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Muscle strength and posterior tibial tendon dysfunction

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Sep 10, 2008.

  1. NewsBot

    NewsBot The Admin that posts the news.


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    The Effect of Stage II Posterior Tibial Tendon Dysfunction on Deep Compartment Muscle Strength: A New Strength Test.
    Houck JR, Nomides C, Neville CG, Samuel Flemister A.
    Foot Ankle Int. 2008 Sep;29(9):895-902.
  2. Craig Payne

    Craig Payne Moderator

    What they were really doing is comparing a group of people with a medially located STJ axis (the PTTD group) to a group who probably did not have a medially located STJ axis (the control group) .... of course there will be apparent (and maybe not even real) strength deficits due to the lever arm that the posterior tibial muscle has to the STJ axis!
  3. Admin2

    Admin2 Administrator Staff Member

  4. CraigT

    CraigT Well-Known Member

    Hey Craig
    Good point, however isn't a large component of the cause of the medially deviated STJ axis the fact that the foot is weight bearing? ie: as the foot moves into a pronated position, the STJ axis moves medially. This is a NWB test...
    I would think that the weakness is there (ie is real rather than apparent), and may be caused by the everyday poor function of the tib post for all the reasons you just mentioned.

  5. Craig and Craig:

    A few things here are important to remember. First of all, any muscle strength testing protocol does not test only the ability of the muscle-tendon unit to produce a change in tensile force. Rather "muscle strength testing" is also testing the moment arm of that muscle-tendon unit relative to the joint axis that is being used to test the muscle. So, when we say we are "testing muscle strength", that is really not the case. What we are testing is "testing muscle-induced moment" about a joint axis. I think this important concept is very poorly understood in all medical disciplines, and even within the international biomechanics community.

    This factor is especially important at the subtalar joint (STJ) axis where there are such small moment arms and also such a large variation in STJ moment arms for the invertors and evertors. Take, for example, the posterior tibial muscle. In the patient that has a medially deviated STJ axis, the moment arm during weightbearing for producing STJ supination moment may be in the order of 5 mm whereas, in the normal shaped foot the supination moment arm is in the order of 20 mm and in the laterally deviated STJ axis, the supination moment arm is in the order of 30 mm. In other words, for a given absolute muscle-tendon contractile tensile force, the medially deviated STJ axis could have a six-fold decrease in "posterior tibial muscle strength" when compared to a laterally deviated STJ axis.

    I challenge anyone to describe to me any other muscle-joint combination in the human body that can have such large relative changes in muscle moment arm lengths from one individual to another. This is one of the reasons why the concept of understanding STJ axis location is so significant and so important for the health professional that treats foot and lower extremity mechanically-based pathology.
  6. Dananberg

    Dananberg Active Member

    Kevin wrote "I challenge anyone to describe to me any other muscle-joint combination in the human body that can have such large relative changes in muscle moment arm lengths from one individual to another."

    How about the piriformis in subjects with substantial leg length difference and pelvic rotation. Another would be the VMO (quad) in subjects with genu varum, and/or genu valgum. Rather high changes in moment arms result in these muscles with the anatomical variations across different patients.

    There are many factors which can subject some to decreased strength in the posterior tibial muscle. Kevin is clearly correct with respect to muscle moments and STJ axis deviation....but this is just not the only reason why dysfunction occurs. In fact, I have seen several cases of PTTD in which the posterior tibial muscle exhibits normal strength, while the peroneals are markedly inhibited. Change peroneal strength improves heel lift function, and can decrease stress to the posterior tibial.

  7. Howard:

    I don't think that there are as significant changes in hip joint axis moment arm for the piriformis or as significant changes in knee joint axis moment arm for the vastus medialis obliquus (VMO) as there are for the subtalar joint (STJ) axis for the posterior tibial tendon. The posterior tibial tendon can have a moment arm for supination that is as much as (if not more) 6 times longer in the foot that has a laterally deviated axis than the moment arm for supination is in the medially deviated STJ axis foot. I don't think the piriformis or VMO have magnitudes of change in muscle moment arm lengths that are even close the posterior tibial tendon for their respective joint axes. This large change in PT tendon supination moment arm length to the STJ axis is caused by the insertion of posterior tibial tendon being on the navicular and the wide range of possible range of adduction/abduction motion of the navicular relative to the talar head, where the STJ axis passes superiorly out of.
  8. Dananberg

    Dananberg Active Member


    I guess that even in these tough economic times, its good to know there are some things that remain reliable. The nature of our conversations are like they have never changed.

    I was really thinking about the effect of the piriformis on the sacroiliac (SIJ) joint, and not the hip. If the rotation of the pelvis is forward, and guarding pain via hip flexion is the gait style, then the effective difference is highly significant, and can disable many with lower back pain. Prehaps you are correct, that the PT/STJ is greater, its really splitting hairs. What's far more important is the reason why the PT muscle weakened itself to begin with. This is a discussion for another day.

    As far as the VMO goes, patients with terrible knee pain often walk with a large component of midstep flexion at the knee during weight bearing. When the
    30-40 degree flexion stress is added to the varus/valgus equation, then one could argue that the moment arm stress point may be close to that of the PT/STJ as well.

    I do accept your point though, that the stress on the PT tendon in a foot with a medial deviation is far greater than without, and the greater the deviation, the more stressful it is for the tendon.

  9. Howard:

    I don't have much fun discussing things with people that are always in agreement with me. I'm sure we will be having discussions for many years to come.;)
  10. efuller

    efuller MVP

    I don't know how to measure relative lever arms but here are a couple of things to think about.

    The interossei muscles can turn from plantar flexors to dorsiflexors depending on position of the toes. A non reducible dorsiflexion contracture of the MPJ could keep these muscles as dorsiflexors.

    Also the anterior tibial can change from a pronator to a supinator of the STJ depending on STJ position and STJ axis position. Although the anterior tibial will still maintain its function of a dorsiflexion of the ankle regardless.


  11. The anterior tibial tendon to subtalar joint (STJ) axis relationship certainly rivals that of the posterior tibial tendon to STJ axis. But since the STJ axis is involved in both of these muscle to joint axis changes, then my point remains the same....the STJ axis displays some pretty impressive changes in muscle moment arms from one individual to another and throughout its normal range of motion......much more than any other joint in the body that I know of.

    I'm not too impressed about the range of movement of the interossei across the metatarso-phalangeal joint axis....even though it there is definitely some changes that occur.
  12. nelsandr

    nelsandr Member

    I appreciate Kevin’s comments regarding the medial/lateral location of the subtalar joint axis with regard to the posterior tibialis tendon muscle strength, and in reference to his article in 2001 about the subtalar joint equilibrium theory. So what really is being discussed is not so much an element of muscle strength as it is a discussion about mechanical advantage. A medially located subtalar axis would have a decreased mechanical advantage for the posterior tibialis, thus requiring it to work harder to do the same amount of work that a more laterally (or as you call it “normal”) located axis would require.

    However, one concept that I feel really escapes the discussion is not so much about muscle strength, which usually is describing a muscle action, which is usually describing a NWB test. What the discussion and research really needs to start focusing on is what the muscles FUNCTION is. In this example of the posterior tibialis one primary element of the muscle test used was inversion. However, the posterior tibialis primarily functions in WB as a decelerator (i.e. eccentric) controller of eversion and dorsiflexion. Reber (1993) started a discussion about this with the posterior muscles of the calf (rather than them being called the plantar flexors).

    Clinically, a discussion of mechanical advantage is relevant to the function of the posterior tibialis. However a discussion that focuses on a non-WB test that encourages non-functional muscle contractions is really not that relevant.

    Andrew Nelson, PT
  13. NewsBot

    NewsBot The Admin that posts the news.

    Effect of eccentric exercise program for early tibialis posterior tendinopathy.
    Kulig K, Lederhaus ES, Reischl S, Arya S, Bashford G.
    Foot Ankle Int. 2009 Sep;30(9):877-85.
  14. NewsBot

    NewsBot The Admin that posts the news.

    Deep Posterior Compartment Strength and Foot Kinematics in Subjects With Stage II Posterior Tibial Tendon Dysfunction.
    Neville C, Flemister AS, Houck JR.
    Foot Ankle Int. 2010 Apr;31(4):320-8.
  15. NewsBot

    NewsBot The Admin that posts the news.

    Modified strength testing protocol for use in subjects with posterior tibial tendon dysfunction
    Cady, J., Noffey, J., Neville, C.
  16. NewsBot

    NewsBot The Admin that posts the news.

    Ultrasound Imaging Is Reliable for Tibialis Posterior Size Measurements.
    Johnson AW et al
    J Ultrasound Med. 2020 May 15

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