The leg, ankle, and foot

Overview

Bones and joints

Bones of the leg

Tibia

Medial bone of the leg

  • Important landmarks
    • Tibial condyles: horizontal upper surface of the tibia with medial and lateral depressions that articulate with the femoral condyles
    • Tibial tuberosity
    • Shaft: has 3 surfaces (anterior, lateral, and posterior)
    • Medial malleolus: inferomedial projection of the distal end of the tibia
  • Function
    • Weight-bearing bone
    • Articulates superiorly with the femoral condyles to form the knee joint
    • Articulates with the talus to form a portion of the ankle joint
    • Articulates with the fibula proximally and distally
    • Site of attachment of lower extremity muscles

Fibula

Lateral bone of the leg; non-weight bearing

Joints of the leg

Tibiofibular joints

  • Proximal tibiofibular joint: synovial joint between the head of the fibula and the lateral tibial condyle
  • Distal tibiofibular joint: fibrous joint (syndesmosis) between the distal ends of the tibia and fibula

Interosseous membrane of the leg

Fibrous connective tissue that extends between the medial border of the fibula and the lateral border of the tibia

  • Important landmark: A notch at the superior end permits the anterior tibial vessels to enter the anterior compartment of the leg.
  • Function
    • Stabilizes the tibiofibular joints
    • Site of attachment of numerous leg muscles

Bones of the ankle (tarsal bones)

Seven tarsal bones make up the ankle joint

Tarsal bones Characteristics
Talus
  • Most superior tarsal bone
  • Has a groove for the interosseous ligaments
  • Has a groove for the tendon of the flexor hallucis longus
  • Articulations
  • Transmits bodyweight from the tibia to the calcaneus
  • Forms part of the medial longitudinal arch of the foot
Calcaneus
  • Located beneath the talus bone
  • Has an inferior groove for the tendon of the flexor hallucis longus
  • Articulations
    • Superior: talus
    • Anterior: cuboid bone (calcaneocuboid joint)
  • Forms the heel of the foot
  • Transmits bodyweight from the talus to the ground
  • Site of attachment for the Achilles tendon
Navicular
  • Boat-shaped bone located medially in the proximal foot
  • Has a tuberosity on its inferior surface to which the tibialis posterior tendon is attached
  • Articulations
Cuneiform
Cuboid
  • Most lateral tarsal bone
  • Contains a groove for the tendon of the fibularis longus (peroneus longus) muscle
  • Articulations
    • Anterior: 4th metatarsal bone
    • Anterolateral: 5th metatarsal bone
    • Posterior: calcaneus
    • Medial: lateral cuneiform and the cuboid
  • Forms part of the lateral longitudinal arch of the foot

Ankle joint

  • Type: synovial hinge joint
  • Components: the talus with the tibia and fibula
  • Ligaments
    • Medial ligament (deltoid ligament)
    • Lateral ligament
  • Movements (uniaxial)
    • Flexion (plantarflexion)
    • Extension (dorsiflexion)

Bones and joints of the foot

Arches of the foot

There are 3 arches in the foot: two longitudinal and one transverse

Arch Characteristics
Medial longitudinal arch
Lateral longitudinal arch
Transverse arch
  • Formed by bases of the 5 metatarsals, the cuboid, and the 3 cuneiforms
  • Supported by fibularis longus and tibialis posterior
  • Function
    • Distribute the body weight
    • Act like springs and shock absorbers while running and walking
  • Clinical significance

Fascia and retinacula of the foot

  • Plantar fascia (plantar aponeurosis)
    • Thick band of connective tissue that extends from the calcaneal tuberosity to the plantar aspect of the proximal phalanges of the toes
    • Supports the bony arches of the foot
    • Plays an important role in the dynamics of the foot
    • Clinical significance: plantar fasciitis

Anterior retinacula

(Extensor retinacula)

Medial retinaculum

(Flexor retinaculum)

Lateral retinacula

  • Superior extensor retinaculum of the ankle
    • Thick transverse band of fascia that extends from the anterior surface of the tibia to the anterior surface of the fibula
    • Tendons of the anterior compartment of the leg, the anterior tibial vessels, and the deep peroneal nerve pass under it.
  • Inferior extensor retinaculum of the ankle
    • Transverse Y-shaped band of fascia that extends from the medial malleolus (upper arm of Y) and plantar aponeurosis (lower arm of Y) medially to the lateral aspect of the calcaneus (base of Y)
    • Tendons of the anterior compartment pass under it.
  • Thich oblique band of fascia that extends from the medial malleolus to the medial aspect of the calcaneus
  • Tendons of the deep posterior compartment, the posterior tibial vessels, and the tibial nerve pass under it.
  • Superior peroneal retinaculum: extends from the lateral malleolus to the lateral aspect of the calcaneus
  • Inferior peroneal retinaculum: a continuation of the lateral aspect of the inferior extensor retinaculum
  • They hold the two tendons of the lateral compartment of the leg in place.

Muscles

Muscles of the leg

  • The muscles of the leg exert their action on the ankle, foot, and toes
  • The deep fascia of the leg divides these muscles into three compartments
    • Anterior compartment
      • Common nerve supply: deep peroneal nerve
      • Common function: dorsiflexion of the ankle (extension)
    • Posterior compartment
      • Common nerve supply: tibial nerve
      • Common function: plantarflexion of the ankle (flexion)
    • Lateral compartment

Anterior compartment of the leg

(Extensor compartment)

Muscle Origin Insertion Innervation Function

Testing

Tibialis anterior
  • Lateral tibial condyle, proximal 2/3rd of lateral surface of tibial shaft, and the adjacent interosseous membrane
  • Medial cuneiform and base of the 1st metatarsal bone
Deep peroneal nerve
  • Dorsiflex the foot against resistance
Extensor hallucis longus (EHL)
  • Middle 1/3rd of the medial surface of the fibula and the adjacent interosseous membrane
  • Dorsal aspect of the base of the distal phalanx of the hallux (big toe)
  • Extend the hallux against resistance
Extensor digitorum longus(EDL)
  • Lateral tibial condyle, proximal 2/3rd of the medial surface of the fibula and the adjacent interosseous membrane
  • Divides into 4 tendons that insert into the bases of the middle and distal phalanges of the 2nd–5th toes
  • Lateral 4 toes: extension
  • Ankle joint: dorsiflexion (weak)
  • Extend the lateral 4 toes against resistance
Peroneus tertius
  • Distal 1/3rd of the medial surface of the fibula and the adjacent interosseous membrane
  • Dorsal aspect of the base of the 5th metatarsal bone
  • Ankle joint: dorsiflexion (weak)
  • Foot: inversion (weak)
  • Cannot be tested in isolation

Posterior compartment of the leg

(Flexor compartment)

Group Muscle Origin Insertion Innervation Function Testing
Superficial flexor group Gastrocnemius
  • Lateral head: lateral femoral condyle
  • Medial head: medial femoral condyle
  • Ankle: plantar flexion
  • Knee: flexion
  • Plantar flex the ankle against resistance with the knee extended
Soleus
  • Head of fibula and middle 1/3rd of the medial border of the tibia (soleal line)
  • Ankle: plantar flexion
  • Plantar flex the ankle against resistance with the knee flexed
Plantaris
  • Lateral supracondylar line of the femur
  • Ankle: plantar flexion (weak)
  • Cannot be tested in isolation
Deep flexor group Tibialis posterior
  • Posterior surfaces of the upper parts of the fibula and tibia and the adjacent interosseous membrane
  • Foot: Inversion (main foot inverter)
  • Invert a plantarflexed foot against resistance
Flexor digitorum longus
(FDL)
  • Posterior surface of the tibia
  • Splits into 4 tendons that insert into the base of the distal phalanges of the lateral 4 toes
  • Lateral 4 toes: flexion of the distal phalanges
  • Flex the lateral 4 toes against resistance
Flexor hallucis longus
(FHL)
  • Distal 2/3rd of the posterior aspect and the adjacent interosseous membrane
  • Plantar aspect of base of the distal phalanx of the hallux
  • Hallux: flexion
  • Flex the hallux against resistance
Popliteus
  • Tendinous origin from knee joint capsule and lateral femoral condyle
  • Head of the fibula (medial surface)
  • Internally rotates the tibia on the femur (unlocking the fully extended knee)
  • Cannot be tested in isolation

Lateral compartment of the leg

(Peroneal or fibular compartment)

Muscle Origin Insertion Innervation Function Testing

Peroneus longus

(fibularis longus)

  • Head and proximal 2/3rd of the lateral surface of fibula
  • Lateral aspects of the base of the 1st metatarsal and the medial cuneiform bones
  • Ankle: plantarflexion
  • Foot: eversion
  • Tested together by everting the foot against resistance

Peroneus brevis

(fibularis brevis)

  • Distal 2/3rd of the lateral surface of fibula
  • Lateral aspect of the base of the 5th metatarsal bone
  • Foot: eversion

Muscles of the foot

  • The muscles of the foot are divided into two groups based on where the muscle belly is located.
  • Extrinsic muscles of the foot: muscle bellies are located in the leg (see “muscles of the leg” above)
  • Intrinsic muscles of the foot: muscle bellies are located within the foot
    • Dorsal intrinsic muscles: innervated by the deep fibular nerve
    • Plantar intrinsic muscles: innervated by branches of the tibial nerve (medial and lateral plantar nerves)
    • Tested by asking the examinee to perform the action of the muscle against resistance
Layer of the foot Muscle Origin Insertion Innervation Function
Muscles of the dorsum of the foot Extensor digitorum brevis
  • Lateral 4 toes: extension at the MTP and IP joints
Extensor hallucis brevis
  • Base of the proximal phalanx of the hallux
  • Hallux: extension at the MTP and IP joints
Muscles of the sole of the foot (superficial to deep) First layer Abductor hallucis
  • Base of the proximal phalanx of the hallux
  • Medial plantar nerve
  • Hallux: abduction
Flexor digitorum brevis
  • Medial plantar nerve
  • Lateral 4 toes: flexion at PIP joint
Abductor digiti minimi
  • Proximal phalanx of the 5th toe
  • Lateral plantar nerve
  • 5th toe: abduction

Second layer

Quadratus plantae
  • Lateral plantar nerve
  • Lateral 4 toes: flexion
Lumbricals
  • Extensor expansion of the lateral 4 toes
  • First lumbrical: medial plantar nerve
  • Lateral three: lateral plantar nerve
  • Flexion of MTP joints
  • Extension of IP joints
Third layer Flexor hallucis brevis
  • Base of the proximal phalanx of the hallux
  • Medial plantar nerve
  • Hallux: flexion at MTP
Adductor hallucis
  • Proximal phalanx of the big toe
  • Lateral plantar nerve
  • Hallux: adduction
Flexor digiti minimi brevis
  • Base of the 5th metatarsal bone
  • Proximal phalanx of the 5th toe
  • Lateral plantar nerve
  • 5th toe: flexion at MTP
Fourth layer

Plantar interossei

(3)

  • Medial side on the base of the proximal phalanges 3–5
  • Lateral plantar nerve
  • Lateral 4 toes: adduction
Dorsal interossei (4)
  • Lateral plantar nerve
  • 2nd–4th toes: abduction

Vasculature

Arteries of the leg

Anterior tibial artery

Posterior tibial artery

Fibular artery

(peroneal artery)

Origin
Course
  • Begins in the popliteal fossa, at the inferior border of the popliteus muscle
  • Enters the anterior compartment of the leg through a gap in the upper part of the interosseous membrane
  • Lies on the interosseous membrane throughout its course
  • Lies between the two malleoli at the ankle joint
  • Continues as the dorsalis pedis artery beyond the ankle joint
  • Begins in the popliteal fossa, ∼ 2.5 cm below the popliteus muscle
  • Travels along the medial border of the fibula
  • Ends at the inferior tibiofibular joint by dividing into calcaneal branches
Branches
  • Recurrent branches to the anastomosis around the knee joint
  • Muscular branches
  • Medial and lateral malleolar branches
  • A circumflex branch to the knee
  • Muscular branches
  • Medial malleolar and calcaneal branches
  • Muscular branches
Supply
  • Anterior compartment of the leg
  • Posterior compartment of the leg
  • Plantar aspect of the foot
  • Lateral and deep flexor compartments of the leg
Important relations

Arteries of the foot

Dorsum of the foot

  • Dorsalis pedis artery
    • Origin: continuation of the anterior tibial artery beyond the ankle joint
    • Course
      • Travels in the 1st intermetatarsal space, lateral to the tendon of the EHL
      • Passes through the 1st dorsal interosseus muscle and enters the sole
      • Ends by anastomosing with the lateral plantar artery and giving off the 1st dorsal metatarsal artery
      • The dorsalis pedis artery is often aberrant or absent
    • Branches
      • Tarsal arteries
      • Arcuate artery: which gives rise to the lateral 3 dorsal metatarsal arteries, from which the digital arteries arise

Sole of the foot

  • Branches of the posterior tibial artery
    • Medial plantar branch: supplies the medial side of the sole
    • Lateral plantar branch: supplies the lateral side of the sole and anastomosis with the dorsalis pedis
  • Plantar arterial arch
    • Formed by the anastomosis between the dorsalis pedis and lateral plantar arteries
    • Located on the plantar aspect of the bases of the lateral 4 metatarsal bones
    • Branches: 4 plantar metatarsal arteries

Veins of the leg

Superficial veins

The superficial veins lie within the subcutaneous tissue. There are two main superficial veins of the leg:

  • Great saphenous vein (GSV)
    • Origin: continuation of the medial marginal vein of the foot (medial end of the dorsal venous arch)
    • Course
      • At the ankle: passes in front of the medial malleolus
      • In the leg: ascends along the medial aspect of the shin
      • At the knee: behind the medial condyles of the femur and tibia
      • Thigh: medial aspect of the thigh
    • Termination: saphenofemoral junction (SFJ)
      • The site at which the GSV passes through the saphenous opening in the deep fascia of the thigh to meet the femoral vein
      • The position is fairly constant at 4 cm below and lateral to the pubic tubercle.
    • Main tributaries:
      • Short saphenous vein
      • Superficial external pudendal vein
      • Superficial epigastric veins
      • Superficial circumflex iliac vein
      • Lateral femoral cutaneous vein
    • Drains: the anteromedial aspect of the sole, leg, and thigh
    • Important relations: saphenous nerve accompanies the GSV below the knee
    • Clinical significance
  • Small saphenous vein (SSV)
    • Origin: continuation of the lateral marginal vein of the foot (lateral end of the dorsal venous arch
    • Course:
      • At the ankle: passes behind the lateral malleolus
      • In the leg: ascends in the midline of the calf towards the popliteal fossa
    • Termination: saphenopopliteal junction (SPJ)
      • The site at which the SSV drains into the popliteal vein
      • Unlike the SFJ, the location of the SPJ is variable, lying within, proximal, or distal to the popliteal fossa
    • Important relations: sural nerve accompanies the SSV through most of its course

Deep veins of the leg

  • The deep veins lie deep to the deep fascia
  • They accompany the arteries of the leg
    • Anterior tibial veins
    • Posterior tibial veins
    • Fibular veins (peroneal veins)
  • These deep veins join at the inferior border of the popliteus muscle to form the popliteal vein.
  • Clinical significance: deep vein thrombosis

Veins of the foot

  • Digital veins (on the sides of the toes) → metatarsal veins (in the intermetatarsal spaces) → deep plantar venous arch (plantar aspect of the lateral 4 metatarsal bones) → medial and lateral plantar veins → GSV and SSV

References:[1][2][3][4]

Innervation

Motor and sensory innervation

Nerve Origin Motor supply Sensory supply Clinical significance
Mixed motor and sensory nerves Tibial nerve
  • A terminal branch of the sciatic nerve
  • Arises at the apex of the popliteal fossa
  • Nerve roots: ventral divisions L4–S3
  • Posterior compartment of the leg
  • Sural nerve (see below)
  • Medial calcaneal branch: skin over the heel (not shown in image)
  • Medial plantar nerve: medial half of the sole (excluding the heel) and the plantar aspect of medial 3.5 toes
  • Lateral plantar nerve: lateral half of the sole (excluding the heel) and the plantar aspect of the lateral 1.5 toes
Common peroneal nerve
(common fibular nerve)
  • A terminal branch of the sciatic nerve
  • Arises at the apex of the popliteal fossa
  • Nerve roots: dorsal divisions L4–S2
  • Course
    • Travels along lateral border of the popliteal fossa
    • Winds around the neck of the fibula where it terminates by dividing into the superficial and deep peroneal nerves
  • None
  • Lateral sural cutaneous nerve (lateral cutaneous nerve of calf): skin over the lateral aspect of the leg
  • Sural communicating nerve: joins the tibial part of the sural nerve
Deep peroneal nerve
  • Anterior compartment of the leg
  • 1st web space of the foot (i.e., the sandal gap)
Superficial peroneal nerve
  • Lateral comaprtment of the leg
  • Distal part of the anterior aspect of the leg and the dorsum of the foot (except the 1st web space)
Pure sensory nerves Saphenous nerve
  • None
  • Skin over the medial half of the leg
Sural nerve
  • Formed by the union of sural branches from the tibial and common peroneal nerves
  • None
  • Skin over the posterolateral aspect of the distal 1/3rd of the leg and the lateral border of the foot

TIPPED = tibial nerve versus peroneal nerve
TIP = Tibial nerve Inverts and Plantarflexes the foot → cannot walk on TIPtoes when injured
PED = Peroneal nerve Everts and Dorsiflexes the foot → foot drop when injured

Dermatomal distribution of the leg and foot

  • Anterior leg
    • Medial 1/3rd: L4
    • Middle 1/3rd: L5
    • Lateral 1/3rd: S1
  • Posterior leg
    • Medial 1/3rd: L4
    • Middle 1/3rd: S2
    • Lateral 1/3rd: S1
  • Dorsal and plantar aspects of the foot
    • Medial 1/2: L5
    • Lateral 1/2: S1

Clinical significance