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  • Foot Anatomy and Biomechanics
    Tibialis Posterior, Peroneus Longus, Peroneus Brevis and Tibialis Anterior

    A basic foot exercise involves rolling the shins out and pressing down through the outer edge of the foot while also pressing down through the inner edge of the forefoot (and optionally creating an upward pull on the center of the outer arch of the foot).

    Side view of fibula and tibia and foot showing peroneus longus and tibialis anterior muscles as well as the bottom end of the IT band. Neil Keleher. Sensational Yoga Poses.

    The foot muscles involved in this foot exercise include:

    i Tibialis Posterior

    The primary action of rolling the shins out while standing is caused by Tibialis Posterior.

    Note that rolling the shins externally can also be caused by the muscles that act on the IT Band.

    However, if the focus is on "using the feet" to roll the shins out, then this action can be driven by activation of the Tibialis Posterior.

    You may feel tension in the back of your lower leg while rolling your shins out. That could be your tibialis posterior activating.

    Tibialis Posterior Connections

    Tibialis Posterior attaches to the back surfaces of both the fibula and tibia. Its tendon passes down the inside of the ankle to attach to the underside of the inner arch of the foot.

    Tibia and fibula side view along with bones of the foot and the two muscles Tibialis Posterior and Tibialis Anterior. Neil Keleher. Sensational Yoga Poses.

    i Peroneus Longus

    Peroneus longus attaches to the outside of the fibula (the outermost and smallest of the two lower leg bones.)

    Side view of fibula and tibia and foot showing peroneus longus and tibialis anterior muscles as well as the bottom end of the IT band. Neil Keleher. Sensational Yoga Poses.

    It passes down the outside of the ankle behind the Lateral Malleolus (the bottom most part of the fibula, that sticks out of the outside of the ankle) and passes under the foot to attach to the inner arch and to the "root" of the big toe.

    The Tibialis Posterior and Peroneus Longus Working Together to Stabilize the Heel

    Because it passes behind and under the trochlear process (peroneal tubercle) on the outside of the calcaneus, Peroneus Longus tends to create a forwards push on the outside edge of the calcaneus which, unresisted, would cause the heel bone to roll inwards. This inward roll of the heel can be countered by an active Tibialis posterior since this muscle has a tendon branch that attaches to the sustentaculum tali on the inside edge of the calcaneus.

    Creating Rotational Stability via Co-activation of the Tibialis Posterior and The Peroneus Longus

    Where activation of the tibialias posterior tends to create external rotation of the shin (or a resistance to internal rotation), activation of the peroneus longus (and/or peroneus brevis) can tend to create internal rotation of the shin (or a resistance to external rotation.

    Activating together, these two muscles can work against each other to stabilize the shin against rotation while standing.

    This can be important for muscles that act on the IT Band as well as the Sartorius, Gracilis and Semitendinosus muscles since these muscles can act from the pelvis to rotate the shin outwards or inwards. With the shin stabilized against rotation by the Tibialis Posterior and Peroneus Longus, these muscles have a stable foundation from which to help control the pelvis.

    i Peroneus Brevis

    Peroneus Brevis, like Peroneus Longus, attaches outside of the fibula.

    Side view of fibula and tibia and foot showing peroneus brevis and tibialis anterior muscles as well as the bottom end of the IT band. Neil Keleher. Sensational Yoga Poses.

    It attaches to the lower part of the fibula underneath the peroneus longus.

    Activation of the peroneus longus can create a forwards push along the outside of the calcaneus. Meanwhile the peroneus brevis creates a rearwards pull on the outer-most metatarsal.

    These opposing actions can work together to help lift the center of the outer arch of the foot.

    i Tibialis Anterior

    Tibialis Anterior is situated at the front of the shin.

    Medial (inside) view of and tibia (and fibula) and foot showing tibialis anterior muscle. Neil Keleher. Sensational Yoga Poses.

    Medial/Inside View

    Lateral (outside) view of fibula and tibia and foot showing tibialis anterior muscle. Neil Keleher. Sensational Yoga Poses.

    Lateral/Outside View

    It attaches to the front of the tibia outside of the tibia, starting high up, where the bone swells to form the bottom of the knee. It passes under the extensor retinaculum, a band of connective tissue at the front of the ankle. From there it runs along the inside edge of the upper surface of the foot to attach to the top surface of the inner most cuneiform and the rearmost part of the top surface of the innermost metatarsal.

    Tibialis Anterior as a Fascial Anchor for the IT Band

    From Thomas Meyers Anatomy Trains we know that the Tibialis anterior has a connective tissue connection to the front fibers of the IT band.

    (The rear edge of the IT band has connective tissue connections to the Peroneus Longus).

    Tension in the Tibialis anterior (and/or the Peroneus Longus) can act as an anchoring mechanism for the IT band so that it it turn can act as an anchor for the Tensor Fascia Latae and/or the Gluteus Maximus.

    For myself, on one occasion where I had knee pain pretty much at the spot where the IT band connects to the Tibia, Tibialis Anterior activation helped to alleviate that knee pain.

    This sort of muscle activation, activating muscles in the same "anatomy train" is another way of creating stability. Possible names for this mechanism are "Fascial Stability" or "Fascial Anchoring" or to be clearer, "Muscle Activated Connective Tissue Anchoring."

    It's basically a means of taking up slack.

    It creates stability for a muscle by adding tension to the connective tissue structure that it is a part of.

    Stabilizing the Foot and Shin

    The actions of all of these muscles, acting in concert, can not only help shape and stabilize the arches of the foot, they also help to stabilize the shins against rotation giving muscles like the tensor fascia latae, gluteus maximus, sartorius, gracilis and semitendinous a stable foundation from which to control or help stabilize the pelvis.

    The muscles can activate to stabilize the foot with the arches nicely formed, but they can also activate to stabilize the foot, ankle and shin with the arches "collapsed", or any position in between.