The primary muscles that support the arch of the foot are the tibialis posterior and the fibularis longus (also known as peroneus longus).
Muscles Supporting the Arches of the Foot
While the intrinsic foot muscles contribute to arch support, the major muscular support comes from extrinsic muscles (originating outside the foot) and plantar fascia. The arch system can be divided into longitudinal and transverse arches.
Longitudinal Arch Support
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Tibialis Posterior: This muscle is crucial for supporting the medial longitudinal arch. It originates in the posterior compartment of the lower leg and inserts onto several tarsal bones, including the navicular, cuneiforms, and cuboid. Its primary action is to invert the foot and plantarflex the ankle, helping to maintain the arch's height. Weakness or dysfunction of this muscle can lead to flatfoot.
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Fibularis Longus (Peroneus Longus): This muscle originates on the lateral side of the leg and its tendon runs behind the lateral malleolus, across the sole of the foot, and inserts onto the base of the first metatarsal and medial cuneiform. It helps to plantarflex and evert the foot, providing dynamic support to the lateral longitudinal arch and contributing to the transverse arch.
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Flexor Hallucis Longus and Flexor Digitorum Longus: These muscles, while primarily responsible for flexing the toes, also contribute to arch support, especially during activities that require toe gripping or pushing off.
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Intrinsic Foot Muscles: The intrinsic muscles (muscles that both originate and insert within the foot) provide local support to the arches. Examples include the abductor hallucis, flexor digitorum brevis, and quadratus plantae.
Transverse Arch Support
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Fibularis Longus (Peroneus Longus): As mentioned above, the tendon of the fibularis longus runs across the plantar surface of the foot, providing dynamic support to the transverse arch.
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Tibialis Posterior: This also helps in supporting the transverse arch.
It's important to note that the plantar fascia, a thick band of connective tissue on the sole of the foot, also plays a significant role in maintaining the arches. It acts as a passive support structure, preventing the arches from flattening excessively.
