Ankle is a complex not a simple joint. this slide show demonstrates detailed description about ankle anatomy and biomechanics

1. Ankle Complex: Anatomy,
Biomechanics
Radhika Chintamani

2. Contents
• Introduction
• Ankle joint
• Talocalcaneal joint
• Tarsal joints
• Metatarsal joints
• Metatasophalangeal joints
All the above mentioned joints are described on the basis of
Introduction, Anatomy, Biomechanics
• Tarsal Tunnel
• Foot arches
• Windlass mechanism

3. Introduction
• Ankle - foot complex is
comprises of distal tibia and
fibula, the seven tarsal bones,
five metatarsals and fourteen
phalanges. It analogues to that
of wrist & hand complex.
• The interdependence of the
ankle & foot with the more
proximal joints of the lower
extremities & great weight
bearing stresses to which these
joints are subjected have
resulted in a greater frequency &
diversity of problems in ankle –
foot complex.

4. Introduction
• The distal tibia comprises of three
malleolii, namely;
a. Medial malleolus: it is the distal
part of tibia projecting medially in
the ankle.
b. Lateral Mallelous: it is the distal
part of fibula projecting laterally in
the ankle.
• Third mallelous: The posterior
margin of the distal tibia is
sometimes referred to as the third
malleolus because it projects
distally beyond the superior
surface of the talus and contributes
to the stability of the ankle joint

5. Alignment of tibia
• The distal portion of the tibia is laterally
rotated in the transverse plane with
respect to the proximal end of the tibia,
creating a normal lateral, or external,
tibial torsion. Lateral torsion of the
tibia moves the medial malleolus
anteriorly and consequently influences
the position of the foot with respect to
the leg, affecting posture and gait.
Tibial torsion is measured in a variety of ways, including by the angle between a line
through the tibial plateaus and a line through the medial and lateral malleoli.

6. Ankle complex
• The ankle complex exhibits three-dimensional motion and six
degrees of freedom, with rotations about and translations
along medio-lateral, anterior-posterior, and longitudinal axes.

7. Torsional Deformities of the Tibia
• Medial torsion of the tibia is the second most common cause of an intoeing
posture, following only excessive femoral anteversion. Excessive lateral or
external tibial torsion deformities are associated with increased Q angles
and recurrent patellar dislocations. Skeletal malalignments in the lower
extremity can contribute to abnormal loading patterns anywhere in the
lower extremity, and clinicians should consider tibial torsion when assessing
skeletal alignment of the lower extremity.

8. Functionally Ankle Complex is divided into 3
complexes
• Fore foot/anterior segment
(metatarsals & phalanges)
• Midfoot/middle segment
(cuboid, navicular & 3
cuneiforms)
• Hindfoot/posterior
segment (talus &
calcaneus)

9. Ankle Joint
• Type of joint: it is a synovial type of
joint a hinge variety.
• Articulating surfaces:
a. Proximal: concave surface of distal
tibia and fibular malleoli forming a
mortise. The articular surface of the
distal tibia, known as the plafond,
b. Distal: convex surface of talus: a large
lateral part for fibular facet, a small
medial facet and a trochlear facet.

10. • Degree of motion: It has one degree
of motion
• Axis of motion: Joint axis passes
approximately through the fibular
maleolus, the body of the talus and
through or just below the tibial
maleolus.

11. • Capsules of ankle joint: thin
compared to other joints, and
weak anteriorly and posteriorly.
• Ligaments of ankle joint: The two
major ligaments associated with
the ankle joint are medial
collateral ligament (Deltoid
ligament: controls valgus stress
and checks calcaneal eversion)
and the lateral collateral
ligament (controls varus stress
and checks calcaneal inversion).

12. KINEMATICS
• Sagittal plane and coronal axis
a. Osteokinematics: one degree of freedom occurs in sagittal plane and coronal axis
i. Dorsiflexion: 10-20deg
ii. Plantarflexion: 20-50deg
b. Arthrokinematics:
i. Dorsiflexion: in open kinematics chain the talus roll anteriorly while glide
posteriorly in relatively fixed mortise. While in weight bearing or in closed
kinematic chain the tibia rotate over the talus (roll and glide in anterior direction).
The anterior portion of talus is wider than posterior so it leads to the firm contact
of anterior wider surface of talus with the mortise leading to closed pack position
of joint.
ii. Plantarflexion: , in open kinematic chain the talus roll posteriorly and glide
anteriorly in mortise. While in weight bearing the tibia will roll and glide
posteriorly on talus. As the posterior surface of talus is less wider than anterior
surface so it will lead to loose pack position of the joint

13. Note
• The talus may rotate slightly within the mortise in both the transverse
plane around vertical axis (talar abduction/ adduction) and frontal plane
around A-P axis (talar inversion/eversion). These motions are quite small,
with maximum 7⁰ of medial rotation and 10⁰ of lateral rotation and
average 5⁰ or less of the talar inversion and eversion.
• Open chain : Follows convex-concave rule.
• Closed chain: Follows concave-convex rule.

14. KINETICS
i. Dorsiflexion: Primary Dorsiflexorsof the ankle is Tibialis anterior and
secondary are (moment arm is small to cause movement at ankle but large
to cause movement in further foot complex): Extensor hallucis longus,
brevis and extensor digitorum.
ii. Plantarflexion: Primary plantar flexors of the ankle are two heads of
gastrocnemius and soleus. Secondary plantarflexors (moment arm
of plantarflexion is small) are: planatris, tibialis posterior, the flexor
hallucis longus, the flexor digitorum longus, the peroneus longus
and the peroneus brevis muscle.

15. Note
• Active or passive tension in the Triceps surae is the primary limitation to
Dorsiflexion. Dorsiflexion is more limited typically with the knee in
extension than with knee in flexion because gastrocnemius muscle is
lengthened over two joint when knee is extended.
• Tension in Tibialis anterior, Extensor hallucis longus and Extensor digitorum
longus muscles is the primary limit to plantar flexion.

16. Functions of Ankle joint
 Support for the entire body
 Propulsion through space
 Adaptation to uneven terrain
 Absorption of shock
Ankle foot complex meets its diverse requirements through its 28
bones that form 25 component joints

17. SUBTALAR JOINT
• Type of joint: it is a composite joint
• Degree of motion: triplanar movement
around a single joint axis
• Articulating surfaces:
a. Superiorly: Talus
b. Inferiorly: Calcaneal
• Posterior articulation: concave facet on
the undersurface of the body of the
talus & a convex facet on the body of
the calcaneus.
• The anterior & the middle talocalcaneal
articulations are formed by 2 convex
facets on the inferior body & the neck
of the talus & 2 concave facets on the
calcaneus.

18. Axis of motion
a) Inclined 42deg upward and anteriorly
from the transverse plane.
b) Inclined medially 23deg from sagittal
plane.
• Note: Hence, motion around this
oblique axis will cross all three planes.
• Because of this obliquity of the axis of
STJ, the motion at this joint cannot
and do not occur independently but
follow a characteristic pattern which
has following component .
• Pronation (25-30º ) : is an oblique
plane movt composed of three
cardinal plane components .
Eversion- Dorsiflex-Abduction.
• Supination (50º ) : is an oblique plane
movt composed of three cardinal
plane components.
Inversion- Plantarflex- Adduction.

19. • Osteokinetics: it is divided into two
types; weight bearing and non-weight
bearing joint motions:
a. Non-weight bearing joint motions:
b. Weight bearing joint motions:
Supination Pronation
Calcaneal inversion Calcaneal eversion
Calcaneal adduction Calcaneal abduction
Calcaneal Plantarflexion Calcaneal Dorsiflexion
Supination Pronation
Calcaneal inversion Calcaneal eversion
Talar adduction Talar abduction
Talar Plantarflexion Talar Dorsiflexion
Tibiofibular lateral
rotation
Tibiofibular Medial
rotation

20. KINEMATICS
• Frontal plane for inversion and eversion and Transverse plane for
abduction and adduction
a. Osteokinematics: triplanar movement around single axis
i. Weight Bearing: described in the previous slide
ii. Non-weight bearing: described in the previous slide
b. Arthrokinematics: The alternating convex and concave facets limit
mobility and create a twisting motion of the calcaneus on the talus.
• Inversion: the calcaneus slides laterally on a fixed talus.
• Eversion: the calcaneus slides medially on the talus.

21. NOTE
In weight bearing the calcaneus is aligned so that only its posterior
aspect contacts the ground and directly sustains ground reaction forces.

22. Other joints of foot complex
• Calcaneocuboidal joint.
• Talo-navicaular joint.
• Tarsometatarsal joints
• Metatarsophalangeal joints.
• Interphalangeal joints.

23. Other joints of foot complex

24. Supporting Structures
i. Lateral collateral ligament
ii. Anterior talofibular
iii. Posterior talofibular
iv. Calcaneofibular
i. Deltoid Ligament
ii. Tibionavicular
iii. Spring ligament
iv. Tibiospring ligament
v. Posterior tibiotalar

25. SATBILITY OF THE ANKLE JOINT
• Stability of the ankle joint often is described in terms of the anterior,
posterior, medial, and lateral translation, or shift, of the talus within
the mortise and by the amount of medial or lateral talar tilt about an
anterior–posterior axis, which occurs when force is applied.
•The deltoid ligament is positioned to
limit lateral tilt and lateral shift of the
talus.
•The lateral malleolus and lateral
supporting structures also appear to
provide important limits to lateral talar
shift by acting as a buttress against the
movement. The lateral collateral
ligament, especially the anterior
talofibular and calcaneofibular
ligaments, prevent excessive medial
tilt of the talus.

26. SATBILITY OF THE ANKLE JOINT
• Anterior glide of the talus is limited by the lateral malleolus and
lateral collateral ligaments and by the deltoid ligament, although the
lateral supporting structures appear to be primary.
• Posterior glide of the lateral malleolus is limited primarily by the
posterior talofibular and calcaneofibular ligaments.
• Plantar- and dorsiflexion alter the tension within the individual
components of the collateral ligaments.
• Anterior glide of the talus is greatest with the ankle close to neutral
and is more restricted when the ankle is either dorsiflexed or
plantarflexed.

27. CLOSED-CHAIN Motion of FOOT
• The distal end is fixed during motion, i.e. when foot complex is weight
bearing.
• When the foot is fixed to the ground, the foot pronates and supinates by
allowing the proximal segments to move on the distal segments.
• Thus pronation of the subtalar joint occurs by the tibia and talus moving
on the calcaneus. Pronation with the foot fixed on the ground produces
medial rotation of the tibia, which carries the talus medially within the
mortise. As the talus moves medially, the calcaneus everts and pulls the
cuboid and navicular into abduction and eversion.
Thus, Pronation of foot comprise of: Eversion, Dorsiflexion and ABduction.
(PEN-DAB)

28. CLOSED-CHAIN Motion of FOOT
• Thus supination of the subtalar joint occurs by the tibia and talus
moving on the calcaneus. Supination with the foot fixed on the
ground produces lateral rotation of the tibia, which carries the talus
laerally within the mortise. As the talus moves laterally, the
calcaneus inverts and pulls the cuboid and navicular into adduction
and inversion.
Thus, Supination of foot comprise of: Inversion, Plantarflexion and
ADduction. (SIN-PAD)

29. Arches of the Foot
A. Longitudinal arch- Medial .
Lateral .
B. Transverse arch- Anterior .
Posterior.
Functions of arches
1.Distributes the wt of the body to the wt bearing areas of the sole.
2.Acts as spring, which are of great help in walking and running
3.Act as shock absorbers in stepping and jumping .
4.Concavity of the arch protects the soft tissue of the sole against the
pressures

30. Transverse arches
Longitudinal arches
Medial Longitudinal Arch Lateral Longitudinal Arch
Arches of the Foot

31. 1.Bony factor
The posterior transverse arch is formed and maintained by tarsal bone
(cuneiform) and the heads of the metatarsal bone which wedge shaped ,the
apex pointing downwards.
2. Intersegmental ties
• Supported by ligaments , and intrinsic muscles of which the important ones
are:
-Spring ligament : medial longitudinal arch.
-The long & short plantar ligament: lateral longitudinal arch
-Interosseus muscles: transverse arch.
Structures responsible for maintenance of Arches

32. 3. Tie beams (connect the two ends of the arch):
Longitudinal arches: plantar aponeurosis prevents the flattening of the arch
Transverse arch : adductor hallucis act as tie beam.
4. Slings (keep the summit of the arch pulled up):
- Medial longitudinal arch: pulled by tendon passing from the posterior
compartment of the leg into sole (tibialis post, FHL, FDL).
- Lateral longitudinal arch: pulled upward by peroneus longus and brevis.
- Tendons of tibialis ant and peroneus longus together form a sling which keeps
middle of the foot pulled upwards, supporting the longitudinal arches.
- Peroneus longus runs transversely across the sole it pull the medial and lateral
margin of the sole closer together , maintaining the transverse arch .
Structures responsible for maintenance of Arches

33. MUSCLES OF FOOT
The muscles of the foot can be divided into plantarflexors, dorsiflexors,
evertors and inverters, adductors and abductors.
There are no specific muscle for supination and pronation as the movements are
not pure and occur along with other movements as already discussed.
Muscle name Origin Insertion Nerve supply Action
Tibialis anterior Upper two thirds
of lateral surface
of tibia
Medial cuneiform
and first
metatarsal bone
Dorsiflexion and
inversion
Extensor hallucis
longus
Middle portion of
the fibula on the
anterior surface
and interosseous
membrane
Inserts on the
dorsal side of the
base of the disatl
phalanx of great
toe
Deep fibular
nerve
Deep fibular
nerve
Extension of
great toe, assist
in dorsiflexion
Extensor hallucis
brevis
Calcaneus Proximal phalanx
of great toe
Extension of
great toe

34. Muscle name Origin Insertion Nerve supply Action
Gastrocnemius 2 heads-
Medial: from posterior
surface of medial
femoral condyle
Lateral: from posterior
surface of lateral
femoral condyle
Froms a tendon named
Tendo-Achilles with
Soleus and gets inserted
into Middle facet on
posterior surface of
calcaneum
Tibial nerve Strong plantarflexor
Soleus Posterior aspect: of
fibular head and
medial border of tibial
shaft
Tibialis
posterior
Inner borders of fibula
and tibia on posterior
surface
Navicular bone and
medial cuneiform bone
Tibial nerve Assists in plantar
flexion and inversion
Plantaris Inferior part of the
lateral supracondylar
ridge of femur
Into Achilles tendon Tibial nerve Plantar flexion
Peroneus
longus
Proximal part of
lateral surface of shaft
of fibula
First metatarsal, medial
cuneiform
Superficial fibular nerve Eversion and
plantarflexion
Peroneus brevis Distal part of lateral
surface of shaft of
fibula
Fifth metatarsal

35. • The ground reaction force produces an external extension, or dorsiflexion,
moment of 47.4 Nm that requires an internal, plantarflexion moment of
equal magnitude produced by the plantarflexor muscles.
• The plantarflexor muscles provide the necessary force to lift the body
weight from the floor, and the calcaneus provides a large moment arm for
the plantarflexors, enhancing their mechanical advantage.
• Important role that the calcaneus plays during upright stance.
• Despite the advantage of the plantarflexors and the reduced moment arm
of the ground reaction force, the joint reaction force on the ankle during
tiptoe stance is almost twice body weight.
FORCE ANALYSIS

36. It is a narrow space lying on the medial side of the ankle joint. The tunnel is
covered with a thick flexor retinaculum that protects and maintains the
structures underneath.
Tarsal tunnel is formed of tarsal bones namely;
1. Calcaneus
2. Talus
3. Cuboid
4. Navicular
5. Medial, middle and lateral cunieforms
TARSAL TUNNEL

37. • It refers to the function of the plantar aponeurosis supporting the foot during
weight bearing activities.
• It directs a direct stretch on the plantar aponeurosis which can be effective in
examining dysfunction of the plantar fascia.
• Vertical forces from body weight travel downward via tibia and tend to flatten
the medial longitudinal arch.
• Ground reaction force travel upward on the calcaneus and the metatarsal
heads, which further attenuates the flattening of the arch as both forces fall
posterior and anterior to tibia.
WINDLASS MECHANISM

38. • Plantar fascia due to its orientation and strength prevents collapse of the arch.
• This is known as windlass mechanism.
WINDLASS MECHANISM

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