy, 73:62-70, 1993).

    And finally, regarding your patient's training, I think if you focus on orthosis-shoe biomechanics with this patient, that she will be able to run her half marathon. However, many female runners in this age group have relatively weak thigh-leg muscles and getting them to cross-train on a bicycle-trainer or elliptical trainer to increase leg strength often helps....but this takes time (i.e. months) ......and they often don't want to take time to make up for their lack of a prior sedentary lifestyle in order to be a better runner.
  15. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Kevin,

    I don't feel at this stage I am up to scratch with examining the knee. I would be very grateful if you could illustrate what asessments your perform during a knee examination.

    Kind Regards,

  16. Here is what I wrote earlier.....

    .......it still applies two months later.....get the book...read it over....then get a friend that is not too fat to practice on so that you can easily palpate the osseous landmarks of the knee....there is no better way to get acquainted with the largest joint in the human body.
  17. Daniel Bagnall

    Daniel Bagnall Active Member

    Thanks Kevin
  18. NewsBot

    NewsBot The Admin that posts the news.

    High- compared to low-arched athletes exhibit smaller knee abduction moments in walking and running.
    Powell DW, Andrews S, Stickley C, Williams DS.
    Hum Mov Sci. 2016 Oct 13;50:47-53. doi: 10.1016/j.humov.2016.10.006.

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