Lower limb anatomy (Foot, ankle and rib/fib)

Question 1

tibia/fibula bones and muscles divided into three compartments:

Answer 1

Anterior
Lateral
Posterior

Question 2

tibia

Answer 2

Larger and stronger than fibula
Weight-bearing

Triangular in cross-section, apex anterior
Numerous muscle attachments

Tibial condyles/plateau proximally
Distal tibia flattened (plafond) to articulate with talus
medial tubercle (malleolus)

Question 3

fibula

Answer 3

Thinner and weaker than tibia

Non-weight-bearing

Important muscle attachment site, completely enclosed

Enlarged distal end (malleolus) longer than tibial malleolus

Question 4

Tibia/fibula articulations

Answer 4

Form a bony ring

Proximal tibio-fibular joint (synovial)

Inter-osseous membrane:
fibrous connective tissue
Increases area for muscle attachment
Openings for nv vessels

Distal tibio-fibula joint
Fibrous joint (syndesmosis)
Thickening of membrane with anterior/posterior tibio-fibular ligaments
Integral to strength of ankle

Question 5

Muscle compartments

Answer 5

Posterior:
Deep/superficial
Action:
Plantar-flex foot
Flex toes
Invert (medially rotate) foot
Achilles tendon

Lateral:
Peroneus longus/brevis
Evert (externally rotate) foot

Anterior compartment:
Four muscles
Action:
Dorsi-flex foot
Extend toes
Invert foot

Each enclosed by fascia and has own nv bundles; compartment syndrome

Question 6

Foot

Answer 6

Equivalent to hand/wrist

Divided into:
Phalanges (14)
Metatarsals (5)
Tarsals (7)

Can also be divided as:
Forefoot
Midfoot
Hindfoot

Dorsal / plantar surfaces

Numerous and variable accessory ossicles

Question 7

Phalanges/toes

Answer 7

Hallux and 2nd-5th toes

2 in hallux (great toe)
3 in other digits (proximal, middle, distal)

Each has BASE, shaft, head

Separated by interphalangeal joints

Question 8

Metatarsals

Answer 8

Numbered 1-5

1st is shortest and strongest
2nd longest

Base, shaft, head/neck

Articulates distally at metatarso-phalangeal joints
Proximally at tarso-metatarsal (lisfranc) joints with adjacent metatarsals and tarsals

Sesamoid bones

Question 9

Mid foot/distal tarsals

Answer 9

Navicular (boat)

Cuneiforms (wedge)
Medial
Intermediate
Lateral

Cuboid (cube)

Question 10

hindfoot

Answer 10

Separated from mid foot (navicular/cuboid) by chopart joints

TaLUS (ankle) articulates with tibia/fibula

Calcaneum (HEEL)

Best visualised with ankle projections

Question 11

calcaneum

Answer 11

short bone forms major weight-bearing portion of foot
Commonly fractured in falls from height

Multiple tuberosities / articular surfaces:
Calcaneal tuberosity and process
Anterior/posterior articular surface (sub-talar joint)
Sustentaculum tali (horizontal shelf of bone)
Anterior process
Peroneal (fibular) tubercle

Question 12

talus

Answer 12

Formed of three parts:
head (distal)
Neck
Body

body articulates with tibia/fibula, almost entirely covered by hyaline cartilage (talar dome)
Inferior articular facets correspond with calcaneum facets to form sub-talar joint
Narrowing of neck forms tarsal sinus with calcaneal sulcus

Interesting features:
Majority covered in hyaline cartilage (60%)
No muscular/tendinous attachments
Prone to avascular necrosis in fractures due to arterial supply through neck

Fractures known as aviator’s

Question 13

Ossification centres (Fore/midfoot

Answer 13

Phalanges:
Primary: diaphysis/shaft (9-15th week in utero)
Secondary: proximal epiphysis/base only (2-8years)
Fuse by 18 years

Metatarsal:
Primary: diaphysis/shaft (9-10th week in utero)
Secondary:
Base/proximal epiphysis hallux (3 years)
Heads/distal epiphysis 2-5th metatarsals (3-4 years)
Base 5th metatarsal apophysis
Fuse 17-20 years

Tarsals
Primary:
Calcaneum (3-4 month in utero)
Talus (6 month in utero)
Cuboid (9th week in utero)
Lateral cuneiform (1 year)
Medial cuneiform (2 years)
Intermediate cuneiform (3 years)

Question 14

Ankle joint

Answer 14

Synovial saddle joint
Dorsi/plantar-flexion of the foot
Other movements through other joints
Referred to as the mortise joint
Formed by:
Tibial plafond superiorly
Lateral malleolus
Medial malleolus
Talar dome
Joint more stable with foot in dorsi-flexion (important in posistioning)

Question 15

Ossification centres (ANKLE/HINDFOoT)

Answer 15

Distal Tibia:
Primary: diaphysis/shaft (7th week in utero)
Secondary Distal epiphysis/medial malleolus (1 year)
Fuses 15-17 years

Distal fibula:
Primary: diaphysis/shaft (8th week in utero)
Secondary Distal epiphysis/medial malleolus (1 year)
Fuses 17-19 years

Secondary:
Calcaneum:
posterior surface (6-8 years).
Fuses at puberty
Talus:
occasionally has posterior process
os trigonum if un-united by maturity
Normal variant

Question 16

Ankle joint

Answer 16

Surrounded by synovial membrane and fibrous capsule

Ligamentous structures provide large amount of strength/stability

Generally named by structures they connect

Tibio-fibular syndesmosis
Medial (deltoid)
fan-shaped
4 parts
Lateral
3 parts

Bony ring theory; injuries often a combination of bony/soft tissue abnormalities
Think about forces involved

Question 17

Inter-tarsal joints

Answer 17

Remaining movements produced by smaller joint in the midfoot:
Inversion / eversion
Supination/pronation

Predominantly of:
Sub-talar
Talocalcaneonavicular
Calcaneocuboid

Synovial, supported by extensive ligamentous complex

Question 18

Other joints

Answer 18

Tarso-metatarsal (TMT)
Lisfranc joints / ligaments
Synovial plane joints
Sliding movement to allow pronation/supination
Greatest of 1st tmt joint

Metatarso-phalangeal (MTPJ)
Synovial ellipsoid
Flexion/extension
Some other movements
Supported by ligament complex

Interphalangeal joints
Hinge
Flexion/extension

Question 19

Arches of the foot

Answer 19

Help to distribute great forces on the foot

Longitudinal arch
Calcaneum to metatarsal heads
Most pronounced medially
Supported by plantar fascia/aponeurosis

Transverse arch

Supported by soft tissue anatomy

Foot problems intrinsically linked to biomechanics of the anatomy; wide range of causes

Question 20

musculature

Answer 20

Extensive and complex (especially plantar surface), major components include:

Intrinsic (arise in foot)
Extrinsic (arise in leg)

Extensors (dorsal)
Flexors (Plantar)

Question 21

Neurovascular supply

Answer 21

Supplied either:

Dorsally alongside extensor tendons
Anterior tibial/dorsalis pedis artery
Fibular nerves
great saphenous vein

Through tarsal tunnel medially
Posterior to medial malleolus
Posterior tibial artery (can palpate pulse)
Tibial nerve
Small saphenous vein