Bio mechanics of Foot and ankle

INTRODUCTION
The foot and ankle form a complex system
which consists of: 28 bones
33 joints
112 ligaments
controlled by: 13 extrinsic muscles &
21 intrinsic muscles

CONT’D
The foot is sub divided into the:
rear foot
mid foot
fore foot
o It functions as a rigid structure for weight
bearing and it can also function as a flexible
structure to conform to uneven terrain

CONT’D
The foot and ankle provide various important
functions which include:
o Supporting body weight
o Providing balance
o Shock absorption
o Transferring ground reaction force
o Compensating for proximal mal alignment
o Substituting hand function in individuals with upper
extremity amputation/paralysis

BODY OF TALUS
MEDIAL [TIBIAL] FACET
HEAD OF TALUS
NAVICULAR
CUBOID
HEAD OF CALCANEUS
LATERAL [FIBULAR] FACET OF TALUS

TALOCRURAL JOINT
The talocrural joint is formed between the
distal tibia, fibula and talus and is
commonly known as "ANKLE JOINT"
The distal and inferior aspect of the tibia
known as- plafond, is connected to the
fibula via tibio-fibular ligaments, forming a
strong mortise which articulates with the
talar dome distally.
It is a hinge joint and allows dorsi flexion
& plantar flexion movements in the
“SAGITTAL PLANE”

TIBIA
CALCANEUS
TALUS
FIBULA
MEDIAL LATERAL

■ CAPSULE AND LIGAMENTS
 The capsule of the ankle joint is fairly thin and
especially weak anteriorly and posteriorly
 the stability of the ankle depends on an intact
ligamentous structure
 The ligaments that support the proximal and
distal tibio fibular joints (the crural tibiofibular
interosseous ligament, the anterior and posterior
tibiofibular ligaments, and the tibiofibular
interosseous membrane) are important for
stability of the mortise and, therefore, for stability
of the ankle.

CONT’D
Two other major ligaments maintain contact
and congruence of the mortise and talus and
control medial-lateral joint stability.
These are the MEDIAL COLLATERAL
LIGAMENT (MCL) and the LATERAL
COLLATERAL LIGAMENT (LCL).
The mcl most commonly called as
DELTOID LIGAMENT
The lcl is composed of 3 separate bands
that are commonly reffered to as separate
ligaments
These are anterior and posterior talo fibular
and calcaneo fibular ligaments

TALO CRURAL JOINT
The tip of the medial malleoli is anterior
and superior to lateral malleoli, which
makes its axis oblique to both the sagittal
and frontal planes.
The axis of rotation is approximately 13-
18° laterally from frontal plane and at an
angle of 8-10° from the transverse plane

CONT’D
Motion in other planes is required(like
horizontal and frontal plane) to achieve a
complete motion for plantar flexion and
dorsi flexion
The available range for dorsi flexion is: 0-30°
and plantar flexion range is: 0-55°

MOVEMENTS
Ankle joint
 dorsiflexion:
“raising the toes”
 plantarflexion:
“point the toes”

MUSCLES CAUSING MOVEMENT
 Tibialis anterior
 Peroneus tertius
 Extensor digitorum
longus
 Gastrocnemius
 Flexor digitorum longus
 Peroneus longus
 Plantaris
 Soleus
 Tibialis Posterior
DORSI FLEXORS PLANTAR FLEXORS

TIBIALIS ANTERIOR
 Origin Proximal 2/3 of
the lateral surface of the
tibia and interosseous
membrane
 Insertion Medial and
plantar aspects of the
medial cuneiform and the
base of the first
metatarsal
 Innervation Deep branch
of the peroneal n.
 Action Dorsiflexion,
inversion

PERONEUS TERTIUS
 Origin Distal 1/3 of the
medial surface of the fibula
and adjacent interosseous
membrane
 Insertion Dorsal surface
of the base of the 5th
metatarsal
 Innervation Deep
branch of the peroneal n.
 Action Dorsiflexion,
eversion

EXTENSOR DIGITORM LONGUS
 Origin Lateral condyle
of the tibia, proximal 2/3 of
the medial surface of the
fibula and adjacent
interosseous membrane
 Insertion Splits into 4
tendons that attach to the
proximal base of the dorsal
surface of the middle and
distal phalanges
 Action Extension of all
joints of toes 2-5 (MTP, PIP
and DIP joints)

EXTENSOR HALLUCIS LONGUS
 Origin Middle section of
the fibula and adjacent
 Insertion Dorsal base of the
distal phalanx of the great toe
 Action Extension of the
great toe, dorsiflexion

GASTROCNEMIUS
 Origin Medial head:
posterior aspect of the
medial femoral condyle
 Lateral head: posterior
aspect of the lateral femoral
condyle
 Insertion Calcaneal
tuberosity via the Achilles
tendon
 Innervation Tibial n.
 Action Plantar flexion,
flexion of the knee

SOLEUS
 Origin Proximal 1/3
of the posterior fibula
and fibular head and
posterior aspect of the
tibia
 Insertion Calcaneal
tuberosity via the
Achilles tendon
 Action Plantar flexion
of the foot at ankle

PLANTARIS
 Origin Lateral
supracondylar line of the
femur
 Insertion Medial aspect of
the Achilles tendon to insert
on the calcaneal tuberosity
initiates knee flexion

PERONEUS LONGUS
 Origin Lateral condyle
of the tibia, head and
proximal 2/3 of the lateral
surface of the fibula
 Insertion Lateral surface
of the medial cuneiform
and plantar base of the 1st
metatarsal
 Innervation
Superficial branch of
the peroneal n.
 Action eversion , plantar
flexion

TIBIALIS POSTERIOR
 Origin Proximal 2/3 of
the posterior aspect of
the tibia, fibula, and
 Insertion Multiple
attachments to every
tarsal except the talus,
also attaches to the
bases of metatarsals 2-4,
it’s the most prominent
insertion on the navicular
tuberosity
inversion

FLEXOR DIGITORUM LONGUS
 Origin Posterior surface of
the middle 1/3 of the tibia
 Insertion By 4 separate
tendons to the base of the
distal phalanx of the 4 lesser
toes
 Action Flexion of toes 2-
5, plantar flexion, inversion

FLEXOR HALLUCIS LONGUS
posterior fibula
 Insertion Plantar
surface of the base of
the distal phalanx of
the great toe
 Action Flexion of the
great toe, plantar
flexion, inversion

SUB TALAR JOINT
 It is also known as
the TALO
CALCANEAL JOINT
 It is formed between
the talus and
calcaneus
 The talus has three
facets[anterior,
middle, & posterior]
which articulate
inferiorly with
calcaneus

Facet of medial
malleolus
talus
calcaneus
Sustentaculum
talus
1st meta tarsal
sesamoid
Proximal phalanx
Distal phalanx
navicular
Medial cuneiform
Anterior subtalar
facet
Middle
subtalar
facet
Posterior
subtalar facet

SUB TALAR JOINT
 The axis of the sub
talar joint lies about
42° superiorly to the
sagittal plane and
about 16 to 23°
medial to the
transverse plane
 The literature
presents vast ranges
of sub talar motion
ranging from 5 to 65°

CONT’D
The average rom for pronation is 5° and
supination is 20°
Inversion and eversion rom has been
identified as 13° and 18° respectively
Total inversion and eversion motion is
about 2:1 (or) 3:2, ratio of inversion to
eversion movement

LIGAMENTS
 The subtalar joint is a
stable joint that rarely
dislocates.
 It receives ligamentous
support from the
ligamentous structures
that support the ankle, as
well as from ligamentous
structures that cross the
subtalar joint alone.
 The cervical ligament,
and the interosseous
talocalcaneal ligament.

2. SUB TALAR JOINT
Secondary to the anatomy of the sub talar
joint, the coupled motion of dorsiflexion,
abduction & eversion produces pronation
Where as the coupled motion of plantar
flexion, adduction & inversion produces
supination
It presents 2 point of articutalions anterior
talo calcaneal articulation & posterior talo
calcaneal articulation

CONT’D
During open kinematic chain inversion,
the calcaneus rolls into inversion & it
glides/ slide laterally
And during eversion, the calcaneus
rolls into evrsion & it glides/ slides
medially

MOVEMENTS
Subtalar
joint
 Calcaneal
inversion and
eversion

MUSCLES CAUSING MOVEMENT
 Tibialis anterior
 Tibialis posterior
 Flexor hallucis
longus
 Peroneus longus
 Peroneus brevis
 Peroneus tertius
 Extensor digitorum
longus
INVERTORS EVERTORS

PERONEUS BREVIS
lateral surface of the fibula
 Insertion Styloid process
of the 5th metatarsal
 Innervation Superficial
eversion

MID TARSAL JOINT
Also known as TRANSVERSE TARSAL JOINT/
CHOPARTS JOINT
It is an S shaped joint when viewed from
above and consists of 2 joints:
1. TALO NAVICULAR
2. CALCANEO CUBOID

TALO NAVICULAR JOINT
Formed between
the anterior talar
head and the
concavity on the
navicular
It does not have its
own capsule, but
rather shares one
with the two
anterior
talocalcaneal
articulations

CALCANEO CUBOID JOINT
Formed between the anterior facet of the
calcaneus and the posterior cuboid
Both articulating surfaces present a
convex and concave surface with the joint
Being convex vertically & concave
transversely very little movement occurs
at this joint

MID TARSAL JOINT
The mid tarsal joint rotates at two axes
due to its anatomy, making its motion
complex
Longitudinal axis lies about 15°
superior to the horizontal plane and
about 10° medial to longitudinal plane
Oblique axis lies about 52° superior to
the horizontal plane and 57° from mid
line

CONT’D
The longitudinal axis is close to the
sub talar joint axis and the oblique axis
is similar to the talo crural joint axis

TRANSVERSE TARSAL JOINT FUNCTION
 The subtalar and the transverse tarsal joints are
linked mechanically.
 Any weight-bearing subtalar motion includes talar
abduction/adduction and dorsiflexion/plantarflexion
that also causes motion at the talonavicular joint and
calcaneal inversion/eversion that causes motion at
the calcaneocuboid joint.
 Weight-bearing subtalar motion, therefore, must
involve the entire transverse tarsal joint.
 As the subtalar joint supinates, its linkage to the
Transverse tarsal joint causes both the talonavicular
joint and the calcaneocuboid joint to begin to
supinate also

MOVEMENTS
Supination
inversion
plantar flexion
adduction
Pronation
eversion
dorsiflexion
abduction

MT JOINT LOCKING
An important function of the foot is
propulsion of weight during stance
phase
This function is made possible by MT
joint locking and unlocking
During heel strike, the foot needs to be
flexible in order to adjust to the surface
and the MT joint unlocks to provide
this flexibility

CONT’D
Later in the gait cycle, the foot then needs to
act as a rigid lever to propel the weight of the
body forward which is made possible bymt
joint locking
During pronation/ eversion of the foot the
axis of the TN & CC joints are parallel to
each other, making it easier for them to
independently move and unlock the MT joint
The axes cross each other during
supination/inversion which locks the MT joint
making it difficult to move

CONT’D
Black wood et al concluded in the
study that there is incresed fore foot
movement when calcaneus is everted
This is consisted with the MT joint
locking mechanism

3.MID TARSAL JOINT
For TALO NAVICULAR joint the
concave navicular moves on convex
talus & hence the roll & glide is in the
same direction of movement
The CALCANEO CUBOID joint is a
saddle joint so the direction changes
depending on the movement

CONT’D
During flexion – extension the cuboid is
concave & the calcaneus is covex; hence
the roll and glide occurs in the same
direction as the talo navicular joint
During abduction – adduction, however
the cuboid is convex & calcaneus is
concave & therefore the roll & glide
occurs in the opposite direction

TARSO META TARSAL(TMT)
JOINT COMPLEX
Also known as LIS FRANC’S JOINT
The distal tarsal rows including the three
cuneiform bones and cuboid articulate with
the base of each metatarsal to form the TMT
complex
It is an plane synovial joint and is divided
into 3 distinct columns

CONT’D
MEDIAL – composed of 1st metatarsal and
medial cuneiform it has its own articular
capsule
MIDDLE - composed of 2nd and 3rd
metatarsals and lateral cunieforms
respectively
LATERAL – composed of 4th & 5th
metatarals and cuboid; it also divides the
mid foot from fore foot

LIS FRANC JOINT COMPLEX
The degree of sagittal motion for each TMT
joint is:
TMT JOINT DEGREE OF
MOTION
1st 1.6°
2nd 0.6°
3rd 3.5°
4th 9.6°
5th 10.2°

IP JOINT
MTP JOINT
TMT JOINT
BODY OF TALUS
TMT JOINT
MCP JOINT
PIP JOINT
DIP JOINT
AXIS OF 5TH RAY
AXIS OF 1ST RAY

TARSO METATARSAL JOINT FUNCTION
 The motions of the TMT joints are interdependent,
as are the motions of the CMC joints in the hand.
 Like the CMC joints of the hand, the TMT joints
contribute to hollowing and flattening of the foot.
 In weightbearing, the TMT joints function primarily
to augment the function of the transverse tarsal
joint;
 That is, the TMT joints attempt to regulate position
of the metatarsals and phalanges (the forefoot) in
relation to the weight-bearing surface.

4. LIS FRANC JOINT
Secondary to bony ligamentous anatomy of
the complex, its primary role is stability of
the mid foot & has a very little movement
It has 3 distinct arches & the main stabilizing
structure of TMT joint is a Y shaped
ligament known as LISFRANC’S
LIGAMENT

DORSI
FLEXION
PLANTAR
FLEXION
FIRST RAY INVERSION AND
SLIGHTLY ADDUCTION
EVERSION AND SLIGHT
ABDUCTION
SECOND RAY SLIGHT INVERSION SLIGHT EVERSION
THIRD RAY -------- --------
FOURTH RAY SLIGHT EVERSION SLIGHT INVERSION
FIFTH RAY EVERSION , SLIGHT
ABDUCTION
INVERSION , SLIGHT
ADDUCTION

SUPINATION TWIST
 When the hind foot pronates to any substantial
degree the transverse tarsal joint generally
supinate to countervrotate the foot
 The first and second ray will be pushedinto
dorsiflexion by the ground reaction force, and the
muscles controlling the fourth and fifth rays will
plantarflex
 The TMT joints in an attempt to maintain contact
with the ground.

CONT,D
 Both dorsiflexion of the first andsecond rays
and plantarflexion of the fourth and fifthrays
include the component motion of inversion
of the ray.
 Consequently, the entire forefoot (each ray
and its associated toe) undergoes an
inversion rotation around a hypothetical axis
at the second ray
 This rotation is referred to as supination
twist of the TMT joints

PRONATION TWIST
When both the hindfoot and the transverse
tarsal joints are locked in supination, the
adjustment of forefoot position must be left
entirely to the TMT joints.
 With hindfoot supination, the forefoot tends
to lift off the ground on its medial side and
press into the ground on its lateral side.

CONT,D
 The muscles controlling the first and second
rays will cause the rays to plantarflex in
order to maintain contact with the ground,
whereas the fourth and fifth rays are forced
into dorsiflexion by the ground reaction
force.
 Because eversion accompanies both
plantarflexion of the first and second rays
and dorsiflexion of the fourth and fifth rays,
the forefoot as a whole undergoes a
pronation twist

META TARSO PHALANGEAL(MTP) &
INTER PHALANGEAL(IP) JOINTS
The MTP joints are formed between the
meta tarsal heads and the corresponding
bases of the proximal phalanx
The inter phalangeal joints of the toes are
formed between the phalanges of the toes
Each toe has proximal and distal IP joints
except for the great toe which only has one
IP joint

MTP AND IP JOINTS
The MTP joints are bi axial & move in sagittal
and transverse planes. MTP joints have a
greater sagittal plane movement and very
little transverse plane movement
At the MTP joints, hyper extension is about
90° & flexion is about 30 to 45°.
IP joints are hinge joints which limit motion in
one direction

METATARSOPHALANGEAL JOINT FUNCTION
 The MTP joints have two degrees of freedom,
 But flexion/extension motion is much greater than
abduction/adduction motion, and extension
exceeds flexion.
 Although MTP motions can occur in weight-
bearing or non–weight-bearing,
 The MTP joints serve primarily to allow the
weight-bearing foot to rotate over the toes through
MTP extension (known as the metatarsal break)
when rising on the toes or during walking

MTP & IP JOINTS
Glide and roll is in the same direction as the
movement for the MTP joints as the concave
base of the phalanx moves on the convex
head of metatarsal
The same is true for the IP joints where glide
& roll is in the same direction as the concave
distal convex moves on the convex proximal
phalanx

IP JOINT FUNCTION
 The interphalangeal (IP) joints of the toes
are synovial hinge joints with one degree of
freedom: flexion/Extension
 The toes function to smooth the weight shift
to the opposite foot in gait and help maintain
stability by pressing against the ground in
standing.

INTRINSIC MUSCLES OF THE FOOT
 Flexor digitorum brevis
 ABDuctor Hallucis
 ABDuctor digiti minimi
 Dorsal interossei
(ABDuctors)
 Plantar interossei
(ADDuctors)
 Lumbricals
 Flexor Hallucis Brevis
 ADDuctor Hallucis
 Extensor Digiti Minimi

JOINT TYPE OF
JOINT
PLANE OF
MOVEMENT
MOTION
TC JOINT HINGE SAGITTAL DORSI &
PLANTAR
FLEXION
ST JOINT CONDYLOID MAINLY
TRANSVERSE,
SOME SAGITTAAL
INVERSION &
EVERSION
DF & PF
MT JOINT TN-BALL&SOCKET
CC-MODIFIED
SADDLE
LARGRLY IN
TRANSVERSE,
SOME SAGITTAL
INVERSION &
EVERSION
FLEX & EXT
TMT JOINT PLANAR
MTP JOINT CONDYLOID SAGITTAL SOME
TRANSVERSE
FLEX & EXT
ABD & ADD
IP JOINT HINGE SAGITTAL FLEXION &
EXTENSION

PRIME MOVERS
 Action Muscle
 Plantarflexion Gastrocnemius, soleus
 Dorsiflexion Tibialis anterior
 Inversion Tibialis anterior, tibialis posterior
 Eversion Peroneus longus, peroneus brevis
 Flexion of hallux Flexor hallucis longus
 Flexion of toes 2-5 Flexor digitorum longus
 Extension of hallux Extensor hallucis longus
 Extension of toes 2-5 Extensor digitorum longus

INFLUENCE OF KINETIC
CHAIN
As discussed above with MT joint locking
the transition of foot from pronation to
supination is an important function that
assist in adapting to uneven terrain & acting
as a rigid lever during push off
During pronation, MT joint unlocks providing
flexibility of the foot & assists in maintaining
balance
During supination, MT joint locks providing
rigidity of the foot & maximizing stabilty

CONT’D
If the foot stucked pronated, this would lead to
hyper mobility of the mid foot and placing
greater demand on the neuromuscular
structure stabilize foot and maintaining upright
stance
Whereas if foot is stucked supinated the mid
foot would be hypo mobile which would
compensate the ability of the foot to adjust to
the terrain and increasing demand on the
surrounding sructure to maintain postural
stability and balance

CONT’D
Cote etal concluded that postural stability is
affected by positioning under static and
dynamic conditions
Chain reaction occurs secondary to the
positioning of foot

CONT’D
In closed chain movement following
kinetic reaction with over pronated foot
takes place
 Calcaneal eversion
 Adduction & plantar flexion of talus
 Medial rotation of talus
 Medial rotation of tibia & fibula
 Valgus at knee
 Medial rotation of femur
 Anterior tilting of pelvis

CONT’D
In closed chain movement following
kinetic chain reaction with over
supinated foot takes place
 Calcaneal inversion
 Abduction & dorsiflexion of talus
 Lateral rotation of tibia & fibula
 Varus at knee
 Lateral rotation of femur
 Posterior tilting of pelvis

The arches of foot provide functions of force
absorption,base of support and acts as a
rigid lever during gait propulsion
The 3 arches of the foot are:
Medial longitudinal arch
Lateral longitudinal arch
Transverse arch

MEDIAL LONGITUDINAL ARCH
It is the longest & highest of all the arches
Bony components of MLA include
calcaneus, talus, navicular, & 3 cunieform
bones & 1st 3 meta tarsal
Consists of 2 pillars:
ANTERIOR PILLAR: consists of 3 meta
tarsal heads
POSTERIOR PILLAR: consists of tuberosity
of calcaneus
Plantar apponeurosis forms the supporting
beam connecting the 2 pillars

CONT’D
Apex of MLA is superior articular surface of
talus
In addition to plantar apponeurosis the MLA
is supported by SPRING LIGAMENT &
DELTOID LIGAMENT
Tibialis anterior and posterior muscles play
an important role in raising the medial border
of the arch
Flexor hallucis longus acts as a bow string

LATERAL LONGITUDINAL ARCH
It is the lowest arch & comprises of
calcaneus, cuboid & 4th & 5th metatarsal as
its bony component
Like MLA the posterior pillar consists of
tuberosity of calcaneus
Anterior pillar is formed by meta tarsal
heads of 4th & 5th meta tarsals

CONT’D
Plantar apponeurosis and long & short
plantar ligaments provide support for LLA
Peroneus longus tendon play an important
role in maintaining the lateral border of the
arch

TRANSVERSE ARCH
It is concave in non weight bearing which
runs medial to lateral in mid tarsal & tarso
meta tarsal area
The bony component of the arch consists of
meta tarsal heads, cuboids and 3 cunieform
bones
The medial and lateral pillar of the arch is
formed by medial and lateral longitudinal
arch

CONT’D
The arch is maintained by posterior tibialis
tendon and peroneus longus tendon
Cross the plantar surface from medial to
lateral and lateral to medial respectively

WINDLASS MECHANISM
The plantar aponeurosis acts similarly as
windlass mechanism
Windlass is typically a horizontal cylinder
that rotates with a crank or belt on a chain
or rope to pull a heavy object
Common use of windlass is seen in pulling
the anchor of ship known as anchor
windlass
This mechanism can be seen in foot

CONT’D
When the mtp joints are hyper extended,
the plantar aponeurosis becomes taut as it
is wrapped around the mtp joints
This action brings the meta tarsal and tarsal
bones together converting it into a rigid
structure and eventually causing the
longitudinal arches to raise
This function is important in providing a rigid
lever for gait propulsion during push off

Bio mechanics of Foot and ankle

Bio mechanics of Foot and ankle

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