Editing Foot (section)

===Muscles===
The muscles acting on the foot can be classified into [[extrinsic muscles]], those originating on the anterior or posterior aspect of the lower leg, and [[intrinsic muscles]], originating on the dorsal (top) or plantar (base) aspects of the foot.

====Extrinsic====
[[File:Gray437.png|thumb|80px|Anterior leg muscles]]

All muscles originating on the lower leg except the [[popliteus muscle]] are attached to the bones of the foot. The tibia and fibula and the [[interosseous membrane of leg|interosseous membrane]] separate these muscles into anterior and posterior groups, in their turn subdivided into subgroups and layers.<ref name="Platzer-256">Platzer 2004, p. 256</ref>

=====''Anterior group''=====
''Extensor group'': the [[tibialis anterior muscle|tibialis anterior]] originates on the proximal half of the tibia and the [[interosseous membrane of leg|interosseous membrane]] and is inserted near the [[tarsometatarsal joint]] of the first digit. In the non-weight-bearing leg, the tibialis anterior dorsiflexes the foot and lift its medial edge ([[supination]]). In the weight-bearing leg, it brings the leg toward the back of the foot, like in rapid walking. The [[extensor digitorum longus muscle|extensor digitorum longus]] arises on the lateral tibial condyle and along the fibula, and is inserted on the second to fifth digits and proximally on the fifth metatarsal. The extensor digitorum longus acts similar to the tibialis anterior except that it also dorsiflexes the digits. The [[extensor hallucis longus muscle|extensor hallucis longus]] originates medially on the fibula and is inserted on the first digit. It dorsiflexes the big toe and also acts on the ankle in the unstressed leg. In the weight-bearing leg, it acts similarly to the tibialis anterior.<ref name="Platzer-258">Platzer 2004, p. 258</ref>

''Peroneal group'': the [[peroneus longus muscle|peroneus longus]] arises on the proximal aspect of the fibula and [[peroneus brevis muscle|peroneus brevis]] below it. Together, their tendons pass behind the lateral [[malleolus]]. Distally, the peroneus longus crosses the plantar side of the foot to reach its insertion on the first tarsometatarsal joint, while the peroneus brevis reaches the proximal part of the fifth metatarsal. These two muscles are the strongest pronators and aid in plantar flexion. The peroneus longus also acts like a bowstring that braces the transverse arch of the foot.<ref name="Platzer-260">Platzer 2004, p. 260</ref>

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=====''Posterior group''=====
The ''superficial layer'' of posterior leg muscles is formed by the [[triceps surae muscle|triceps surae]] and the [[plantaris muscle|plantaris]]. The triceps surae consists of the [[soleus muscle|soleus]] and the two heads of the [[gastrocnemius muscle|gastrocnemius]]. The heads of gastrocnemius arise on the [[femur]], proximal to the condyles, and the soleus arises on the proximal dorsal parts of the tibia and fibula. The tendons of these muscles merge to be inserted onto the calcaneus as the [[Achilles tendon]]. The plantaris originates on the femur proximal to the lateral head of the gastrocnemius and its long tendon is embedded medially into the Achilles tendon. The triceps surae is the primary plantar flexor. Its strength becomes most obvious during ballet dancing. It is fully activated only with the knee extended, because the gastrocnemius is shortened during flexion of the knee. During walking it not only lifts the heel, but also flexes the knee, assisted by the plantaris.<ref name="Platzer-262">Platzer 2004, p. 262</ref>

In the ''deep layer'' of posterior muscles, the [[tibialis posterior muscle|tibialis posterior]] arises proximally on the back of the [[interosseous membrane of leg|interosseous membrane]] and adjoining bones, and divides into two parts in the [[Sole (foot)|sole of the foot]] to attach to the tarsus. In the non-weight-bearing leg, it produces plantar flexion and supination, and, in the weight-bearing leg, it proximates the heel to the calf. The [[flexor hallucis longus muscle|flexor hallucis longus]] arises on the back of the fibula on the lateral side, and its relatively thick muscle belly extends distally down to the [[flexor retinaculum of foot|flexor retinaculum]] where it passes over to the medial side to stretch across the sole to the distal phalanx of the first digit. The [[popliteus muscle|popliteus]] is also part of this group, but, with its oblique course across the back of the knee, does not act on the foot.<ref name="Platzer-264">Platzer 2004, p. 264</ref>

====Intrinsic====
On the top of the foot, the tendons of [[extensor digitorum brevis muscle|extensor digitorum brevis]] and [[extensor hallucis brevis muscle|extensor hallucis brevis]] lie deep in the system of long extrinsic extensor tendons. They both arise on the calcaneus and extend into the dorsal [[aponeurosis]] of digits one to four, just beyond the penultimate joints. They act to dorsiflex the digits.<ref name="Platzer-268">Platzer 2004, p. 268</ref> Similar to the intrinsic muscles of the hand, there are three groups of muscles in the ''sole of foot'', those of the first and last digits, and a central group:

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''Muscles of the big toe'': the [[abductor hallucis muscle|abductor hallucis]] stretches medially along the border of the sole, from the calcaneus to the first digit. Below its tendon, the tendons of the long flexors pass through the [[tarsal tunnel|tarsal canal]]. The [[abductor hallucis muscle|abductor hallucis]] is an abductor and a weak flexor, and also helps maintain the arch of the foot. The [[flexor hallucis brevis muscle|flexor hallucis brevis]] arises on the medial cuneiform bone and related ligaments and tendons. An important plantar flexor, it is crucial to ballet dancing. Both these muscles are inserted with two heads proximally and distally to the first [[metatarsophalangeal joints|metatarsophalangeal joint]]. The [[adductor hallucis muscle|adductor hallucis]] is part of this group, though it originally formed a separate system (see [[contrahens]]). It has two heads, the oblique head originating obliquely across the central part of the midfoot, and the transverse head originating near the metatarsophalangeal joints of digits five to three. Both heads are inserted into the lateral [[sesamoid bone]] of the first digit. The adductor hallucis acts as a tensor of the plantar arches and also adducts the big toe and might plantar flex the proximal phalanx.<ref name="Platzer-270">Platzer 2004, pp. 270–72</ref>

''Muscles of the [[fifth toe|little toe]]'': Stretching laterally from the calcaneus to the proximal phalanx of the fifth digit, the [[abductor digiti minimi muscle (foot)|abductor digiti minimi]] form the lateral margin of the foot and are the largest of the muscles of the fifth digit. Arising from the base of the fifth metatarsal, the [[flexor digiti minimi brevis muscle (foot)|flexor digiti minimi]] is inserted together with abductor on the first phalanx. Often absent, the [[opponens digiti minimi muscle|opponens digiti minimi]] originates near the cuboid bone and is inserted on the fifth metatarsal bone. These three muscles act to support the arch of the foot and to plantar flex the fifth digit.<ref name="Platzer-272">Platzer 2004, p. 272</ref>

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''Central muscle group'': The four [[lumbricals of the foot|lumbricals]] arise on the medial side of the tendons of [[flexor digitorum longus muscle|flexor digitorum longus]] and are inserted on the medial margins of the proximal phalanges. The [[quadratus plantae muscle|quadratus plantae]] originates with two slips from the lateral and medial margins of the calcaneus and inserts into the lateral margin of the flexor digitorum tendon. It is also known as the flexor accessorius. The [[flexor digitorum brevis muscle|flexor digitorum brevis]] arises inferiorly on the calcaneus and its three tendons are inserted into the middle phalanges of digits two to four (sometimes also the fifth digit). These tendons divide before their insertions and the tendons of flexor digitorum longus pass through these divisions. Flexor digitorum brevis flexes the middle phalanges. It is occasionally absent. Between the toes, the [[dorsal interossei of the foot|dorsal]] and [[plantar interossei muscles|plantar interossei]] stretch from the metatarsals to the proximal phalanges of digits two to five. The plantar interossei adduct and the dorsal interossei abduct these digits, and are also plantar flexors at the metatarsophalangeal joints.<ref name="Platzer-274">Platzer 2004, p. 274</ref>