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Understanding plantar flexion

Discussion in 'Biomechanics, Sports and Foot orthoses' started by seladore, May 7, 2013.

  1. seladore

    seladore Welcome New Poster

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    Hi everyone,

    I hope this isn't too basic a question. I'm trying to understand the muscles and movements involved in plantar flexion, and google results are proving to be contradictory and confusing.

    Can anyone help and talk me through the muscles and movements involved?

    Thanks in advance.
  2. Craig Payne

    Craig Payne Moderator

    All the muscles that have a tendon that passes posteriorly to the ankle joint axis provide a plantarflexion moment.

    What are you using Google for? Check the anatomy textbooks!
  3. efuller

    efuller MVP

    When the gastroc soleus muscles shorten, a force from inferior to superior is applied to the calcaneus and The insertion of the Achilles. This force would tend to accelerate the calcaneus up. The talus and tibia are in the way of this upward acceleration. (The origin of the gastroc and soleus muscles are applying a downward force simultaneously to the tibia.) When a downward force is applied to the top of the talus and an upward force is applied the Achilles insertion on the calcaneus a force couple is created. This force couple will create a plantar flexion moment on the foot. The ligaments and joint surfaces of the ankle joint are shaped so that the motion that occurs is easiest at that ankle joint (as opposed to the subtalar joint) and the ankle will plantar flex if the opposing moments are smaller.

    Is that more than you wanted?

  4. drsha

    drsha Banned


    1. Could you give us a diagram or point us to one that illustrates this plantarflexion moment?

    2. How does the moment created by Peroneus Longus affect this equilibrium?

  5. Rob Kidd

    Rob Kidd Well-Known Member

    Do not underestimate fibularis longus; it forms a sling around the apex of the long arch together with Tib. Ant. We should note the manner in which this and other major muscles inserting into the foot "span" joints, thus reducing mobility. Sadly, sometimes, we walk away from the obvious. Yes, I guess it does have a plantarflexon moment, but I respectfully suggest that this is a minor part of this muscles's function.
  6. efuller

    efuller MVP

    The moment, at the ankle joint, from peroneus longus is very small because the tendon passes very close to the ankle joint axis.
  7. efuller

    efuller MVP

    The files of my drawings are apparently not a valid file type. It should not be that hard to visualize. Draw a foot in the sagittal view. Draw an arrow pointing downward on the talar dome and then draw an upward arrow at the attachment of the Achilles tendon.


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