The ankle/foot complex allows both stability and mobility through its structures. It bears weight and provides stability through the ankle joint and subtalar joint. The ankle joint permits dorsiflexion and plantarflexion around an oblique axis between the talus and tibia/fibula mortise. Ligaments including the deltoid and collateral ligaments support the joints. The talus wedging in the mortise enhances stability in dorsiflexion. Plantarflexion provides less stability.

2.  Ankle/foot complex is structurally analogous to the wrist-
hand complex of the upper extremity.
 Primary role to bear weight.
 The structures of the ankle/foot complex permit both
stability and mobility depending on conditions acting on it.

4.  Stability
• It provide adequate BOS and function as rigid lever for
pushing-off during walking, running, or jumping.

5.  Mobility
• it must also be mobile to adapt to uneven terrain, absorb
shock as the foot hits the ground.

6.  Total 26 foot bones, which functionally divided into 3;
 Forefoot (anterior)
• Metatarsals - 5
• Phalanges - 14
 Midfoot (middle)
• Navicular - 1
• Cuboid - 1
• Cuneiform – 3
 Hindfoot (posterior)
• Talus – 1
• Calcaneus - 1

8.  25 component joints
• Proximal and distal tibiofibular joints – 1-1
• Ankle (talo – crural) joint - 1
• Talo – calcaneal (subtalar) joint - 1
• Talo – navicular joint - 1
• Calcaneo – cuboidal joint - 1
• Tarso – metatarsal joints - 5
• Metatarso – pharangeal joints - 5
• Inter – phalangeal joints - 9

9.  Three cardinal motions :
• Dorsiflexion / Plantarflexion
• Inversion / Eversion
• Abduction / Adduction

10.  Plane : Sagittal plane
 Axis : Coronal axis
 Dorsiflexion decreases the angle between the leg and the
dorsum of the foot, whereas Plantarflexion increases this
angle.
 At the toes, motion around a similar axis is termed
extension (bringing the toes up), whereas the opposite
motion is flexion (bringing the toes down or curling them).

11.  Plane : Frontal plane
 Axis : longitudinal (anteroposterio A-p)axis
 Inversion occurs when the plantar surface of the segment is
brought toward the midline; eversion is the opposite.

12.  Plane : transverse plane
 Axis : vertical axis
 Abduction is when the distal aspect of a segment moves
away from the midline of the body (or away from the
midline of the foot in the case of the toes); adduction is the
opposite.

15.  Pronation / Supination
 Pronation/supination in the foot are motions that occur
around an axis that lies at an angle to each of the axes for
“cardinal” motions.
 Consequently, pronation and supination are terms used to
describe “composite” motions that have components of, or
are coupled to, each of the cardinal motions.
 Pronation = dorsiflexion, eversion, and abduction.
 Supination = plantarflexion, inversion, and adduction.

17.  Valgus refers to an increase in the medial angle between
two bones varus refers to the opposite.
 Valgus (calcaneovalgus) : an increase in the medial angle
between the calcaneus and posterior leg.
 Varus (calcaneovarus) : an decrease in the medial angle
between the calcaneus and posterior leg.

19.  Talocrural joint.
 Articulation
 Proximal : Distal tibia and fibula
 Distal : Body of talus
 Hinge synovial joint with a joint capsule and associated
ligaments.
 It have a single oblique axis with one degree of freedom
around which the motion of dorsiflexion / plantarflexion
occur.

22.  Proximal articular surfaces
• Concave surface of the distal tibia and of the tibial and
fibular malleoli.
• These three facets form an almost continuous concave joint
surface that extends more distally on the fibular (lateral)
side than on the tibial (medial) side and more distally on the
posterior margin of the tibia than on the anterior margin.
• Distal most aspect of fibula known as lateral malleolus.
• Distal tibia and both malleoli resembles and is referred to as
a mortise.

24.  A common example of a mortise is the gripping part of a
wrench. Either the wrench can be fixed (fitting a bolt of
only one size) or it can be adjustable (permitting use of the
wrench on a variety of bolt sizes).
 The adjustable mortise is more complex than a fixed
mortise because it combines mobility and stability
functions.

25.  The mortise of the ankle is adjustable, relying on the proximal
and distal tibiofibular joints to both permit and control the
changes in the mortise.
 The proximal and distal tibiofibular joints are anatomically
distinct from the ankle joint, but functionally likned to the ankle.
 Unlike their upper extremity counterparts, the proximal and
distal radioulnar joints, the tibiofibular joints do not add any
degrees of freedom to the more distal ankle and foot joints.
 However, fusion of the radioulnar joints would have little effect
on wrist range of motion (ROM), whereas fusion of the
tibiofibular joints may impair normal ankle function.

26.  Plane synovial joint.
 Articulation : head of the fibula with the posterolateral aspect
of the tibia.
 A slight convexity of the tibial facet and a slight concavity of
the fibular facet.
 Each proximal tibiofibular joint is surrounded by a joint capsule
that is reinforced by anterior and posterior tibiofibular
ligaments.
 Motion : very small, superior and inferior translation and
rotation of fibula.

29.  syndesmosis, or fibrous union.
 Articulation : concave facet of the tibia and the convex
facet of the fibula.
 The distal tibia and fibula do not actually come into contact
with each other but are separated by fibroadipose tissue.
 Although there is no joint capsule, there are several
associated ligaments at the distal tibiofibular joint.

31.  Function :
• Maintain a stable mortise.
• Support distal tibiofibular joint.
 3 ligaments
• Anterior tibiofibular ligament
• Posterior tibiofibular ligament
• Interosseous membrane
 The interosseous membrane directly supports both proximal
and distal tibiofibular articulations.

32.  Body of talus
 It has three articular surfaces:
• large lateral (fibular) facet
• Smaller medial (tibial) facet
• Trochlear (superior) facet
 The large, convex trochlear surface has a central groove
that runs at a slight angle to the head and neck of the talus.
 The body of the talus also appears wider anteriorly than
posteriorly, which gives it a wedge shape.

33.  The articular cartilage covering the trochlea is continuous
with the cartilage covering the more extensive lateral facet
and the smaller medial facet.

35.  Thin and especially weak anteriorly and posteriorly.
 Therefore, the stability of the ankle depends on an intact
ligamentous structure.

36.  The 3 ligament that supports proximal and distal tibiofibular joint and
mortise.
• Anterior and posterior tibiofibular ligament
• Tibiofibular interosseous ligament
 2 additional ligament that maintain contact between talus and mortise
and control medial-lateral joint stability.
• Medial collateral ligament
• Lateral collateral ligament
 Both of these ligaments also provide key support for the subtalar or
(talocalcaneal) joint that they also cross.

37.  Deltoid ligament
 Fan shaped
 Superficial and deep fibers
 Origin : borders of the tibial malleolus
 Insertion :
• anteriorly on navicular
• Distally on talus
• Posterior on calcaneus

38.  It is extremely strong ligament so injury chances are very
less.
 Eversion and pronation of ankle and talus can injure this
ligament.
 However, these forces may actually fracture and displace
the tibial malleolus before the deltoid ligament tears.

40.  Made up of 3 bands commonly referred to as seperate
ligaments i.e;
• Anterior talofibular ligament
• Posterior talofibular ligament
• Calcaneofibular ligament
 Anterior and posterior talofibular ligament runs horizontal
whereas calcaneofibular ligament runs vertical.

41.  Lateral collateral ligament control inversion and supination
of ankle and talus.
 its weaker and more susceptible to injury than are those of
the medial collateral ligament.

43.  Superior and inferior extensor retinacula
 Superior and inferior peroneal retinacula
 Function : provide stability to ankle and subtalar joint
Along with collateral ligaments.
 the inferior band of the superior peroneal retinaculum,
which lies close and parallel to the calcaneofibular
ligament, appears to reinforce that ligament.

45.  In neutral position of the ankle joint, the joint axis passes
approximately through the fibular malleolus and the body
of the talus and through or just below the tibial malleolus.
 The fibular malleolus and its associated fibular facet on the
talus are located more distally and posteriorly than the
tibial malleolus and its associated tibial facet.
 The more posterior position of the fibular malleolus is due
to the normal torsion or twist that exists in the distal tibia in
relation to the tibia’s proximal plateau.

46. Figure B
Figure A

47.  Figure A. Posterior view showing the mortise around the
body of the talus and the average 14 degree inclination of
the of the ankle axis from the transverse plane.
 Figure B. Superior view showing the ankle axis rotated, on
average, 23 degree from the frontal plane.

48.  Tibial torsion may be defined as the torsion, or twisting,
between the upper and lower ends of the tibiofibular unit.
 This twisting may be reffered as tibial torsion or tibiofibular
torsion (because both the tibia and fibula are involved with
the rotation in the transverse plane) and accounts for the
toe-out position of the foot in normal standing.
 Lateral tibial torsion increases from birth to 10 years of age.

49.  Ankle joint is considerd to have one degree of freedom.
 Dorsiflexion and plantarflexion
 That, occurring between talus and mortise.

50.  Dorsiflexion
 10 to 20 degree
 Motion of the head of the talus dorsally (upward) while the
body of the talus moves posteriorly in the mortise.
 Plantar flexion
 20 to 50 degree
 Opposite Motion of the head and body of talus.

51.  Talar rotation or talar abduction/adduction
 7 degree medial rotation and 10 degree lateral rotation
 Talus may rotate slightly within the mortise in the
transverse plane around a vertical axis.
 Talar tilt 0r talar inversion/eversion
 5 degree or less
 Seen in the frontal plane around an A-P axis.

52. When the foot is weight-bearing, dorsiflexion occurs
by the tibia’s rotating over the talus
As the tibia rotates over the talus, the concave tibiofibular
segment slides forward on the trochlear surface of the talus
Therefore, the wider anterior portion of the talus “wedges”
into the mortise
enhancing stability of the ankle.

53.  The loose packed position of the ankle joint is in plantar
flexion.
 During plantar flexion, only the relatively narrow posterior
body of the talus is in contact with the mortise.
 The ankle is considered to be less stable when in plantar
flexion.
 There is a higher incidence of ankle sprains when the ankle
is plantar flexed than when dorsi flexed.

54.  The asymmetry in size and orientation of the lateral and medial facets
of the ankle joint contribute to changes in the ankle mortise that occur
during ankle movements.
 The lateral (fibular) facet is substantially larger than the medial
(tibial) facet.
 distal fibula moving on the larger lateral facet of the talus must
undergo a greater displacement than the tibial malleolus as the tibia
and fibular move together during dorsiflexion.
 The greater arc of motion for the fibula malleolus than for the tibial
malleolus results in superior/inferior motion and medial/lateral
rotation of the fibula that requires mobility of the fibula at both the
proximal and the distal tibiofibular joints.

56.  Ankle dorsiflexion and plantarflexion movements are
limited primarily by soft tissue restrictions.
 Tension in the triceps surae (gastrocnemius and soleus
muscles) is the primary limitation to dorsiflexion.
 Dorsiflexion is more limited typically with the knee in
extension than with the knee in flexion.

57.  Tension in the tibialis anterior, extensor hallucis longus, and
extensor digitorum longus muscles is the primary limit to
plantarflexion.
 The tibialis posterior, flexor hallucis longus, and flexor
digitorum longus muscles help protect the medial aspect of
the ankle; the peroneus longus and peroneus brevis muscles
protect the lateral aspect.