The document summarizes the biomechanics of the ankle and foot. It describes the anatomy and function of the ankle joint, subtalar joint, transverse tarsal joint, tarsometatarsal joints, metatarsophalangeal joints, and the plantar arches. Key details include the articulating surfaces and ligaments of the ankle joint, the axis of rotation and movements of the subtalar joint, and the factors that maintain the medial and lateral longitudinal arches and transverse arches of the foot.

1. Biomechanics of
ankle and foot

2. Ankle Joint:

3.  ARTICULATING SURFACES:
Proximal Articulating Surface:
composed of concave surface of distal tibia and malleoli of tibial side
and fibular side.
the structure of the distal tibia and two malleoli is referred as mortise.
The structure and function of the proximal and distal tibiofibular joints
permits and control the changes in the mortise.

4. Distal articulating surfaces:
the body of the talus forms the distal articulating surface.
the body of the talus has the three articular surfaces:
i) a large lateral (fibular )facet
ii)a smaller medial (tibial)facet
iii)trochlear(superior) facet

5. Stability of ankle joint
i)Capsule and Ligaments:
the capsule of the ankle joint is fairly thin and weak anteriorly and posteriorly.
Stability of the ankle joint is mostly dependent upon ligaments surrounding
the ankle joint.
main ligaments of the ankle joint:
medial collateral ligament(deltoid ligament)
lateral collateral ligament: i)anterior talofibular ligament
ii)posterior talofibular ligament
iii)calcaneofibular ligament

7. ii)Extensor and peroneal retinaculum:

8.  Axis:
In a neutral ankle position, the joint axis passes approximately through the
fibular malleolus and the body of the talus and through or just below the
tibial malleolus.

9. Function:
Arthrokinematics: i)Dorsiflexion (0-20 degrees)
ii) plantar flexion(0-50 degrees)
During arthrokinematics ,the shape of the body of the talus facilitates joint
stability.
When the foot is weight bearing ,dorsiflexion occurs as the tibia rotates over
the talus.
The loose packed position of the ankle joint is plantar flexion.

10.  Muscles that perform dorsiflexion:
tibialis anterior
the extensor hallucis longus
the extensor digitorum longus
the peroneus tertius

11. Muscles that perform plantar flexion:
Gastrocnemius
soleus
plantaris
Flexor hallucis longus
Flexor digitorum longus
Tibialis posterior
Peroneus longus
Peroneus brevis

12. The Subtalar joint:

13.  The subtalar joint, as its name indicates, resides under the talus .
 Articular Surface:
The large, complex subtalar joint consists of three articulations formed
between the posterior, middle, and anterior facets of the calcaneus and the
talus.

14.  The prominent posterior articulation of the subtalar joint occupies about
70% of the total articular surface area.
 The concave posterior facet of the talus rests on the convex posterior facet
of the calcaneus.
 The articulation is held tightly opposed by its interlocking shape,
ligaments, body weight, and activated muscle

15.  Stability:
The subtalar joint is a stable joint that is rarely dislocated.
The subtalar joint receives support from the ligamentous structures that
support the ankle, as well as from ligamentous structures that only cross the
subtalar joint.
Ligaments include: i)calcaneofibular
ii) lateral talocalcaneal,
iii)cervical,and
iv) interosseous talocalcaneal ligaments.

17.  THE SUBTALAR AXIS:
the axis of rotation is typically described as a line that pierces the lateral-
posterior heel and courses through the subtalar joint in anterior, medial, and
superior directions.

18.  FUNCTION:
Arthrokinematics:
 Pronation and supination of the subtalar joint occur as the calcaneus
moves relative to the talus (or vice versa when the foot is planted)
 Pronation has main components of eversion and abduction.
 Supination has main components of inversion and adduction

19. Transverse tarsal joint
 The transverse tarsal joint, also called the midtarsal or Chopart joint, 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, in essence, immobile
in the weight-bearing foot.

20.  Transverse tarsal joint motion, therefore, is often considered to be motion
of the talus and of the calcaneus on the relatively fixed naviculocuboid
unit.

21. Tarsometatarsal Joint
The tarsometatarsal (TMT) joints are plane synovial joints formed by the
distal row of tarsal bones (posteriorly) and the bases of the metatarsals

22.  Supination twist:
When the hindfoot pronates substantially in weightbearing, the transverse
tarsal joint generally will supinate to some degree to counterrotate the
forefoot and keep the plantar aspect of the foot in contact with the ground.
If the range of transverse tarsal supination is not sufficient to meet the
demands of the pronating hindfoot (or if the transverse tarsal joint is
prevented from effectively serving this function), the medial forefoot will press
into the ground, and the lateral forefoot will tend to lift.

23.  The first and second rays will be pushed into dorsiflexion by the ground
reaction force, and the muscles controlling the fourth and fifth rays will
plantarflex those tarsometatarsal joints in an attempt to maintain contact
with the ground.
 Both dorsiflexion of the first and second rays and plantarflexion of the
fourth and fifth rays 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 tarsometatarsal
joints

25.  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
tarsometatarsal 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.
The muscles controlling the first and second rays will plantarflex those rays in
order to maintain contact with the ground, whereas the fourth and fifth rays
are forced into dorsiflexion by the ground reaction force.

26.  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.

27. Metatarsophalangeal joint
 The five metatarsophalangeal (MTP) joints are condyloid synovial joints
with two degrees of freedom: extension/flexion (or
dorsiflexion/plantarflexion) and abduction/adduction.

28.  Metatarsal break:
The metatarsal break derives its name from the hinge or “break” that occurs
at the metatarsophalangeal joints as the heel rises and the metatarsal heads
and toes remain weightbearing.
The metatarsal break occurs as metatarsophalangeal extension around a
single oblique axis that lies through the second to fifth metatarsal heads.
The inclination of the axis is produced by the diminishing lengths of the
metatarsals from the second through the fifth toes and varies among
individuals.

29.  The angle of the axis around which the metatarsal break occurs may range
from 54° to 73° with respect to the long axis of the foot.

30. Plantar Arches
 There are two types of arches of the foot—
longitudinal and transverse.
LONGITUDINAL ARCH:
Each longitudinal arch has: (a) two pillars, (b) a summit, and (c) joints.
There are two longitudinal arches in each foot: (a) medial and (b) lateral.

32.  Stability of plantar arches:
Factors Maintaining medial longitudinal arch:

33. Factors Maintaining medial longitudinal arch:
Bones :The sustentaculum tali partly support the head of talus.
Ligaments:
(a) plantar calcaneonavicular ligament (spring ligament) which
provides dynamic support to the head of talus,
(b) interosseous ligaments connecting the adjacent bones,
and (c) interosseous talocalcanean ligament, connecting these
bones. These ligaments act as intersegmental ties.

34.  Muscles, tendons, and aponeurosis
1. Acting as slings (i.e., suspending arch from above):
The tendon of tibialis posterior lying underneath the
spring ligament provides dynamic supports to the head of talus and suspends the
arch from above.
The flexor hallucis longus is the bulkiest and strongest
muscle to support the medial longitudinal arch.
2.Acting as tie beams (i.e., structures which prevent separation of the
pillars):
The medial part of the plantar aponeurosis and abductor hallucis
assisted by the flexor hallucis brevis act as tie beam to maintain the height of the
medial longitudinal arch

35.  Factors Maintaining lateral longitudinal arch:

36. Bones :
The proper shaping of the distal end of calcaneus and proximal end of
cuboid.
Ligaments :
1. Short plantar ligament: The short plantar ligament is broad and
thick. It lies deep to the long plantar ligament and supports the calcaneocuboid
joint from below.
2. Long plantar ligament: The long plantar ligament is quite long
and supports the joints between the calcaneum, cuboid, and related
metatarsals.

37.  Muscles, tendons, and aponeurosis :
1. Acting as tie beams: The lateral part of the plantar
aponeurosis and the intrinsic muscles of the little toe (e.g., lateral part of the
flexor digitorum brevis, abductor digiti minimi brevis, and flexor digiti minimi
brevis) function as tie beams of this arch.
2. Acting as slings:The tendons of peroneus brevis and
peroneus tertius and the tendon of peroneus longus.

38. Transverse Arch:
Anterior Transverse Arch:
The heads of the metatarsals form the anterior
transverse arch.
It is a complete arch because during standing position
the heads of first and fifth metatarsals come into contact to the ground and
form the two ends of the arch.

39. Posterior Transverse Arch:
The posterior transverse arch is formed by greater parts of
the tarsus and metatarsus
It is an incomplete arch because only its lateral end comes
into contact with the ground during standing position.
It forms only half of the dome in one foot. The complete
dome is formed when the two feet are brought together

40.  Stability of transverse arch:
Bones :Most of the tarsal and metatarsal bones have larger dorsal and smaller
plantar surfaces (i.e., wedge-shaped), which help to form and maintain the
concavity on the plantar aspect of the foot skeleton.
Ligaments These are small ligaments, which bind together the cuneiform
bones and metatarsals. Superficial and deep transverse metatarsal ligaments
at the heads of metatarsals function as intersegmental ties to maintain the
shallow arch at the heads of metatarsals. Muscles and tendons 1. Acting as tie
beams: The tendons of peroneus longus and tibialis posterior support the
transverse arch as tie beam. 2. Acting as slings: The peroneus tertius and
peroneus brevis on the lateral side and tibialis anterior on the medial side
support the transverse arch as slings. 3. Acting as intersegmental ties: The
dorsal interossei act as intersegmental ties.

41.  Muscles and tendons
1. Acting as tie beams: The tendons of peroneus
longus and tibialis posterior support the transverse arch as tie beam.
2. Acting as slings: The peroneus tertius and
peroneus brevis on the lateral side and tibialis anterior on the medial side
support the transverse arch as slings.
3. Acting as intersegmental ties: The dorsal interossei
act as intersegmental ties.

42.  Function of the arches:
1. Distribute the body weight to the weight-bearing points of the sole (e.g.,
heel; balls of the toes, mainly those of first and fifth toes and lateral border of
the sole).
2. Act as shock absorber during jumping by their springlike action.
3. The medial longitudinal arch provides a propulsive force during
locomotion.
4. The lateral longitudinal arch functions as a static organ of support and
weight transmission.
5. The concavity of the arches protects the nerves and vessels of the sole.

43.  Flat foot (pes planus):
The flat foot is the commonest of all foot problems. It occurs due
to the collapse of medial longitudinal arch.
During long periods of standing the plantar aponeurosis and
spring ligament are overstretched. As a result, the support of the head of talus
is lost and is pushed downward between the calcaneus and the navicular
bones. This leads to flattening of the medial longitudinal arch with lateral
deviation of the foot.

44.  The effects of the flat foot are:
(a) The person usually has clumsy shuffling gait
due to the loss of spring in the foot.
(b) Makes the foot more liable to trauma due to
loss of the shock absorbing function.
(c) The compression of the nerves and vessels
of the sole is due to the loss of concavity of the sole.

45.  High arched foot (pes cavus):
The exaggeration of the longitudinal arch of the foot
causes pes cavus.
This usually occurs because of a contracture (plantar
flexion) at the transverse tarsal joint.
When the patient walks with a high arched foot
there is dorsiflexion of the metatarsophalangeal joints and the plantar flexion
of the interphalangeal joints of the toes.

46.  Hallux valgus:
In this condition, the big toe is deviated laterally at the
metatarsophalangeal joint.
It usually occurs due to constant wearing of pointed shoes
with high heel.
The head of the first metatarsal bone becomes prominent and
rubs on the shoe.
This leads to the formation of protective adventitious bursa called
bunion on the medial side of the big toe.

47.  • Hammer toe:
It is a deformity of the toe in which metatarsophalangeal
and distal interphalangeal joints are hyper-extended but the proximal
interphalangeal joint is acutely flexed.
This deformity usually affects the 2nd and 3rd toes.