Role of the Ankle and Subtalar Joint in Gait

- See:
      - Ankle Joint: Anatomy
      - Equinus Contracture
      - Gait (discussion of)
      - Sub-Talar Joint

- Diagram:

- Ankle Joint: During Gait:
    - ankle joint has an oblique axis;
    - in frontal plane, ankle joint is angled 82 deg, directed laterally;
    - in transverse plane, axis is directly laterally & posteriorly about 20-30 deg;
    - as a consequence of this oblique ankle axis is that foot  externally rotates when the ankle is in maximal dorsiflexion;
          - when the foot plantar flexes, it internally rotates;
    - w/ foot fixed on ground as in stance phase of gait;
          - forward tibial progression (ankle dorsiflexion) results in tibial internal rotation;
          - when tibia is behind foot (ankle plantar flexion), it is externally rotated;

- Subtalar Joint During Gait:
    - external rotation of leg produces supination of the foot;
        - during wt bearing, external rotation of limb & subsequent forefoot supination are followed by pronation twist of forefoot to remain plantigrade;
        - this tends to lock the foot, making it a rigid lever;
    - internal rotation of the leg produces a pronated foot;
        - internal rotation of leg & its subsequent pronation are followed by supinatory twist of the forefoot to remain plantigrade;
        - this mechanism unlocks midtarsal joint & produces mobile midfoot noted at time of heel contact & first 15% of the gait cycle;
    - inversion of the heel in the normal foot promptly occurs as wt is transferred from heel to forefoot when a person rises on the toes;
         - such inversion of the heel causes the mid foot to covert from a mobile structure to a rigid lever;
    - when the heel is elevated during standing or at the time of push off, wt of the body is shared by all the metatarsal heads;
          - to achieve this fair division of the body wt among the metatarsals, foot must supinate slightly and deviate laterally;

- Ankle Joint and Subtalar Joint Work Together:
    - ankle combines dorsiflexion with abduction and plantar flexion w/ adduction, subtalar joint combines dorsiflexion, abduction, & eversion in one direction and plantar flexion, adduction, and inversion in the other direction;
         - these combined subtalar motions are referred to as pronation & supination;
    - when the subtalar joint is fused, rotation is increased in the ankle and may cause arthritic change;
         - when the ankle is fused, greater stresses are placed on the sub-talar and midtarsal joints;
    - dorsiflexion of the toes tightends the plantar aponeurosis and assists in inversion of the heel;
         - supinatory twist activates the locking mechanism in foot, thus converting a flexible foot into a rigid lever, an action that is necessary at push off

Ankle and subtalar kinematics measured with intracortical pins during the stance phase of walking.

The jargon of pedal movements.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Thursday, September 20, 2012 6:59 pm