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STJ motion

Discussion in 'Biomechanics, Sports and Foot orthoses' started by RFVarus6, Oct 18, 2017.

  1. RFVarus6

    RFVarus6 Welcome New Poster


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    Hello All,

    I was wondering if there is any research or information about motion that occurs across the each individual facet of the STJ. For example, how much motion would occur across the posterior vs the anterior vs the middle, or is it all equal?

    Then to follow that up, would a deviation of the axis change the motion across these joints?
     
  2. efuller

    efuller MVP

    A good resource is
    A kinematical analysis of the tarsal joints. An X-ray photogrammetric study.
    van Langelaan EJ.
    Acta Orthop Scand Suppl. 1983;204:1-269.

    The above can give you a good idea where the axis lies relative to the individual bones. An interesting thing about the facets is that each bone has a concave and a convex surface. (if you count the middle and ant facet of the calcaneus as a single facet as it sometimes is anyway.) A way to understand how a single axis of a joint could have both a convex and concave surface is to imagine two cones pointing toward each other around the joint axis. (Most of the time people thing of joint surfaces as being the surface of a cylinder and not a cone.) If the axis is going from your left to your right the joint surfaces of the left cone could be on top of the cone and the joint surfaces on the right cone could be on the bottom of the cone. This makes sense as you look at the posterior facet as the radius of curvature of the facet is smaller closer to the sinus tarsi and larger farther from the sinus tarsi. The posterior facet looks like it was cut out from the surface of a cone.

    So to answer your question if you selected a point on the joint surface farther from the axis that point would move farther, relative to the opposing surface, than a point that was closer to the axis. This is true for the individual joint facets.

    It is an interesting question as to whether axis deviation would affect the motion on the joints. It is also an interesting question on how the joint surfaces would look different for different axis positions.
     
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