Muscular System: Muscles of the Leg and Foot

muscles of the leg

-allow for movements at the ankle (DF/PF), subtalar joint (eversion/inversion), toes (flex/ext at MTP, IP joints)

-3 muscle compartments: anterior, lateral, posterior

-crural fascia = deep fascia of the leg

-tendons held in place by retinacula: extensor (anterior compartment, superior and inferior), fibular (by lateral malleolus, superior and inferior), flexor (by medial malleolus)

anterior (extensor) compartment

dorsiflexion and toe extension

-tibialis anterior, extensor digitorum longus, extensor hallucis longus, fibularis tertius

-deep fibular nerve

lateral compartment

eversion and plantar flexion

-fibularis longus, fibularis brevis

-superficial fibular nerve

posterior (flexor) compartment

plantar flexion and toe flexors

-gastrocnemius, soleus, plantaris, flexor hallucis longus, tibialis posterior, flexor digitorum longus

-tibial nerve

sciatic nerve

branches to:

-tibial (posterior compartment of thigh and leg)

-common fibular (short head of biceps femoris) branches to: deep fibular nerve (anterior compartment of leg), superficial fibular nerve (lateral compartment of leg)

tibialis anterior

-origin: lateral condyle and proximal 2/3 of tibia, interosseous membrane

-insertion: medial and inferior surface of medial cuneiform and metatarsal 1

-action: DF, inversion, supports medial longitudinal arch

-innervation: deep fibular nerve L4-L5

extensor digitorum longus

-origin: lateral condyle, proximal 3/4 of fibula, interosseous membrane

-insertion: middle and distal phalanges of toes 2-5 via extensor expansion

-action: DF, inversion, extension of toes 2-5 at MTP, DIP, PIP

-innervation: deep fibular nerve L4-L5

fibularis tertius

continuous with EDL

-origin: distal anterior fibula, interosseous membrane

-insertion: dorsum of 5th metatarsal

-action: DF, eversion

-innervation: deep fibular nerve L4-L5

extensor hallucis longus

-origin: distal 1/3 of anterior fibula, interosseous membrane

-insertion: distal phalanx of great toe

-action: extension of great toe MTP, IP, DF, inversion

-innervation: deep fibular nerve L4-L5

fibularis longus

-origin: head and proximal 2/3 of lateral fibula

-insertion: tendon curves under foot to metatarsal 1 and medial cuneiform

-action: support medial + lateral longitudinal arch, transverse arch, lateral ankle stability, PF, eversion

-innervation: superficial fibular nerve L5-S2

fibularis brevis

-origin: distal 2/3 of lateral fibula

-insertion: tendon runs behind lateral malleolus to base of 5th metatarsal

-action: supports lateral longitudinal arch, lateral ankle stability, PF, eversion

-innervation: superficial fibular nerve L5-S2

gastrocnemius

-origin: medial head- posterior femur, above medial condyle, lateral head- lateral condyle of femur

-insertion: posterior calcaneus via calcaneal tendon

-action: PF in knee extension, knee flexion

-innervation: tibial nerve S1-S2

soleus

-origin: posterior aspect of superior tibia and fibula, head of fibula, interosseous membrane

-insertion: posterior calcaneus via calcaneal tendon

-action: PF (PM)

-innervation: tibial nerve S1-S2

plantaris

-origin: posterior femur, superior to lateral condyle

-insertion: posterior calcaneus (next to calcaneal tendon)

-action: PF, knee flexion (weak), proprioceptor

-innervation: tibial nerve S1-S2

popliteus

acts at knee to unlock in terminal extension

-origin: lateral condyle of femur and lateral meniscus

-insertion: proximal posterior tibia

-action: knee flexion with medial tibial rotation (open chain), knee flexion with lateral rotation of femur (closed chain)

-innervation: tibial nerve L4-S1

tibialis posterior

deepest of posterior compartment and 1st at MM

-origin: posterior tibia and fibula, interosseous membrane

-insertion: navicular, cuneiforms, cuboid, and base of metatarsals 2-4

-action: PF, inversion (PM), supports medial longitudinal and transverse arch

-innervation: tibial nerve S2-S3

flexor digitorum longus

most medial of posterior compartment, 2nd at MM

-origin: medial part of posterior tibia

-insertion: tendon splits to distal phalanges of toes 2-5

-action: PF, flex toes 2-5 at MTP, PIP, DIP, inversion, supports lateral + medial longitudinal arch, transverse arch

-innervation: tibial nerve S2-S3

flexor hallucis longus

most lateral and largest of posterior compartment, 3rd at MM

-origin: distal 2/3 of posterior fibula, interosseous membrane

-insertion: tendon runs under foot to base of distal phalanx of great toe

-action: PF, flex great toe at MTP, IP, inversion, supports medial longitudinal arch

-innervation: tibial nerve S2-S3

intrinsic muscles of the foot

perform movements of the toes

-dorsum of the foot: extensor hallucis brevis, extensor digitorum brevis

-plantar surface of the foot: plantar aponeurosis (thickening of plantar fascia), 4 layers of muscle with the 1st layer including flexor digitorum brevis

extensor hallucis brevis

-origin: anterior calcaneus and extensor retinaculum

-insertion: base of proximal phalanx of great toe

-action: extend great toe at MTP

-innervation: deep fibular nerve L5-S1

extensor digitorum brevis

-origin: anterior calcaneus and extensor retinaculum

-insertion: extensor expansion of toes 2-4

-action: extend toes 2-4 at MTP, PIP, DIP

-innervation: deep fibular nerve L5-S1

flexor digitorum brevis

-origin: calcaneal tuberosity

-insertion: middle phalanx of toes 2-5

-action: flex toes 2-5 at MTP, PIP

-innervation: medial plantar nerve (branch of tibial nerve) S2-S3