Lower Leg

Introduction

plantarflexion: point toes like in ballet

dorsiflexion: use extensors of foot to bring toes towards head

eversion: like pronation in arm; sole of foot points laterally

inversion: like supination in arm; sole of foot points medially

nerves:

tibial: posterior leg and sole of foot

deep branch of fibular: dorsoflexors of anterior compartment; damage results in foot drop (common because the common fibular nerve runs superficial and lateral to the fibular head)

superficial branch of fibular: lateral muscles

flat feet: despite what the books say, the real function of the intrinsic muscles of the foot is to support the arch of the foot and by eccentric contraction to act as shock absorbers; lack of an arch means no shock absorption Þ fatigue fractures result from extensive walking, marching, etc.

triceps surae: gastocnemius and soleus muscles

Tom, Dick, and Harry: posterior to the medial malleolus runs (from anterior to posterior): tibialis posterior tendon (Tom); flexor digitorum longus tendon (Dick); posterior tibial vein; posterior tibial artery; tibial nerve; flexor hallucis longus tendon (Harry)

plantaris muscle: like the palmaris longus, of little clinical relevence except that is has a long tendon that can be used in repairs of other tendons and ligaments

Pott’s fracture: the deltoid ligament is strong; forceful eversion of the foot can break off part of the medial malleolus to which it is attached

PAD: plantar interosseous adduct

DAB: dorsal interosseus abduct

Anterior Muscles of Leg

tibialis anterior

origin: lateral condyle of tibia; upper 2/3 of lateral tibia; interosseus membrane; lat. intermuscular septum

insertion: medial and plantar surface of medial cuneiform bone; base of 1^st metatarsal bone

innervation: deep fibular (peroneal) nerve

action: dorsiflexion of foot; inverts foot

extensor hallucis longus

origin: middle half of anterior surface of fibula; adjacent interosseous membrane

insertion: base of distal phalanx of great toe

innervation: deep fibular (peroneal) nerve

action: extends great toe; dorsiflexes foot

extensor digitorum longus

origin: lateral condyle of tibia; upper 3/4 of fibula and interosseus membrane

insertion: dorsal surface of middle and distal phalanges of lateral 4 toes

innervation: deep fibular (peroneal) nerve

action: extends phalanges of lateral 4 toes; dorsiflexes foot

fibularis (peroneus) tertius

origin: lower anterior surface of fibula; adjacent intermuscular septum

insertion: dorsal surface of base of 5^th metatarsal bone

innervation: deep fibular (peroneal) nerve

action: dorsiflexes and everts foot

Posterior Muscles of Leg - superficial

gastrocnemius

origin:

medial head: medial condyle and adjacent femur; capsule of knee joint
lateral head: lateral condyle and adjacent femur; capsule of knee joint

insertion: calcaneus via calcaneal tendon

innervation: tibial nerve

action: plantarflexes foot; flexes femur on tibia

soleus

origin: posterior surface of head, upper 1/3 of fibula; middle 1/3 of medial border of tibia; tendon between tib/fib

insertion: calcaneus via calcaneal tendon

innervation: tibial nerve

action: plantarflexes foot; steadies leg upon foot

plantaris

origin: lateral supracondylar line of femur; oblique popliteal ligament of knee joint

insertion: medial/posterior side of calcaneus; clacaneal tendon

innervation: tibial nerve

action: plantarflexes foot

Posterior Muscles of Leg - deep

popliteus

origin: lateral condyleof femur; oblique popliteal ligament of knee

insertion: posterior tibia above soleal line

innervation: tibial nerve

action: flexes leg; rotates tibia medially at beginning of flexion

flexor hallucis longus

origin: lower 2/3 of posterior surface of fibula; interosseous membrane

insertion: base of distal phalanx of great toe

innervation: tibial nerve

action: flexes great toe; aids in plantarflextion of foot

flexor digitorum longus

origin: posterior of middle 3/5 of tibia; fascia of tibialis posterior

insertion: plantar surface of base of distal phalanx of lateral 4 toes

innervation: tibial nerve

action: flexes phalanges of lateral 4 toes; plantarflexes foot

tibialis posterior

origin: lateral part of posterior surface of tibia; upper 2/3 of medial surface of fibula; interosseous membrane

insertion: tuberosity of navicular bone; plantar surfaces of all cuneiform bones; plantar surface of base of metatarsals 2-4; cuboid bone; sustentaculum tali

innervation: tibial nerve

action: plantarflexes and inverts foot

Lateral Muscles of Leg

fibularis (peroneus) longus

origin: lateral condyle of tibia; upper 2/3 of lateral surface of fibula

insertion: lateral side of medial cuneiform bone; base of 1^st metatarsal bone

innervation: superficial fibular (peroneal) nerve

action: plantarflexes and everts foot

fibularis (peroneus) brevis

origin: lower 2/3 of lateral surface of fibula

insertion: lateral side of base of 5^th metatarsal

innervation: superficial fibular (peroneal) nerve

action: plantarflexes and everts foot

Muscles of the Foot – plantar surface

First Layer

abductor hallucis

origin: medial process of calcaneus; flexor retinaculum; plantar aponeurosis

insertion: medial side of proximal phalanx of great toe

innervation: medial plantar nerve

action: arch support; abduction and flexion of great toe

flexor digitorum brevis

origin: medial process of calcaneus; plantar aponeurosis; adjacent intermuscular septum

insertion: middle phalanx of lateral 4 toes

innervation: medial plantar nerve

action: arch support; flexion of lateral 4 toes

abductor digiti minimi

origin: lateral and medial processes of calcaneus; plantar aponeurosis; adjacent intermuscular septum

insertion: lateral side of base of proximal phalanx of fifth toe

innervation: lateral plantar nerve

action: arch support; abducts and flexes fifth toe

Second Layer

quadratus plantae

origin: medial surface and lateral margin of calcaneus

insertion: posterolateral margin of tendon of flexor digitorum longus

innervation: lateral plantar n

action: adjusts and straightens the pull of the flexor digitorum longus tendon

lumbricals

origin: tendons of flexor digitorum longus

insertion: bases of terminal phalanges of lateral four toes

innervation: lateral plantar n; 1^st lumbercal by medial plantar n

action: flex toes at MP joints; extend at phalangeal joints

Third Layer

flexor hallucis brevis

origin: plantar surfaces of cuboid and lateral cuneiform bones

insertion: base of proximal phalanx of great toe

innervation: medial plantar nerve

action: arch support; flexes proximal phalanx of great toe

adductor hallucis

origin: oblique head: bases of metatarsals 2-4; transverse head: plantar ligaments of MP joints

insertion: lateral side of proximal phalanx of great toe

innervation: lateral plantar nerve

action: arch support; adducts great toe

flexor digiti minimi brevis

origin: base of 5^th metatarsal

insertion: base of proximal phalanx of 5^th toe

innervation: lateral plantar nerve

action: arch support; flexes proximal phalanx of 5^th toe

Fourth Layer

plantar interossei

origin: bases and medial sides of metatarsals 3-5

insertion: medial sides of bases of proximal phalanges 3-5

innervation: lateral plantar nerve

action: transverse arch support; adduct digits 2-4; flex MP joints

dorsal interossei

origin: adjacent sides of metatarsal bones 1-5

insertion: 1^st: medial side of proximal phalanx of 2^nd digit; 2-4: lateral sides of digits 2-4

innervation: lateral plantar n

action: transverse arch support; abduction of digits 2-4; flexion of MP joints

Bones

adductor tubercle: superior surface of medial condyle of femur; inferior insertion of adductor magnus

tibia: 2^nd largest bone of body; located on anteromedial side of leg (shin bone); proximal end is large

plateau articulates with femur, intercondylar eminence fits into intercondylar notch of femur; distal end articulates with talus and fibula; distolateral end forms medial malleolus

soleal line: one of orgins of soleus muscle; runs inferomedially from lateral condyle of tibia on posterior surface

middle malleolus: distal-lateral portion of tibia; lies proximal to lateral malleolus; has groove for tendons of tibialis posterior (Tom), and flexor digitorum longus (Dick)

fibula: posterolateral aspect of leg; functions for muscle attachment, support of tibia, stabilization of talus; no weight bearing function; proximal head articulates with lateral condyle of tibia; distal aspect forms lateral malleolus and articulates with tibia and talus

lateral malleolus: inferior lateral border of fibula; slightly more distal than medial malleolus; has groove for tendons of fibularis brevis (slides along the fibula) and longus (slides along the brevis tendon)

talus: most proximal bone of foot; articulates with tibia, fibula, calcaneus, navicular bones; has groove on posterior aspect between two tubercles for tendons of flexor hallucis longus (Harry)

fibular trochlea: superior surface of the talus where it articulates with the tibia

calcaneus: largest, strongest bone of foot; forms the heel of the foot; articulates with talus and cuboid

sustentaculum tali: shelf on which the inferomedial part of the talus rests; comes off of superomedial aspect of calcaneus

cuboid: most lateral bone in the distal row of the tarsus

navicular: articulates with calcaneus, cuneiform, and sometimes the cuboid

cuneiforms (1-3)

metatarsals (1-3)

phalanges (14)

Nerves

tibial nerve from ventral rami L4-S3 (anterior divisions of sacral plexus); larger terminal branch of sciatic nerve; runs through popliteal fossa posterior to the popliteal vessels, dives under the soleus and runs along the tibialis posterior muscle, passes deep to the flexor retinaculum and divides into the medial and lateral plantar nerves posterior to the medial malleolus; supplies the muscles in the posterior compartment of the leg

common fibular nerve from ventral rami L4-S2 (posterior divisions of sacral plexus); smaller terminal branch of sciatic; runs through the popliteal fossa along the biceps femoris muscle and tendon, wraps around the neck of the fibula and branches on the anterolateral surface of the leg to the superficial and deep fibular nerves

deep fibular nerve branches from the common fibular just distal to the head of the fibula; runs along the anterior surface of the interosseous membrane, passes deep to the extensor retinaculum and divides into lateral and medial branches; supplies muscles of anterior compartment of leg, skin of the first web space

superficial fibular nerve branches from common fibular just distal to the fibular neck, runs between the fibular muscles and the extensor digitorum longus; supplies lateral compartment muscles, skin of anterior distal surface of leg, most of dorsum of foot, and most of digits

medial plantar nerve branch of tibial nerve; supplies abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, first lumbrical

lateral plantar nerve branch of tibial nerve; supplies muscles of foot not supplied by the lateral plantar nerve

Arteries

anterior tibial: smaller branch of popliteal; runs on anterior surface of interosseus membrane; becomes dorsalis pedis midway between the malleoli

dorsalis pedis: continuation of anterior tibial distal to the ankle; runs on dorsum of foot; at MP joint, branches to arcuate artery, deep plantar artery, 1^st dorsal metatarsal artery

arcuate artery of foot: branch of dorsalis pedis, runs medial to lateral along MP joints; anastamoses with lateral tarsal artery between the 4^th and 5^th MP joints

posterior tibial: larger terminal branch of popliteal; begins at distal border of popliteus muscle, gives off fibular artery; accompanies tibial nerve along posterior aspect of tibialis posterior muscle; runs posterior to medial malleolus

fibular: branch of the posterior tibial artery at the superior border of the soleus; runs along medial aspect of fibula

lateral plantar: larger of terminal branches of posterior tibial artery; runs obliquely from the medial part of the heel to the middle of the 5^th metatarsal where it forms the lateral aspect of the plantar arch

medial plantar: smaller of terminal branches of posterior tibial artery; runs along medial side of foot

medial malleolar and lateral malleolar: medial and lateral branches of the anterior tibial artery; contribute to arterial network around the malleoli

Miscellaneous

crural fascia: continuation of fascia lata of thigh, encases the leg in a tense sheath which helps aid in the calf-pump action of venous return; too much exercise, or too quick can make the muscles swell and cut off their own blood supply Þ ‘shin splints’

sesamoid bones: on either side of the tendons of the flexor hallucis brevis muscle; prevent compression of the tendon by the first metatarsal during standing, walking, etc

superior extensor retinaculum: extends from tibia to fibula proximal to the malleolus; prevents bowstringing of extensor tendons

inferior extensor retinaculum: two heads: from medial malleolus and medial part of plantar aponeurosiscrosses the extensor tendons and attaches to the anterior-superior surface of the calcaneus

compartments of leg

anterior: tibialis anterior, extensor hallucis longus, extensor digitorum longus, fibularis tertius, deep fibular nerve, anterior tibial artery

posterior: gastocnemuis, soleus, planteris, popliteus, flexor hallucis longus, flexor digitorum longus, tibialis posterior; tibial nerve, posterior tibial artery, fibular artery

lateral: fibularis longus, brevis; superficial fibular nerve

crural intermuscular septa: fascial divisions of the compartments of the leg

deltoid ligament: medial ligament of ankle; attaches medial malleolus to the talus, calcaneus, navicular bones; much stronger than the lateral ligaments which is one of the reasons why lateral sprains are more common

plantar aponeurosis: thickening of the plantar fascia; originates on the calcaneus, runs length of foot on the plantar surface and splits into five divisions which enclose the digits; also has two vertical septa which divide the foot into lateral, medial, and central compartments (but foot is usually described in layers instead); is lax when foot is at rest, but during walking, running, etc provides much arch support; cutting the aponeurosis leads to flat feet within a few years

Hip Joint – ball and socket, synovial joint; weight bearing surface is ilial aspect of acetabulum

iliofemoral ligament: runs from anterior inferior iliac spine to the intertrocanteric line of the femur; keeps the pelvis from falling backwards on the legs when in a standing position

acetabulum: socket of the hip joint; is rimmed by the acetabular labrum which is a fibrocartilagenous lip deepening the socket and providing more surface area for articulation

lunate articular surface: articular surface of the acetabulum

joint capsule: proximal attachement to rim of acetabulum, distal to the intertrochanteric line and to the posterior part of theneck proximal to the intertrochanteric crest; made up of the iliofemoral ligament (see above); pubofemoral ligament (pubic part of acetabular rim, blends with iliofemoral - prevents over abduction of the hip); ischiofemoral ligament (ischial rim of acetabulum to neck of femur medial to greater trochanter - prevents hyperextension of hip)

ligament of head of femur: relatively weak ligament inside the joint capsule that attaches the head to the acetabulum; important because it contains the artery to the head of the femur (branch of obturator) Þ rupture of ligament can lead to necrosis of the head

articular area of head of femur: forms about 2/3 sphere; covered in hyaline cartilage except over attachment of ligament of head of femur

Knee Joint – hinge-type synovial joint; three articulations (patella/femur; lateral and medial between femur and tibia)

ligamentum patellae: continuation of quadriceps tendon; patella is actually a sesamoid bone in this ligament; attaches to tibial tubercle on anterior surface of tibia

lateral (fibular) collateral ligament: LCL; thin, pencil-like round ligament; from lateral epichondyle of femur to lateral surface of head of fibula; tendon of the popliteus muscle runs under the LCL, so there is no attachment of the LCL and the lateral meniscus of the knee

medial (tibial) collateral ligament: flat band of ligament; from medial epichondyle of femur to medial condyle and superior medial surface of tibia; partly continuous with the adductor magnus tendon; is attached to the medial meniscus of knee

posterior cruciate ligament: stonger of the cruciate ligaments; posterior part of intercondylar area to anterior part of lateral surface of the medial condyle of the femur; prevents anterior displacement of the femur on the tibia, or posterior displacement of the tibia on the femur

anterior cruciate ligament: weaker of the two ligaments; anterior part of intercondylar area to the medial surface of the lateral condyle of the femur; prevents posterior displacement of femur on tibia and hyperextension of knee joint

menisci of knee: fibrocartilage shock absorbers of knee; wedge-shapes that fill the gaps in the articulation of the femur and tibia

lateral meniscus: nearly a closed circle of fiborcartilage; separated from the LCL by the tendon of the popliteus, so the lateral meniscus is more freely movable

medial meniscus: C-shaped fibrocartilage; attaches to the MCL; immobile Þ MCL tear can damage the meniscus

prepatellar bursa: between the patella and the skin, allows skin to move easily over the patellla

suprapatellar bursa: extension of the synovial capsule that fits under the quadriceps tendon permitting free movement

terrible triad: receiving a blow to the lateral aspect of the knee can tear the MCL; this may lead to tearing of the medial meniscus (because the two are attached); and then lead to tearing of the ACL

anterior drawer sign: grasping the tibia and pulling anteriorly with the leg flexed will demonstrate a damaged or destroyed ACL

posterior drawer sign: pushing the tibia posteriorly with the leg in flexion will demonstrate a damaged or destroyed PCL

Ankle

deltoid ligament: medial ligament of ankle; attaches medial malleolus (tibia) to the talus, navicular, calcaneous bones

lateral ligaments of ankle: much weaker than deltoid

calcaneofibular ligament: tip of lateral malleolus to the lateral surface of the calcaneous
anterior talofibular ligament: lateral malleolus to the neck of the talus
posterior talofibular ligament: malleolar fossa to the lateral tubercle of the posterior process of the talus