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Energy return in medial ankle ligaments

Discussion in 'Biomechanics, Sports and Foot orthoses' started by David Smith, Jun 4, 2011.

  1. David Smith

    David Smith Well-Known Member

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    Dear All

    I have a young male sprinter 17yrs old who complains that his right arm goes numb and feels disconnected when sprinting, this occurs after a couple of 60meter sprints. He also experiences a similar feeling in the right upper lateral leg but this is after a lot of training. He also reports mild lateral right knee and hip pain when sprint training. He was referred by his GP to physio who didn't know what it was and referred to me thinking it may be due to poor shock attenuation due to his 'flat feet'. However this seems unlikely to me since when sprinting he is a forefoot striker and uses a lot of knee flexion extension in propulsion. At low medium speeds and walking he changes to heel strike. On the treadmill video pics he is running fast enough to get onto toes. Watching him run outside his vertical CoM displacement becomes less the faster he runs and greatest at medium speeds with heel strike.

    My feeling was this was a neurological problem perhaps down to two possibilities:
    1) Nerve in the brachial plexus being compressed by muscle tension because of high arm / hunched shoulder posture during sprinting. (doesn't explain leg neuropathy)

    2) Problem of restriction of blood supply to CNS possibly at the brain and through the Circles of Willis. (This might also explain leg problem)

    Speaking to the physio I usually ref to he thought the most likely cause was tightness in the trapezium due to arm and shoulder posture. I referred to Him and wrote to GP outlining my concerns.

    Any thought on that would be appreciated.

    I am still making him orthoses to help with running in terms of the lateral knee pain and hip pain, which may be from lateral knee compartment compression since it is likely from his assessment that there are high abduction moments at the knee from GRF and CoP on the lateral foot. The large pronation RoM through the forefoot is tending to internally rotate the knee and this results in high tension in the ITB as it resists this. I was thinking of a high arched flexible orthosis with forefoot medial posting, EVA neutral post in the rearfoot and 4mm heel lift.

    You can see from the attached pics that the CoP on the right foot is mostly lateral and the velocity increase significantly in midstance.
    From the Video pics - At forefoot strike the foot and STJ is extremely inverted and at late midstance the rearfoot is still inverted but the forefoot goes through a large range of pronation and the medial ankle ligaments and retinaculum are under high tension ( shown by red arrow). The medial arch is almost completely flattened at this point. The left foot is similar and fromthe pressure mat data appears to bend at the midfoot during midstance i.e. the pressure increases on the lateral midfoot as the heel pressure reduces.

    My question would be this: If I were to use the orthotic prescription described, would this reduce tension in the medial ankle ligaments (and probably the spring ligament) and so reduce the amount of stored energy available for propulsion? Or would this be compensated somewhat by the energy stored in the orthosis medial arch during its deflection.

    By reducing the functional RoM of the forefoot and allowing the heel to contact the ground for longer and with possibly with more force, would this be reducing the potential of stored elastic energy and so reduce sprinting maximum speed?

    The paradox may be that, I would imagine, this person would like to stop injury occurring and injury potential but at the same time maintain maximum effort potential (in terms of muscle and ligament forces) in order to gain maximum sprint speeds.





    This pic shows vertical CoM excursion

    What would you say here please?

    Cheers and Regards Dave
  2. efuller

    efuller MVP

    I'd want an answer to what why his arm going numb before I'd go to far with the foot orthosis. The explanation of shock attenuation is not very good. That's a little out of my scope of practice, but I would want another opinion on the arm numbness. Or, at least be satisfied that he was making the numbness up. CT of upper spine??

    You are mentioning two possible location for the medial knee pain. I'd pick on or the other and I would go with the compression laterally from abduction from lateral cop at contact. The ITB is stressed with frontal plane movement/ moments and not so much with transverse motions seen with STJ pronation, so I think that it is less likely. Where is the knee pain on physical exam. Does an abudction moment applied to the lower leg reproduce the pain at the knee?

    If by medial forefoot posting you mean a varus wedge under the metatarsals then I would agree. The purpose would be to decrease the location of lateral loading at contact in this forefoot striker.

    Looking at the individual frames of the pressure map, does the medial forefoot load very late? From the pictures it appears that you are dealing with the partially compensated varus foot with very high lateral loads and stresses.

    I really doubt there is much energy returned from medial ankle ligament stretching. Power is equal to moment x angular velocity. As soon as you have movement away from the end of range of motion the force in the ligaments will decrease rapidly and you would be needing a moment from some other source to produce power.

    I don't understand which modification is going to allow the heel contact the ground longer. What structures are you thinking provide the elastic energy?

  3. David Smith

    David Smith Well-Known Member

    Thanks for your reply regards Dave
  4. Dave:

    You may consider thoracic outlet syndrome as a cause of his arm numbness while running. Not very common, but it does happen.

    Attached Files:

  5. RobinP

    RobinP Well-Known Member

    Vitamin B12 deficiency? The exercise induced onset would suggest this might not be the case but might be worth checking out?

    Also, I saw a patient a couple of years back who turned out to have functional kinking of the arteries.

    This paper is obviously directed at lower limb issues and although brachial artery kninking is possible, my reading would suggest that it mainly occurs as a result of trauma(recent or historical)

    Good luck

  6. David Smith

    David Smith Well-Known Member

    Yes that's just the kind of pathology we were thinking of. Very useful.

    Cheers Kevin
  7. Dave back in the day I was a 400m runner- was in an elite squad. We had 1 of our squad who left arm used to go numb and cramp. It was stressed induced, both physical and mental.

    At the end of sessions or big races the arm would stop moving go numb etc but if we said relax it seemed to break the change in his left arm - he had test after test with no answer besides nerve related.

    600 m at race pace used was always a trigger.
  8. Ben

    Ben Member

    Before rush into orthoses based on the barefoot pics, need to remember that when sprinting he will be in spikes that have a varus configuration to the forefoot anyway, and with the pitch of the shoe these pictures will look very different.
    In regards to leg neuropathy, thought FAI? Whats hip ROM like? Especially R leg running the bends on the track.
    Otherwise ITB probably big contributor.
  9. David Smith

    David Smith Well-Known Member

    Good point Ben, I didn't know that all running spikes had a varus construction. I did watch him running in his training shoes, which is what he uses for everyday sprint training the picture was quite similar. I did also advise that when he uses spikes the orthoses will not be suitable for those for various reasons but mainly because of the narrow last and low volume. His hip RoMs in all degrees of freedom are fine.

    Many thanks Dave

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