The document summarizes the biomechanics of the ankle joint complex. It describes the anatomy and function of the talocrural joint (ankle joint), subtalar joint, and transverse tarsal joint. The ankle-foot complex consists of 28 bones and 25 joints that allow the foot to meet stability and mobility demands through dorsiflexion, plantarflexion, pronation, and supination movements. Key bones include the talus, tibia, and fibula. Ligaments such as the deltoid and tibiofibular ligaments provide stability to the ankle mortise.

1. Biomechanics of ankle joint

2. Ankle-FOOT COMPLEX
• The ankle-foot complex is structurally
analogues to the wrist-hand complex of the
upper extremity.
• The ankle-foot complex must meet the
stability and mobility demands.
Stability demands-
1.Providing a stable base of support for the
body in a variety of weight bearing postures
without undue muscular activity and energy
expenditure.
2.Acting as a lever for effective push-off during
gait.

3. Mobility demands-
1.Dampening of rotations imposed by more
proximal joints of LL.
2.Being flexible enough as a shock absorber
3.Permitting the foot to conform to the changing
and varied terrain on which foot is placed.

4. • The ankle and foot meet its requirements through
• 28 bones
• 25 joints.
These include
 proximal and distal tibiofibular joints
 Talo-crural or ankle joint
 Talocalcaneal or subtalar joint
 Talonavicular joint
 Calcaneocuboid joint
 5 tarso-metatarsal joints
 5 metatarso-phalangeal joints
 9 inter-phalangeal joints

6. • The bones of the foot are traditionally divided
into 3 functional segments.
• HIND FOOT-posterior segment
composed of talus and calcaneus
• MID FOOT-middle segment
composed of navicular,cuboid, 3 cuneiforms
• FOREFOOT-anterior segment
composed of metatarsals and phalanges.

7. ANKLE JOINT
The term ankle specifically refers to :
• Talocrural joint-The formation of the mortise
(a hole) by the medial malleoli (Tibia) and
lateral malleoli (fibula) with the talus lying
in between them makes up the talocrural
joint.
• The ankle is a synovial Hinge joint with
joint capsule and associated ligaments.
• It is generally considered to have a single
oblique axis with 1°of freedom.

8. PROXIMAL ARTICULAR STRUCTURE
• The proximal segment of ankle is composed of
concave surface of distal tibia and of tibial and
fibular malleoli.
• The structure of distal tibia and the two
malleoli is referred to as a MORITSE.
• The mortise of the ankle is adjustable, relying
on the proximal and distal tibio-fibular joints.

9. PROXIMAL TIBIO-FIBULAR JOINT
• It is a plane synovial joint formed by
articulation of head of fibula with the postero-
lateral aspect of tibia.
• Although facets are flat, a slight convexity of
tibial facet and slight concavity of fibula is
predominant.
• Each proximal tibiofibular joint is surrounded
by a joint capsule that is reinforced by
anterior and posterior tibiofibular ligaments.

10. DISTAL TIBIOFIBULAR JOINT
• It is a syndesmosis or fibrous union.
• It is in between the concave facet of tibia and
convex facet of fibula.
• Tibia and fibula do not come into contact with
each other at this point but are separated by
fibro-adipose tissue.
• The ligaments of distal tibio-fibular joint are
primarily responsible for maintaining a stable
mortise.

12. Talocrural joint
Talus
Tibia
Fibula
<<<Talocrural joint

13. Ligaments
 Crural tibio-fibular interosseous ligament
 Anterior and posterior tibiofibular ligaments
 Interosseous membrane.

14. Anterior view
Anterior talo-fibular lig
Anterior tibio-fibular lig
talus
Tibia
Fibula

15. Distal articular surface
TALUS
3 Articular Surfaces
• Larger lateral facet-triangular shaped
• Smaller medial facet-comma shaped
• Superior facet- TROCHLEAR

17. ligaments
• Fibrous capsule
• Deltoid or medial ligament- strong
triangular
Superficial part
Deep part
Superficial part-
ANTERIOR TIBIONAVICULAR
MIDDLE TIBIOCALCANEAN
POSTERIOR TIBIOTALAR

18. Medial view
<Deltoid lig
<Tibialis Ant. Tendon
<Tibialis Posterior Tendon
<Navicular
Talus
<Tibia

19. Deep Part
It is also called as Anterior tibio-talar
ligament.
Attached to the anterior part of medial surface
of talus.
• Lateral ligament
It consists of 3 bands
Anterior talofibular ligament
Posterior talofibular ligament
Calcaneofibular ligament

20. Lateral view
Posterior tibio-fibular >
<Ant talo fibular
< calcaneofibular
<Peroneal tendonscalcaneus
<Sub talar joint space
Fibula

21. Posterior view
<Achillies tendon
<Posterior talo-fibular
<Posterior tibio-fibular

22. Ankle joint function
• The primary ankle motion of dorsi-flexion
and plantar-flexion occurs around an
oblique axis that causes the foot to move
across all 3 planes.
AXIS
• In neutral position of the ankle, the joint
axis passes approximately through the
fibular malleolus and the body of the talus
and through or just below the tibial
malleolus and posteriorly.

23. Talar
rotation(7
° med and
10° lat
rotation)
Abduction
-
adduction
Transvers
e plane
Vertical
axis
Talar
tilt(5°)
Inversion-
eversion
Frontal
plane
Anteropos
terior axis
Dorsiflexi
on-
plantar
flexion
Antero-
posterior
plane
Frontal
axis
•Supination = PF + Adduction + Inversion
• Pronation = DF + Abduction + Eversion

25. • The distal tibia is twisted laterally compared
with its proximal portion accounting for toe-out
position of the foot in normal standing.
• The axis of angle is considered to be rotated
laterally 20°-30° in the transverse plane and
inclined 10° down on the lateral side.

26. Movements

27. ARTHROKINEMATICS
• The shape of the body of talus is complex.
• The trochlea is wider anteriorly than
posteriorly.
• The lateral (fibular) facet is substantially larger
than the medial (tibial) facet and its surface is
oriented slightly obliquely to that of medial
facet.
• This resembles a truncated cone.
• This causes greater displacement of fibular
malleolus on lateral facet of talus than the
tibial on medial facet.

28. • The greater excursion of the lateral malleollus
results in the imposition of motion on the fibula
in several directions through the ankle ROM.
• This motion is found to be small in magnitude
and variable in direction among individuals and
with different loading conditions.
• This is related to the orientation of the proximal
tibiofibular facet,with more mobility available in
those facets that are more vertical.
• It may depend on the tibiofibular ligamentous
elasticity.

29. Dorsiflexion
peroneus tertius
(usually very
close to extensor
digitorum longus
and often
considered as
part of this muscle)
tibialis
anterior
extensor
digitorum
longus
extensor
hallucis
longus
(deep to ext.
digitorum
longus)

30. Plantar Flexors
NOTE:
1) Soleus
lies
deep to
gastrocnem
ius
2) Both
insert into
the
calcaneal
tendon aka
Achilles
tendon
SoleusGastrocnemius
Posterior View

31. tibialis
anterior
extensor
hallucis
longus
flexor
digitorum
longus
flexor
hallucis
longus
tibialis
posterio
r
Invertors
primary
NOTE: Muscles pass
to the medial side of
the foot!

32. peroneus
brevis
peroneus
longus
peroneus
tertius
extensor
digitorum
longus
Evertors
primary

33. Subtalar joint
• The talocalcaneal or subtalar joint is a
composite joint formed by three separate plane
articulations between the talus superiorly and
calcaneus inferiorly.
• Provides a triplanar movement around a single
joint axis.
Articulations
posterior talocalcaneal articulations-Largest
concave facet-undersurface of body of talus
convex facet- calcaneus

34. • Anterior and medial talocalcaneal articulations
Convex facet- Inferior body and neck of talus
respectively
Concave facet-calcaneus
• Between the posterior articulation and
anterior,middle articulation a bony tunnel is
present formed by a sulcus(concave groove) in
the inferior talus and superior calcaneus.
• This funnel shaped tunnel is called TARSAL
CANAL

37. • TARSAL CANAL
Larger end- SINUS TARSI-lies anterior to fibular
malleolus
smaller end- lies posterior to the tibial
malleolus.
And above a bony out cropping on calcaneus is
called SUSTENTACULUM TALI
Posterior articulation has its own capsule
Anterior and middle articulations share a
capsule with the talonavicular joint.

38. • Ligaments
Cervical ligament- strongest
Interosseus talocalcaneal ligament
anterior band
posterior band
Others-
Calcaneofibular lig
lateral talocalcaneal lig
Inferior extensor retinaculum –provides subtalar
support
Cervical,interosseus,collaterals-talocalcaneal
stability

40. Subtalar Joint
• Allow pronation/supination
and rotation.
• The talus articulates with
the calcaneus anteriorly,
posteriorly and medially.
• The axis of rotation runs
diagonally from the
posterior, lateral, plantar
surface to the anterior,
medial, dorsal surface.
• The orientation of this axis
makes pronation/supination
triplanar with reference to
the cardinal planes.

41. COMPONENT MOVEMENTS
NON- WT BEARING WT-BEARING
SUPINATION CALCANEAL
INVERSION(VALGUS)
CALCANEAL
INVERSION(VARUS)
CALCANEAL
ADDUCTION
TALAR ABDUCTION
(LATERAL ROTATION)
CALCANEAL
PLANTAR FLEXION
TALAR
DORSI-FLEXION
TIBIOFIBULAR LAT
ROT

42. NON-WT BEARING WT-BEARING
PRONATION CALCANEAL
EVERSION(VALGUS)
CALCANEAL
EVERSION(VALGUS)
CALCANEAL
ABDUCTION
TALAR ADDUCTION
(MEDIAL ROT)
CALCANEAL DORSI-
FLEXION
TALAR PLANTAR-
FLEXION
TIBIO-FIBULAR
MEDIAL ROTATION

43. Tibial Rotation• The subtalar joint can be
likened to the action of a
mitered hinge (Inman and
Mann, 1973).
• The orientation of the
subtalar joint axis causes
the tibia to internally rotate
during pronation and
externally rotate during
supination.
• Thus, the tibia internally
rotates with pronation or
knee flexion and externally
rotates with supination or
knee extension.
It is important that
knee flexion and
pronation occur in
synchronization (as
well as knee-extension
and supination).

44. • CLOSED PACKED POSITION-
FULL SUPINATION
• POSITION OF RELATIVE MOBILITY –
PRONATION

45. Transverse tarsal joint
• The transverse tarsal joint, also called the
midtarsal or Chopart joint
It is a compound joint formed by the
talonavicular and calcaneocuboid joints .
• The two joints together present an S-
shaped joint line that transects the foot
horizontally, dividing the hindfoot from the
midfoot and forefoot.
• The navicular and the cuboid bones are
considered, immobile in the weight-bearing
foot.

47. • Talonavicular joint
• The proximal portion of the talonavicular
articulation is formed by the anterior portion
of the head of the talus, and the distal
portion of the articulation, by the
concave posterior aspect of the navicular
bone.
• A single joint capsule encompasses the
talonavicular joint facets and the anterior
and medial facets of the subtalar joint.

48. • Ligaments
• Inferior aspect of the joint capsule-
plantar calcaneo-navicular lig/spring lig
• Medially- deltoid lig
• Laterally-bifurcate lig

50. • Calcaneo-cuboid joint
• The calcaneo-cuboid joint is formed
proximally by the anterior calcaneus and
distally by the posterior cuboid bone
• The calcaneocuboid articulation has its own
capsule that is reinforced by several
important ligaments.
The capsule is reinforced
• Laterally - lateral band of the bifurcate
ligament (also known as the calcaneocuboid
ligament)

51. • Dorsally –dorsal calcaneocuboid ligament,
• Inferiorly -plantar calcaneocuboid (short
plantar) and the long plantar ligaments

52. Midtarsal Joint
Actually consists of two joints: the
calcaneocuboid on the lateral side
and the talonavicular on the medial
During pronation,
the axes of these
two joints are
parallel, this unlocks
the joint and creates
a hypermobile foot
that can absorb
shock.
During supination the
axes are not parallel
and this joint
becomes locked
allowing efficient
transmission of
forces.

53. Tarsal transverse joint axis
• The transverse joint is considered to have two
axis around which the talus and calcaneus
moves on the relatively fixed naviculo-cubiod
unit.
LONGUTUDINAL AXIS
OBLIQUE AXIS
Longitudinal axis-
• Motion around this axis is triplanar
producing supinaion /pronation with
coupled components similar to those seen in
subtalar joint.
• It approaches a true A-P axis producing
inversion and eversion component
predominate.

54. The longitudinal axis of the transverse
tarsal joint
Inclined 15° superiorly from the transverse plane
15°

55. Inclined 9° medially
from the sagittal plane.
9°

56. • Oblique axis
• This triplanar axis also provides
supination/pronation with coupled component
movements of the talus and calcaneus segments
moving together on the navicular and cuboid
bones.
• The dorsiflexion/plantarflexion and
abduction/adduction components predominate
over inversion/eversion
motions.
• Motions about the longitudinal and oblique axes
are difficult to separate and quantify.

57. The oblique axis of the
transverse tarsal
joint .
Inclined 57° from the
sagittal plane57°

58. Inclined 52°
superiorly from the transverse plane.
52°

59. TRANSVERSE TARSAL JOINT
FUNCTION
• Any weight-bearing subtalar motion
includes talar abduction/adduction-
dorsiflexion/plantarflexion that also causes
motion at the talonavicular joint
• calcaneal inversion/eversion that causes
motion at the calcaneocuboid 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.(CLOSE PACKED POSITION)

60. • When the subtalar joint is pronated and
loose-packed, the transverse tarsal joint is
also mobile and LOOSE PACKED .
• The transverse tarsal joint is the
transitional link between the hindfoot and
the forefoot, serving to
(1)add to the supination/pronation range of
the subtalar joint and
(2) compensate the forefoot for hindfoot
position.

61. • Weight-Bearing Hindfoot Pronation and
Transverse Tarsal Joint Motion
In the weight-bearing position, medial rotation
of the tibia
for example-pivoting on a fixed foot
• Weight-Bearing Hindfoot Supination and
Transverse Tarsal Joint Motion
• A lateral rotatory force on the leg will create
• subtalar supination in the weight-bearing
subtalar joint with a relative pronation of the
transverse tarsal joint (opposite motion of the
forefoot segment) to maintain appropriate

62. weight-bearing on a level surface Supination
of the subtalar joint, however, can proceed
to only a certain point before the transverse
tarsal joint also begins to supinate.

63. PRONATION
With pronation occurring at the subtalar joint through medial rotation
of the leg, the transverse tarsal joint is free to
(A) supinate slightly to maintain the relatively fixed position of the
forefoot segment; (B) pronate slightly as occurs in normal
standing; or
(C)supinate substantially to maintain appropriate weight-bearing of
the forefoot segment on uneven terrain

64. SUPINATION
With supination occurring at the subtalar joint through lateral
rotation of the leg, the transverse tarsal joint has limited ability to
pronate to maintain the relatively fixed position of the forefoot
segment
(A); will begin to supinate with a greater range of
subtalarsupination and lateral rotation of the leg (B); or will fully
supinate along with a fully supinated subtalar joint and maximal
lateral rotation of the superimposed leg (C).

65. TARSOMETATARSAL
JOINTS• The tarsometatarsal TMT joints are plane
synovial joints formed by the distal row of tarsal
bones (posteriorly) and the bases of the
metatarsals.
• LIGAMENT
Deep transverse metatarsal ligament
• This spans the heads of the metatarsals on the
plantar surface and is similar to that found in
the hand.
• Contribute to stability of proximal located TMT
joints by preventing excessive motion and
splaying of metatarsal heads.

66. • Axis
• A ray is defined as a functional unit formed
by a metatarsal and (for the first through
third rays) its associated cuneiform bone.
• The cuneiform bones are included as parts
of the movement units of the TMT rays
because of the small and relatively
insignificant amount of motion occuring at
the cuneonavicular joints.

67. • The axis of the first ray is inclined in such as
way that dorsiflexion of the first ray also
includes inversion and adduction, whereas
plantarflexion is accompanied by eversion and
abduction.
• The abduction/adduction components normally
are minimal.
• Movements of the fifth ray around its axis are
more restricted and occur with the opposite
arrangement of components.
• Dorsiflexion is accompanied by eversion and
abduction, and plantarflexion is accompanied

68. by inversion and adduction.
• The axis for the third ray nearly coincides
with a coronal axis; the predominant
motion, therefore, is
dorsiflexion/plantarflexion.
• The axes for the second and fourth rays
were not determined

70. • FUNCTION
• 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.

71. • SUPINATION TWIST
• When the hind foot pronates substantially in
wt-bearing position.
• The TTJ Joint counter acts the forefoot to
keep the plantar aspect of the foot in contact
with the ground.
• TMT –medial forefoor will press the ground
lateral foot will lift off the ground
1st and 2nd ray -dorsiflexion
4th and 5th ray-plantarflexion

72. • the entire forefoot undergoes an inversion
rotation around a hypothetical axis at the
second ray.
• PRONATION TWIST
• When the hind foot and TTJ are locked in
supination ,the adjustment of forefoot position
will be left entirely to TMT Joints.
• TMT-forefoot medial –lift off the ground
• lateral-press to the ground
1st and 2nd-plantarflex
4th and 5th –dorsiflexion
• Eversion accompanies

73. Arches
• Needed for traction between the floor & foot’s wt bearing
structures.
• Tensed throughout stance phase.
• Compared to a tie rod.
• Plantar plates of mtp resist compressive & tensile forces
transferred through plantar aponeurosis.
• In toe extension- mt heads act as pulleys that pull this fascia–
supination.

75. Gait

76. Phase Strt
position
End
position
Movement GRF Contracti
on
Muscle
Heel strike
– foot flat
Neutral 15 deg PF PF Pronation Eccentric Dorsiflexo
rs
Foot flat-
mid stance
15 deg PF 5-10 deg
DF
DF Posterior
to anterior
Inertia
then
eccentric
PF
Midstance 5-10 deg
DF
Neutral Flexion Anterior concentric PF
Heel off to
Toe off
Neutral 20 deg PF PF Anterior Concentric PF
Accleratio
n
20 deg Pf Neutral DF NO Concentric DF