There are more than 30 muscles that attach to or affect the foot. They provide strength and stability, giving the foot its shape, keeping the bones in the proper position and providing energy to propel the foot and help it move. There are four plantar (sole) muscles layers. The first layer includes the adductor hallucis, the flexor digitorum brevis, and the abductor digiti minimi. The second layer includes the lumbricals, the third layer is made up of the flexor hallucis brevis, the adductor hallucis, and the flexor digiti minimi brevis, and the fourth layer is made of the interossei muscles.
There are four dorsal interossei muscles, which are located between the metatarsal bones. Each muscle is bipenniform, meaning it has two places where it attaches. There are also three plantar interossei muscles that are found beneath the metatarsal bones. These muscles have one point of attachment.
The extensor muscles, including the extensor digitorum brevis, the extensor digitorum longus, and the extensor hallucis longus help to raise or extend the toes to assist in the movement needed to step forward. The flexor muscles, including the flexor digiti minimi brevis, the flexor digitorum brevis, the flexor hallucis brevis, and the flexor hallucis longus help flex or bend the toes.
Other muscles that act within the foot include the peroneous brevis, which is located on the outside of the lower leg and travels from the fibula to the metatarsal bone of the little toe; the peroneus tertius, which is located against the peroneus brevis, and the peroneus longus which originates at the fibula and descends to the calcaneus, and inserts at the base of the metatarsal of the big toe.
The major muscles of the ankle include the gastrocnemius and soleus (calf) muscles, which push the foot down and allow us to go up on our toes. These two large muscles join at the ankle at the calcaneus or heel to form the Achilles tendon. The foot also serves as the attachment for the tibialis anterior, and the tibialis posterior.
A tendon is part of the muscle that attaches muscle to bone. Tendons are strong, fibrous tissues that are responsible for transferring the forces generated by the muscle to the bone, thus producing movement at the joint. When a tendon becomes irritated or inflamed it becomes painful, especially with movement. Inflammation of the tendon is called tendonitis.
The Achilles tendon is another important structure in the foot and ankle that makes it possible to run, walk, and jump. The Achilles tendon attaches the calf muscles, through the ankle joint, to the calcaenous (heel bone.) The anterior tibial tendon and the posterior tibial tendon also help support and move the foot.