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 Anatomy Function
Talus
  • Most superior tarsal bone
  • 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
  • Articulations
    • Superior: talus
    • Anterior: cuboid bone (calcaneocuboid joint)
  • Forms the heel of the foot and 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
  • Articulations
Cuneiform
  • Forms part of the proximal transverse and medial longitudinal arches of the foot
Cuboid
  • Forms part of the lateral longitudinal arch of the foot

Ankle joint

Bones and joints of the foot

Arches of the foot

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

Arch Formed by Supporting structures
Medial longitudinal arch
Lateral longitudinal arch
Transverse arch

Fascia and retinacula of the foot

Retinacula

Characteristics

Anterior retinacula

(Extensor retinacula)

Medial retinaculum

(Flexor retinaculum)

  • 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.
Lateral retinacula

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 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
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
  • 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
  • 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
Soleus
  • Head of fibula and middle 1/3rd of the medial border of the tibia (soleal line)
Plantaris
  • Lateral supracondylar line of the femur
  • 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
  • Hallux: flexion
  • Flex the hallux against resistance
Popliteus
  • 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
  • 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

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
  • Hallux: abduction
Flexor digitorum brevis
  • Lateral 4 toes: flexion at PIP joint
Abductor digiti minimi
  • 5th toe: abduction

Second layer

Quadratus plantae
  • Lateral 4 toes: flexion
Lumbricals
  • Extensor expansion of the lateral 4 toes
Third layer Flexor hallucis brevis
  • Base of the proximal phalanx of the hallux
  • Hallux: flexion at MTP
Adductor hallucis
  • Hallux: adduction
Flexor digiti minimi brevis
  • 5th toe: flexion at MTP
Fourth layer

Plantar interossei(3)

  • Medial side on the base of the proximal phalanges 3–5
  • Lateral 4 toes: adduction
Dorsal interossei (4)
  • 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, ∼ 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

Sole of the foot

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)

Small saphenous vein (SSV)

  • Origin: continuation of the lateral marginal vein of the foot (lateral end of the dorsal venous arch)
  • Course:
  • 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

Veins of the foot

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
  • 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)
  • 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 compartment 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