Lower Limb: Ankle and Foot

Lower Limb > Ankle and Foot > Study Aims
At the end of your study, you should be able to:
Understand the structure of the ankle mortise and its supporting ligaments and appreciate its vulnerability to injury
Know the bones of the foot and their organization
Understand the functional importance of the ligaments and fascia of the foot
Describe the arches of the foot
Understand the arrangement of the intrinsic muscles of the foot
Know the descriptive layers of the plantar surface of the foot

Pelvis and Perineum > Bones and Ligaments > Guides

7-5: Lower Limb: Ankle and Foot
    Ankle Joint (Talocrural Joint) (Plate 526 and Plate 527)
  • Uniaxial, synovial, hinge type joint
  • Articulation between tibia (medial malleolus), fibula (lateral malleolus), and talus
    • Distal ends of tibia and fibula form a mortise
    • Trochlea of talus fits into mortise
    • Malleoli grip talus
  • Movements
    • Dorsiflexion
      • Produced by muscles of anterior compartment of leg
      • Limited by triceps surae
      • More stable when dorsiflexed
    • Plantarflexion—produced by muscles of posterior compartment of leg
    • Some rotation, abduction, and adduction of joint possible in plantar flexion
  • Capsule
    • Thin
    • Supported by strong collateral ligament
    • Attached to tibia and malleoli superiorly and talus inferiorly
  • Ligaments:
    • Lateral consists of three parts
      • Anterior talofibular—from lateral malleolus to neck of talus
      • Posterior talofibular—from malleolar fossa to lateral tubercle of talus
      • Calcaneofibular—from tip of lateral malleolus to lateral calcaneus
    • Medial or deltoid
      • Strong ligament
      • Originates on medial malleolus
      • Fibers can be identified as
        • Anterior and posterior tibiotalar
        • Tibionavicular
        • Tibiocalcaneal
  • Blood supply: malleolar branches of fibular, and anterior and posterior tibial arteries
  • Nerve supply: Tibial nerve and deep fibular nerve (a branch of the common fibular)
Foot (Plate 523 and Plate 524)
  • 26 in number
  • Tarsal bones (7)
    • Talus
      • Has head, neck, body with trochlea, posterior, and lateral processes
      • Articulates with fibula, calcaneus, and navicular
      • Has no muscular attachments
      • Head rests on lateral projection of calcaneus—sustentaculum tali
      • Wider anteriorly making the ankle more stable in dorsiflexion
    • Calcaneus
      • Largest and strongest bone
      • Posterior prominence—calcaneal tuberosity—with medial, lateral, and anterior tubercles
      • Articulates with the talus and cuboid
      • Transmits body weight from talus to ground
      • Lateral projection—sustentaculum tali—supports talar head
    • Navicular
      • Flattened bone with inferomedial tuberosity
      • Located between talar head and three cuneiform bones
    • Cuboid
      • Inferolateral groove for tendon of peroneus longus
      • Most lateral bone in distal row of tarsals
    • Cuneiform (3)
      • Medial, intermediate and lateral
      • Each articulates with navicular posteriorly and base of related metatarsal anteriorly
      • Lateral articulates with cuboid
  • Metatarsals (5)
    • Have base (proximal), body, and head (distal)
    • Bases articulate with cuneiform and cuboid bones
    • Head articulate with proximal phalanges
    • Medial and lateral sesamoid bones on plantar surface of first metatarsal in plantar ligament
  • Phalanges (14)
    • Great toe (hallux) has two—proximal and distal
    • Other toes have three—proximal middle and distal
    • Each consists of proximal base, body, and distal head
  • Important intertarsal joints
    • Where inversion and eversion occur
    • Subtalar
      • Synovial joint with where talus rests on calcaneus
      • Fibrous capsule supported by talocalcaneal ligaments
    • Transverse tarsal, composed of
      • Calcaneocuboid joint
      • Talonavicular joint
  • Other joints where slight movement occurs
    • Talocalcaneal
    • Tarsometatarsal
    • Metatarsophalangeal (MTP)
    • Interphalangeal: proximal and distal (PIP and DIP)
  • Tarsal and metatarsal bones are arranged in longitudinal and transverse arches
  • Bony arches maintained by
    • Interlocking bones
    • Plantar ligaments
    • Plantar aponeurosis
    • Action of plantar muscles
  • Functions
    • Shock absorbers for body weight
    • Distribute body weight
    • Make foot adaptable to changes in surface
  • Longitudinal arch composed of medial and lateral arches
  • Medial longitudinal arch
    • Higher arch than lateral
    • Composed of calcaneus, talus, navicular, three cuneiforms, three medial metatarsals
    • Talar head is keystone
    • Strengthened by
      • Tibialis anterior tendon and attachments
      • Fibularis longus tendon
  • Lateral longitudinal arch
    • Flatter than medial
    • Rests on the ground when standing
    • Composed of calcaneus, cuboid, and lateral two metatarsals
  • Transverse arch
    • Formed by cuboid, cuneiforms, bases of metatarsals
    • Has pillars formed by lateral and medial longitudinal arches
    • Maintained by fibularis longus tendon
    Ligaments (major ligaments listed) (Plate 527)
  • All foot bones are united by plantar and dorsal ligaments
  • Plantar calcaneonavicular ligament
    • Also called spring ligament
    • From sustentaculum tali to navicular
    • Maintains longitudinal arch of foot
  • Long plantar ligament
    • From plantar surface of calcaneus to cuboid
    • Maintains foot arches
  • Plantar calcaneocuboid ligament
    • Also called short plantar ligament
    • Deep to the long plantar ligament
    • From inferior surface of calcaneus to inferior surface of cuboid.
    Plantar Muscles ( Table 7-5-1 for organization of layers and contents)
  • Four layers in the sole of the foot ( Plate 534) (Plate 533, Plate 535, and Plate 536)
  • Individual muscles of little importance as fine control of the toes is not required
  • A neurovascular plane exists between the first and second and third and fourth layers
    Dorsal Muscles of Foot
  • Form bulge on dorsolateral surface of foot, anterior to lateral malleolus
  • Two muscles blend together
  • Extensor digitorum brevis
    • Proximal attachment: superior surface, anterolateral calcaneus
    • Splits into four muscles, each with a tendon that blends with that of long extensor
    • One tendon to great toe
    • Other tendons to second to fourth toes
  • Extensor hallucis brevis
    • Largest and most medial belly of extensor digitorum brevis
    • Inserts on proximal phalanx of great toe
  • Supplied by deep fibular nerve
  • Assist extensor digitorum longus in extending toes
  • Deep fascia on dorsum of foot
    • Thin on dorsum
    • Continuous with inferior extensor retinaculum
    • Over lateral and posterior aspects it is continuous with plantar fascia
  • Deep fascia of plantar surface of foot
    • Central condensation of plantar fascia forms plantar aponeurosis
    • Arises from calcaneus
    • Divides into five fibrous bands that split to enclose digital tendons
    • Vertical septa from deep surface divide the foot into medial, central, and lateral compartments
  • Functions of plantar fascia
    • Holds foot together
    • Protects sole of foot from injury
    • Supports longitudinal arches
Lower Limb > Ankle and Foot > Figures
Plate 534: Lower LimbAnkle and FootMuscles of Sole of Foot: Second Layer
Lower Limb > Ankle and Foot > Tables

Table 7-5-1: Layers of plantar foot
Muscle Proximal Attachment Distal Attachment Action Innervation
First Layer—deep to plantar aponeurosis
Abductor hallucis Medial process of calcaneal tuberosity Medial side, base of proximal phalanx of first toe Abducts and flexes first toe Medial plantar nerve
Flexor digitorum brevis Medial process of calcaneal tuberosity Four tendons split to allow passage of long flexor tendons, insert on middle phalanges Flexes second through fifth toes Medial plantar nerve
Abductor digiti minimi Calcaneus Lateral side, proximal phalanx of fifth toe Abducts and flexes fifth toe Lateral plantar nerve
Neurovascular Plane: Medial and lateral plantar nerves
                         Medial and lateral plantar arteries and nerves
Second Layer
Quadratus plantae Medial and lateral sides of plantar surface of calcaneus Lateral edge of flexor digitorum longus tendon Corrects for oblique pull of FDL tendon; thus assists in flexion of toes Lateral plantar nerve
Lumbricals First: Medial side of tendon to second toe
Second through fourth: Adjacent sides of contiguous tendons
Medial side of dorsal digital expansions Flex proximal phalanges at MP joint, extend distal phalanges at PIP and DIP joints First (medial): Medial plantar nerve
Second through fourth: Lateral plantar nerve
Also: Tendon → tendons of flexor digitorum longus, tendon of flexor hallucis longus
Third Layer
Flexor hallucis brevis Plantar surfaces of cuboid and lateral cuneiform Divides in two, to each side of base of proximal phalanx of first toe Flexes proximal phalanx of first toe Medial plantar nerve
Adductor hallucis Oblique head: bases of second through fourth metatarsals
Transverse head: Ligaments of metatarsophalangeal joints
Lateral side, base of proximal phalanx of first toe (both heads) Adducts first toe, maintains transverse arch Deep branch of lateral plantar nerve
Flexor digiti minimi brevis Base of fifth metatarsal Base of proximal phalanx of fifth toe Flexes proximal phalanx of fifth toe Superficial branch, lateral plantar nerve
Neurovascular plane: Deep branches of lateral plantar nerve and artery; plantar arterial arch from lateral plantar artery
Fourth Layer
Plantar interossei (3) Bases and medial sides of third through fifth metatarsals Medial sides of bases of proximal phalanges of third through fifth toes Adduct second through fourth toes and flex MP joint Lateral plantar nerve
Dorsal interossei(4) Adjacent sides of first through fifth metatarsals First: medial side of proximal phalanx of second toe
Second through fourth: lateral sides of second through forth toes
Abduct second through fourth toes and flex MP joints Lateral plantar nerve
(Courtesy of Noelle Granger, PhD)

Lower Limb > Ankle and Foot > Facts and Hints

Box 7-5-1: Clinical Points
Ankle Sprain
  • As a result of tears in fibers of ligaments supporting the ankle
  • Commonly the result of forced inversion of foot causing strain on weaker lateral ligaments
  • Anterior talofibular ligament most likely to tear
  • Result in instability of ankle joint
  • Calcaneofibular ligament may also be torn
  • Box 7-5-2: Clinical Points
    Ankle Fracture
  • Severe ankle strain may fracture the medial, or more commonly, the lateral malleolus
  • A Pott's fracture-dislocation occurs when foot is forcefully everted, shearing off the medial malleolus
  • Lateral malleolus is then snapped as the talus moves laterally
  • May also fracture fibula above distal tibiofibular joint and distal end of tibia
  • Box 7-5-3: Clinical Points
    Plantar Fasciitis
  • Microtrauma to proximal attachment of the plantar aponeurosis to the calcaneus, resulting in inflammation of plantar aponeurosis
  • Caused by repetitive strain on the longitudinal plantar arch, such as during extensive running or high impact aerobics.
  • Pain felt over the proximal plantar surface of the foot
  • Especially painful after sitting and first thing in the morning
  • Treatment is conservative with rest and analgesia

    Box 7-5-4: Memory Aids
  • Structures travelling behind medial malleolus (anterior to posterior): Tom, Dick ANd Harry
    ibialis posterior flexor Digitorum longus flexor Hallucis longus AN= Posterior tibial Artery and tibial Nerve

  • Interossei muscles: Plantar interossei Adduct the digits (PAD) Dorsal interossei Abduct the digits (DAB)
  • Box 7-5-5: Memory Aids
  • Muscles that can potentially be absent in the body: 5 P's
  • Palmaris longus [Upper limb]
    Plantaris [Lower limb]
    Peroneus* [Lower limb]
    Pyramidalis [Anterior abdominal wall]
    Psoas minor [Posterior abdominal wall]
    * = peroneus (fibularis) tertius

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