MSK TBL 17: Leg & Foot - Muscles, Ligaments, Tendons, & Arches of Foot

tibialis anterior

• origin

  • lateral condyle & superior 2/3 of later surface of tibia; interosseous membrane

• insertion

  • medial cuneiform & base of 1st metatarsal

• innervation

  • deep fibular [peroneal] nerve [L4, L5]

• action

  • dorsiflexion of ankle

  • inversion of foot [w/ tibialis posterior]

  • stabilizes medial arch during walking

fibularis longus

• origin

  • head & superior 2/3 of lateral surface of fibula

• insertion

  • base of 1st metatarsal & medial cuneiform [after passing under foot]

• innervation

  • superficial fibular nerve [L5,S1,S2]

• action

  • everts foot

  • weakly assists plantarflexion

  • helps maintain transverse arch of foot

tibialis posterior

• origin

  • posterior tibia, fibula, & interosseous membrane

• insertion

  • tuberosity of navicular, cuneiforms, cuboid, & bases of metatarsals 2-4

• innervation

  • tibial nerve [L4,L5]

• action

  • inverts & weakly plantarflexes foot

  • main supporter of medial longitudinal arch

medial tibial stress syndrome

“shin splints”

• strain/microtrauma to tibia

weakness in tibialis anterior →

foot slap gait

tight footwear →

tenosynovitis of extensor digitorum longus

Jones fracture

involves 5th metatarsal bone

*fibularis tertius inserts here

*fibularis brevis also inserts here; violent contraction of the muscle → avulsion fracture on 5th metatarsal

weakness in extensor hallucis longus suggests

issue w/ L5 nerve root

damage to superior fibular retinaculum →

allows peroneal tendons to dislocate over lateral malleolus

peroneal subluxation

painful, snapping sensation of fibularis muscles

common in skiers & sprinters [forceful dorsiflexion]

muscle that is the primary site of DVTs

soleus b/c it contains a dense venous plexus

achilles reflex tests which spinal nerves?

S1-S2

flexor hallucis longus [FHL] tenosynovitis

“dancer’s tendinitis”

tendon of FHL can rupture in dancers or atheletes due to constant friction

painful “pop” under 1st metatarsal head

quadratus plantae realigns direction of which muscle?

flexor digitorum longus

tibialis posterior dysfunction →

flat foot [pes planus]

severance/damage to tibial nerve →

complete loss of plantarflexion, toe flexion, sensory anesthesia across sole of foot [medial & lateral plantar nerves arise from tibial nerve]

fibular [peroneal] artery supplies

popliteus, posterior & lateral compartments

• largest branch of posterior tibial artery

joint motion of ankle [talocrural] joint

dorsiflexion & plantarflexion

joint motion of subtalar joint

inversion & eversion

joint motion of transverse tarsal joint

adduction & abduction

forefoot varus

medial column elevated

compensation calcaneus shifts into valgus → risk lateral calcaneofibular impingement

forefoot valgus

medial column excessively plantarflexed

compensation calcaneus shifts into varus → ankle instability

elftman concept / subtalar locking mechanism

• everted calcaneus [heel strike]

  • joint axes parallel → increase flexibiloity for shock absorption

• inverted calcaneus [toe-off]

  • joint axes nonparallel [incongruent] → locks midfoot for push-off

windlass mechanism

tightening of plantar aponeurosis [from toe extension & raising arch]

• synergizes w/ achilles tendon tension to invert subtalar joint, creating rigid lever for toe-off

talus

• has body, neck, & head

• no muscular or tendinous attachments

• posterior process marked by a groove for FHL tendon

  • if process fails, bone know as os trigonum

sulcus tali

inferior groove forming tarsal canal w/ calcaneus

trochlea tali

smooth superior saddle forming main ankle joint

talcalcaneonavicular [TCN] joint complex

formed by combo of talus, calcaneus, spring ligament, & navicular

cuboid

• articulates proximally w/ distal calcaneus via curved saddle shaped joint

• medially articulates w/ navicular & lateral cuneiform

• distally articulates w/ 4th & 5th metatarsal bases

• oblique sulcus/groove houses tendon of fibularis longus as it travels across 1st metatarsal bone

joint type of navicular-cuneiform & intercuneiform

plane [gliding] synovial joints

cuboid syndrome

trauma or excessive inversion can sublux cuboid → sharp lateral foot pain during weight bearing

often misdiagnosed w/ ankle sprain

navicular

• keystone bone

• supports medial longitudinal arch

• navicular tuberosity

  • insertion site for tibialis posterior

• accessory navicular

  • detached navicular tuberosity found in 11-14% of pop

    • secondary ossification center [os tibiale externum]

    • within tibialis posterior tendon

    • prominent medial bump can cause painful tendinitis from shoewear

muscles of foot [20 intrinsic muscles]

plantar aspect: 14

dorsal : 2

intermediate layer [interossei]: 4

muscles innervated by medial plantar nerve

LAFF

• Lumbricals [1st one]

• Abductor hallucis

• Flexor digitorum brevis [FDB]

• Flexor hallucis brevis [FHB]

saphenous nerve innervates

medial foot to head of 1st metatarsal

superficial fibular nerve innervates

most of dorsum of foot & toes [except 1st webspace]

deep fibular nerve innervates

1st webspace

medial & lateral plantar nerves [from tibial] innervate

sole of foot

sural nerve innervates

lateral side of foot

calcaneal branches [tibial & sural] nerve innervate

posterior heel

dorsalis pedis artery courses between

EHL & EDL tendons

branches of dorsalis pedis artery

• lateral tarsal artery

  • under EDB

• arcuate artery

  • gives rise to 2nd-4th dorsal metatarsal arteries

• 1st dorsal metatarsal artery

  • to great toe & 2nd toe

• deep plantar artery

  • dives into sole to join deep plantar arch

posterior tibial artery →

• medial plantar artery

  • small, supplies great toe muscles & skin

• lateral plantar artery

  • forms deep plantar arch [joins deep plantar artery from dorsum]

• branches

  • plantar metatarsal

  • plantar digital arteries

  • perforating branches

extensor digitorum brevis contusion

• commonly mistaken for edema near lateral malleolus

• injury → hematoma & swelling

medial plantar nerve entrapment

“jogger’s foot”

• compression under abductor hallucis

• causes burning, numbness, tingling on medial sole/navicular area

symptomatic flexible flatfoot

• present in teens

• associated w/ achilles equinus contracture [tightness]

tarsal coalition

• failure of hindfoot segmentation

• becomes rigid/symptomatic in adolescence as cartilaginous bar ossifies

• presents w/ peroneal spastic flatfoot

pes cavus

high arch

calcaneus inverted >3 degrees

pes planus

• medial bulge

• abducted foot

• everted calcaneus

sustentaculum tali

• horizontal bony shelf on inner [medial] side of calcaneus

• groove holds tendon of FHL

  • tarsal tunnel contents funnel thru this groove