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Question about supinated but mobile foot

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Ann PT, Aug 22, 2014.

  1. Ann PT

    Ann PT Active Member


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    Hi all,

    I have a 46 y.o. woman with chronic intermittent lower calf pain sometimes extending down into her Achilles. She stands with at least 10 degrees of calcaneal inversion bilaterally. Subtalar joint neutral position is:

    Right: vertical heel, semi-rigid to rigid plantarflexed 1st ray (can't push it up fully to be even with 2nd)
    Left: 25 deg calcaneal varus with mobile plantarflexed 1st ray

    In gait she stays supinated throughout the entire stance phase. She also has hypermobility at her ankles (positive anterior drawer but no history of ankle sprains) and hypermobility at the midtarsal joints bilaterally
    My question is- why is her hypermobile foot staying so supinated? Is her gastroc just overworking to stabilize the hypermobility? I've seen plenty of hypermobile feet do just the opposite- flatten like a pancake in weightbearing- which seems like the path of least resistance the body would take. Are her gastrocs fighting this path of least resistance and why?

    Thanks,
    Ann
     
  2. footdoctor

    footdoctor Active Member

    Hi Anne.

    I would look at the axis of the STJ. Chances are her STJ axis is laterally located.

    Try a supination resistance test, low resistance to supination will give you the answer.

    I would hesitate a guess that its her peroneus longus that's problematic too.


    Scott
     
  3. Ann PT

    Ann PT Active Member

    Hi Scott,
    Thank you for the reply.

    What do you mean by "problematic" in regards to her peroneus longus?

    Ann
     
  4. footdoctor

    footdoctor Active Member

    Sorry Ann

    By problematic i really meant dysfunctional.

    How is peroneal muscle strength?

    Any trigger points in muscle belly of PL?

    Scott
     
  5. Ann PT

    Ann PT Active Member

    Peroneals are 5/5 to MMT and no trigger points palpated...
     
  6. efuller

    efuller MVP

    I would agree with thought about STJ axis having a lateral position. In a foot with a much more laterally deviated STJ axis than average, ground reaction force will cause a supination moment. When the ground is attempting to supinate the foot, the body will try and prevent that by using the peroneal muscles. Have you read Kevin Kirby's rotational equilibrium paper? The constant use of the peroneal muscles will cause a pain and or fatigue up the lateral side of the leg. Is that what your patient is feeling. If there is a laterally positioned STJ axis, these people will often feel better, almost immediately, with valgus wedging.

    The gastroc is an interesting muscle. It's main role is to plantar flex the ankle joint. It is inserted medial to the STJ axis so at the same time it is plantar flexing the ankle, it will tend to be supinating the STJ. However, when it plantar flexes the ankle the Center of Pressure of ground reaction force is shifted anteriorly. With an average STJ axis location a forward shift of the center of pressure will tend to create a pronation moment that will offset the direct supination moment from the Achilles tendon. So, if you have a lateral STJ axis, you won't get increased pronation moment from ground reaction force and there will be a lot of source of supination moment and the only source of pronation moment might be the peroneal muscles.

    I hope this helps.

    Eric
     
  7. Ann:

    I'm having difficulty following your description but both feet appear to be inverted at the calcaneus in relaxed calcaneal stance position.

    Here are the proper tests to perform on this foot:

    1. Determine subtalar joint (STJ) axis location while non-weightbearing and weightbearing.

    2. Test peroneus brevis and peroneus longus muscle strength separately from each other to rule out weakness/neurological disorders of each of these pronators of the STJ.

    3. During relaxed bipedal stance it is less important to determine where the heel bisection line is relative to the ground and more important to determine where the STJ is within its range of motion (i.e. its rotational position). In other words, is the STJ neutral, or supinated or pronated from neutral and by how many degrees supinated or pronated from neutral or how many degrees supinated from the maximally pronated position are the feet during relaxed bipedal stance?

    4. Perform the maximum pronation test to help out with test #3.

    5. Perform the supination resistance test to better determine the prevailing balance of internal pronation/supination moments acting on each foot.

    6. During relaxed bipedal stance check the peroneal tendons to see if the peroneal muscles are tonically active, (which they probably are if I understand your clinical description correctly).

    7. Determine the exact anatomic location of the patient's fatigue. My guess, as Eric Fuller noted, the pain is probably in the peroneal muscles and is due to chronic peroneal muscle fatigue and over-activity of her peroneals due to her laterally deviated STJ axes. A 5 degree forefoot and rearfoot valgus wedge placed inside her shoe should make her less asymptomatic nearly immediately.

    Please let us know what you find and clinical photos and patient followup posts from you would be very helpful for everyone else following along.:drinks
     
  8. Ann PT

    Ann PT Active Member

    Thank you very much, Eric and Kevin, for your input and questions. I will try to answer as many of Kevin's questions as I can after I see the patient again on Tuesday. For now, I have a couple questions for you, Kevin.

    1. How do you determine the STJ axis in weightbearing?
    2. I have no reason to believe there is any neurological disorder and the patinet's peroneals tested 5/5 to MMT as described by Florence Kendall et al. How do you test the brevis v. longus separately? If they are both innervated by the superficial peroneal nerve, and serve the same function, how can you separate contraction of one from the other? Do you have a method of quantifying depression of the first metatarsal head?

    I will also send a picture of the patient pointing to where her symptoms are located. It appears to me she is pointing medial and lateral to her achilles tendon. At her last visit, her pain to palpation appeared to be primarily in the area of her posterior tibialis muscle but I will recheck this as well.

    I also believe she has a lateral STJ axis but will try to determine by Kevin's method. I have never been able to master this and trust my reliability and validity but I'm still trying!

    Thanks again!

    Ann

    P.S. Yes, Eric, I have read Kevin's paper and I reread his 3 volumes of newsletters frequently when treating patients with foot problems.
     
  9. Here is the way I described finding the STJ axis in a weightbearing foot in my clinical skills handout that I made up for my North Queensland, Australia workshop last week [see my photo below performing this technique at a seminar in Madrid, Spain in February 2011]:

    To test for the peroneus brevis, I place the palm of my hand on the lateral aspect of the forefoot with me observing for or using one of my hands to palpate for tension or bowstringing in the the peroneus brevis tendon while having the patient evert against resistance against my hand on the lateral aspect of the forefoot.

    To test for the peroneus longus, I place the palm of my hand on the plantar aspect of the first metatarsal head with the ankle dorsiflexed to about 90 degrees and then tell the patient to plantarflex and evert their foot against my hand under their first metatarsal head. There is no other muscle that can plantarflex the first ray, plantarflex the ankle and evert the foot...only the peroneus longus can do that. (Gastroc-soleus will plantarflex the lateral column, but not necessarily the first ray. If the peroneus longus is weak with a strong gastroc-soleus muscle, the first metatarsal cannot normally resist strong force from the examiner's hand on the plantar aspect of the first metatarsal head when testing for ankle plantarflexion strength.)

    Ann, here's the description of the non-weightbearing method of STJ axis determination I have in the clinical skills workshop handout described above:

    Photos would be helpful in addition to trialing her in a rearfoot and forefoot valgus wedge in the office as I described earlier. If you can do a gait video, that would be even better!

    Good luck.:drinks
     
  10. Ann PT

    Ann PT Active Member

    Ok...here goes...hope these pictures and videos come through ok. I have a front and rear view of relaxed calcaneal stance, a video of her walking and a video of her doing the max pronation test. The lines around her achilles tendon are her chief areas of pain (L>R) which she feels when getting out of bed or after being sedentary. The lines higher up her leg are where the pain can move to with a lot of walking or if she tries to run.

    Answers to Kevin's questions:
    1. I still can't figure out what I'm doing wrong in trying to find the STJ axis in NWB using your method. I have a video of me trying which I can send separately.

    2. Peroneus brevis and longus are both intact and strong.

    3. If my assessment is correct, in relaxed stance, her right foot is supinated about 20 degrees from her max pronation position (10 deg eversion) and the left foot is supinated about 12 degrees from max pronation (6 deg eversion).

    4. She is able to achieve greater pronation on right than left (10 v. 6 degrees calcaneal eversion)

    5. Supination resistance test: Able to slightly supinate right with moderate force. Unable to supinate left.

    6. The peroneal tendons do not feel tonically active and she has no tenderness to palpation over the peroneals. She is VERY tender to palpation over the distal medial third of her tibia.

    7. Her pain is definitely not over her peroneals. She points to the area indicated in the pictures (medial and lateral to achilles) and her chief area of pain to palpation is the distal third of her medial tibia. I tried placing a forefoot and rearfoot valgus wedge in her sneakers today and I am scheduled to see her again on Thursday.

    Thanks for any input!

    Ann

    P.S. My numbers are definitely not exact. With the low reliability of measurements I generally approximate being sure to at least reflect the difference right to left.



    Debra walking.png

    Max pronation test.png

    Debra RCS rear.jpg

    Debra RCS front.jpg
     
  11. Ann PT

    Ann PT Active Member

    Looks like the videos didn't work. I sent them to Kevin's email directly because I can open them on email but not on this forum. Computer skills are not my strong point! I hope he got them!

    Thanks,
    Ann
     
  12. I got the videos. We will to find a way to post them up to Podiatry Arena for others to see.:drinks
     
  13. NewsBot

    NewsBot The Admin that posts the news.

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  14. Here are the videos of Ann's patient who appears to have a more supinated right foot which appears also to be more laterally deviated at the subtalar joint axis.

    Maximum Pronation Test






    Supination Resistance Test






    Treadmill Walking Gait Video

     
    Last edited by a moderator: Sep 22, 2016
  15. Here are larger photos of Ann's patient's feet.
     
  16. Ann PT

    Ann PT Active Member

    So now having seen these pictures and video, any other thoughts about her pain around the achilles after being sedentary and pain further up her calves (indicated by the lines on her legs) with a lot of walking or any running? She doesn't appear to me to have the expected load on her peroneals. Anyone see anything that indicates differently? And even with a laterally deviated subtalar joint, I would think her body weight and gravity would force some pronation especially since her midtarsal joint is hypermobile. Thoughts?

    Thank you! (And thank you, Kevin, for posting the video and pictures for me!)
    Ann

    P.S. I still don't know the effect of the valgus wedge. She hasn't come back since I put it in her shoe.
     
  17. Ann PT

    Ann PT Active Member

    And Eric, can you explain this part again...

    "With an average STJ axis location a forward shift of the center of pressure will tend to create a pronation moment..."

    I understand the achilles supinating the foot with plantarflexion and that plantarflexion moves the COP more anterior. Where you lose me is the shift in COP causing a pronation moment...

    Thanks,
    Ann
     
  18. Lab Guy

    Lab Guy Well-Known Member

    I think what Eric is saying is that the eccentric contraction of the Soleus is shifting the COP more anterior as it is loading the forefoot on the ground. The Soleus is a strong plantarflexor and invertor as it inserts medial to the STJ axis but its supination moment is counterbalanced by the pronation moment of the GRF acting on the lateral column as the moment arm is longer to the STJ axis that is normal.

    However, your patient has a laterally deviated STJ axis so the moment arm is much shorter for the GRF to exert a pronation moment and resist the longer moment arm that the posterior tibial tendon has along with the Soleus. In this case the Peroneals must fire to help decelerate the supination moment secondary to the mechanical advantage the plantarflexors-invertors have due to their longer moment arm from the STJ axis.

    Have you done the Coleman block test? Allow the rigid right first ray to overhang on a block and the STJ will come back to verticle as it no longer has to supinate to allow the lateral forefoot to bear weight. Interesting case.

    Steven
     
  19. JonathanH

    JonathanH Member

    Hi Ann,
    Does the patient have any limb length discrepancies?
    how high is the force required to perform jack's test/Hubscher's maneuver on both feet?

    Jonathan
     
  20. efuller

    efuller MVP

    Steven, understands it. However I would use slightly different words to explain it. Draw an outline of the transverse plane plane view of the foot. Copy it. On one of them draw a STJ axis that goes from the center of the heel through the 1st metatarsal head. That one is the average STJ axis. Now take the other one and draw a STJ axis that goes from the center of the heel to the 3rd metatarsal head (Lateral axis).

    So, with any tension in the Achilles tendon, the center of pressure is shifted anteriorly. The center of pressure is the average point of force from all points of contact with the ground. The moment from ground reaction force can be calculated using the location of the center of pressure relative to the STJ axis. So, with a little bit of tension in the Achilles there will be some pressure on the heel and more pressure on the forefoot. In this situation, the center of pressure will be between the ankle joint and the metatarsal heads. As tension in the Achilles tendon is increased, eventually the heel will lift off of the ground and the center of pressure will be under the metatarsal heads (With a lot of force on the toes the center of pressure could be distal to the metatarsal heads). Let's say the center of pressure is under the 2nd metatarsal head. (Exactly where the center of pressure is will be dependent on available range of motion of the STJ and MTJ and the relative activation of the posterior tibial and peroneal muscles.)

    Now, put the center of pressure dot under the 2nd metatarsal head in your two drawings. In the average axis foot the center of pressure under the 2nd metatarsal head will cause a pronation moment and in the laterally positioned STJ axis foot the center of pressure will cause a supination moment.

    Eric
     
    Last edited: Sep 3, 2014
  21. efuller

    efuller MVP


    In the static stance video it appears that she is going from resting position to a position where the calcaneus is more everted and then relaxing back to the original position. That is essentially showing that the Coleman block test would shoe additional eversion when placed under the lateral forefoot.

    In the palpation of the axis video: Kevin, in his paper on this technique talked about putting the foot in plantar parallel position. It is important to do this because if you palpate the location in the maximally pronated position you will get a different location of the axis than if you palpate in neutral position. The foot moves around the axis, so as you move the foot, the location of the axis will stay in the same position, so there is an apparent lateral movement of the axis when you assess the position of the axis in the maximally pronated versus the neutral position of the subtalar joint. So, when you take that into account with the stance video, to get the position of the axis in stance, you should palpate the location closer to neutral as opposed to maximally pronated. You should palpate the location of the axis in the position that the STJ is in when it is in "resting" stance. You want to know what the ground is going to do in the foot in stance, not some random position of the joint.

    Your comment about laterally deviated STJ axis and mobile MTJ. It doesn't matter how mobile the MTJ is, when you, or the ground, push lateral to the axis you will be creating a pronation moment. And when you, or the ground, push medial to the axis you will be creating a supination moment.

    Eric
     
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