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Sacro-iliac jt/ piriformis and low gear toe-off

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Pod on sea, Nov 24, 2010.

  1. Pod on sea

    Pod on sea Active Member

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    Thanks to Craig Payne for the excellent bootcamp. He mentioned low-gear toe-off causes SI joint and I think he said piriformis issues. Can Craig/anyone explain fully?
  2. Griff

    Griff Moderator

  3. Craig Payne

    Craig Payne Moderator

    What I suggested was that if Bojon Mollor's low gear/oblique axis propulison is present, then it is harder for the body to transfer weight from one foot to the other in gait and that this is cause the SI/pelivc region to function "differently" or "harder", especially if the low gear propulsion is assymmetrical and there is some resultin assymentrical motion proximally.

    Whether this is sufficent enough to cause problems is not something I would definitivly say (others would).

    I can, however, cite a number of n=1's which did present with pain in that region, had a low gear propulsion and when it was fixed, they got better.
  4. Pod on sea

    Pod on sea Active Member

    Great,many thanks. So in your experience do the issues occur on the same side or the contralateral side?
  5. Craig Payne

    Craig Payne Moderator

    Can't say I have noticed any pattern yet, but also can't say I have been exactly looking for it either ... good research project for someone to take on.
  6. Why??
  7. Pod on sea

    Pod on sea Active Member

    Has it been shown that if our centre of mass is moving laterally when it should be moving medially it can cause pain/strain in the SI jts?
    If so, would it also have implications in piriformis syndrome or other glute/lat hip muscular pathology?
    ..or if you have a tight or overactive piriformis does that lead to a more lateral/abductory twist at toe-off?

    Ahh Craig, see what you've done..questions,questions!
  8. Graham

    Graham RIP

    Perhaps because there may be a greater abductory twist to allow the COP to move medially from the lateral direction created by the low gear position?
  9. efuller

    efuller MVP

    Winter showed that weight shift was a fairly normal process that can be explained by location of center of mass and location of center of pressure in the frontal plane. In gait you have the line of progression. As you walk toward an object your average position of center of mass will oscilate around the "line of progression." The placement of the feet will be further away from the line of progression than the oscillation of the center of mass. So as you are on one foot, your center of mass is medial to the center of pressure so this creates a moment for you to fall toward your other foot. The farther the distance from the center of mass to the center of pressure, the bigger the moment, the faster you will accelerate toward the other foot. (Think of a tennis player awaiting a serve. They stand with their feet far apart so that when they lift one foot up they will fall faster in the direction that they want to go.)

    So, with high gear push off, the center of pressure is more medial and with high gear push off the center of pressure will be more lateral. So, with foot placement being the same, you should fall faster toward the opposite foot with low gear push off.

    One of the things that I was taught when I was a student was that with orthotics you may see a narrower base of gait, so this may not be a constant.

    So, the above explanation is not a good one. That doesn't mean that piriformis can't get better for some other reason when you change the push off.

  10. Eric, I agree. Hence my "why?" question. Only one point: you said high gear push off twice: "So, with high gear push off, the center of pressure is more medial and with high gear push off the center of pressure will be more lateral."
  11. efuller

    efuller MVP

    Thanks, Simon. the second high should be low.

    with high gear push off, the center of pressure will be more medial with low gear push off the center of pressure will be more lateral.
  12. How might angle of gait, i.e. foot placement influence this? For example: in-toe; Manchester style (very broad out-toe)?
  13. Graham

    Graham RIP


    I would think that an in-toed gait may require a greater abductory twist to move the COP medially perhaps transferring a rotational force more proximally greater than that of an abducted gait...perhaps.
  14. Why does the centre of pressure need to move medially?
  15. Graham

    Graham RIP

    So that weight can be transferred and assumed to the swing leg at heel contact?
  16. The assumption being that weight cannot be transferred if the centre of pressure is moving laterally? OK. Why can't the weight be transferred to the contacting limb if the centre of pressure is moving laterally under the propulsive limb? Centre of pressure represents only the point of application of the net ground reaction force (GRF), it does not define the direction nor magnitude of the net GRF vector. The CoP can move in what ever direction you like, so long as the GRF vector is pointing in the right direction.

    Further: the centre of pressure will move medially as the foot pronates, the centre of pressure with move laterally as the foot supinates.
  17. Graham

    Graham RIP

    Just tried that. It can, but I'm not sure it is ideal! The nature of the forces projected proximally would depend on the manner in which an individual dealt with this situation. If you in-toe and roll through low gear without an abductory twist there is less rotation proximally than if you abductory twist at propulsion. Whether there is a rotational influence on the SI jnt resulting in pathology I don't know!
  18. I love the concepts of ideal ;) :drinks
  19. Dananberg

    Dananberg Active Member

    I think that the relationship between SIJ dysfunction and low gear pushoff is being mistated. By that I mean that they are both results of a similar mechanical effect.

    Low gear push off can also be thought of simply as lateral weight bearing. This is often related to fibula restriction and secondary peroneal inhibition. It is a relatively common occurrance. However, since the biceps femoris inserts into the the fibula head, and proximally, connects to the sacrotuberous ligament, there is a direct connection between the fibula, sacrum and SIJ.

    SIJ functions in two basic positions, nutated and counternutated. Nutated is a forward rotation of the superior aspect of the sacrum, and counternutation is conversely a rearward (retrograde) rotation. For the sacrum to switch from the counter to nutated position, the biceps tendon must be allowed to have the tension relieved, and this is accomplished via fibula translation.

    Should the fibula be fixed, then the SIJ motion can be negatively impacted, and, coincidentally, the peroneals are functioning in an inhibited state. By manipulating the fibula and permitting normal translation, peroneal strength and sacral motions can be restored. I have actually seen this happen many, many times and have seen immediate improvement in both back symptoms and excessive lateral weight bearing.


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