Lecture-1
BIO-MECHANICS OF ANKLE-FOOT
JOINT
objectives
An over view of Foot
Ankle joint general consideration
Proximal joint surface of ankle joint
Distal joint surface of ankle joint
Capsular support of ankle joint
Ligamentous support of ankle joint
Osteo kinematics of ankle
Arthro kinematics of ankle joint
Introduction
The ankle/foot complex is structurally analogous to
the wrist-hand complex of the upper extremity but
has a number of distinct differences to optimize its
primary role to bear weight.
The complementing structures of the foot allow the
foot to sustain large weight-bearing stresses under
a variety of surfaces and activities that maximize
stability and mobility.
The ankle/foot complex must meet the stability
demands of:
– (1) providing a stable base of support for the body in
a variety of weight-bearing postures without
excessive muscular activity and energy expenditure
and
– (2) acting as a rigid lever for effective push-off during
gait.
The stability requirements can be contrasted to
the mobility demands of:
– (1) dampening rotations imposed by the more
proximal joints of the lower limbs,
– (2) being flexible enough to absorb the shock of the
superimposed body weight as the foot hits the
ground, and
– (3) permitting the foot to conform to a wide range of
changing and varied terrain.
The ankle/foot complex meets these diverse requirements through the
integrated movements of its 28 bones that form 25 component joints.
These joints include:
–
–
–
–
–
–
–
the proximal and distal tibiofibular joints;
the talocrural, or ankle, joint;
the talocalcaneal, or subtalar, joint;
the talonavicular and the calcaneocuboid joints (transverse tarsal joints);
the five tarsometatarsal joints;
five metatarsophalangeal joints; and
nine interphalangeal joints.
To facilitate description and understanding of the
ankle/foot complex, the bones of the foot are traditionally
divided into three functional segments.
These are:
– the hindfoot (posterior segment), composed of the talus and
calcaneus;
– the midfoot (middle segment), composed of the navicular,
cuboid, and three cuneiform bones; and
– the forefoot (anterior segment), composed of the metatarsals
and the phalanges
These terms are commonly used in descriptions
of ankle or foot dysfunction or deformity and are
similarly useful in understanding normal ankle
and foot function.
Kinematics of Foot
Gross motion occurs in three planes
– Flexion/extension – sagittal plane
– Abduction/adduction – transverse plane
– Inversion/eversion – frontal plane
Supination –inversion/flexion/adduction
Pronation- eversion/extension/abduction
WB range differs from NWB
ER/IR of leg affects arch of foot
valgus (or calcaneo
valgus )
– increase in medial angle
b/w calcaneus and
posterior leg.
varus (or calcaneovarus)
– decrease in medial angle
b/w calcaneus and
posterior leg
Proximal Articular Surfaces
The proximal segment of the ankle is composed of the
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.
The structure of the distal tibia and the malleoli resembles and
is referred to as a mortise.
Distal Tibiofibular Joint
The distal tibiofibular joint is a syndesmosis, or fibrous union, between
the 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.
Because the proximal and distal joints are linked (the tibia, fibular, and
tibiofibular joints are part of a closed chain), all the ligaments that lie
between the tibia and fibular contribute to stability at both joints.
Distal Articular Surface
The body of the talus forms the distal articulation of the
ankle joint. The body of the talus has three articular
surfaces: a large lateral (fibular) facet, a smaller medial
(tibial) facet, and a 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.
The degree of wedging may vary among individuals, with
no wedging at all in some and a 25% decrease in width
anteriorly to posteriorly in others.
The articular cartilage covering the trochlea is continuous
with the cartilage covering the more extensive lateral
facet and the smaller medial facet.
The structural integrity of the ankle joint is maintained
throughout the ROM of the joint by a number of important
ligaments.
Prox TF jt
–
–
–
–
Flat facet
Incline
Sup / inf sliding
Fibular rotation
Ant post Tibiofibular
lig (At proximal n distal
both)
TF
Syndesmosis
Ant /post TF lig
Interosius membrane
Crural tibio fibular inter lig
Fibula non wt bearing
ANKLE JOINT:
Synovial hinge jt
Oblique axis
One degree freedom
DF/PF (movt)
Ligamentous support of ankle joint
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).
Deltoid ligament
Tibialis Posterior Tendon
Navicular ---
medial collateral ligament (MCL)
The MCL is most commonly called the deltoid
ligament cx fan shaped
Origion and insertion:
Arise 4m tibial malleolus and insert in a
continuous line on the navicular bone anteriorly
and on the talus and calcaneus distally and
posteriorly.
Mcl control and limits….
control medial distraction stresses on the ankle
joint
limits motion at the extremes of joint range,
particularly with calcaneal eversion.
Valgus force fracture displace tibial melloli before
ligament tears.
lateral collateral ligament (LCL).
The LCL is composed of three separate bands that
are commonly referred to as separate ligaments.
These are the anterior and posterior talofibular
ligaments and the calcaneofibular ligament,
LCL control and limits:
The LCL helps control varus stresses that result in
lateral distraction of the joint
check extremes of joint ROM, particularly calcaneal
inversion.
Ligaments
Ant Talo Fibular weakest and most commonly torn
ligament is most easily stressed when ankle is in a
plantarflexed and inverted position
Rupture of the anterior talofibular ligament often
results in anterolateral rotatory instability
posterior talofibular ligament is the strongest of
collateral ligaments and is rarely torn in isolation.
dorsiflexion of head of talus dorsally (or upward)
Body of talus moves posteriorly in mortise.
Plantar flexion is the opposite motion
talus may rotate slightly within the mortise in both transverse plane around a
vertical axis (talar rotation or talar abduction/adduction) and in the frontal
plane around an A-P axis (talar tilt or talar inversion/eversion)
7 of medial rotation and 10 of lateral rotation in the transverse plane.
Talar tilt (A-P axis) averages 5 or less
Ext rotation of 9 degrees from neutral to 30
degrees of dorsiflexion
0-10 degrees of plantar flexion, talus internally
rotate 1.4 degrees
At 30 degree of plantar flexion, talus ext rotate
to 0.6 degrees.
Osteokinematics of ankle joint
range of motion (ROM)
0-20º for ankle dorsiflexion
0-55º for ankle plantar flexion
Joints of mid foot contribute 10-41% of plantarflexion from
neutral to 30 degrees of plantarflexion.
Gait:
Heel strike: slight plantar flexion
Increases till flat foot
Mid stance dorsiflexion starts.
Toe off : plantar flexion
Middle of swing phase: dorsiflexion
Slight plantar flexion at heel strike.
Max dorsiflexion at 70 % of stance
Max plantar flexion at toe off.
arthrokinematic movements (convex on
concave)
posterior glide of the talus on the ankle mortise
with ankle dorsiflexion
anterior glide of the talus on the ankle mortice
with ankle plantarflexion
Regarding peripheral jt mob
resting position： slight ankle plantarflexion
(10º)
closed packed position： full ankle dorsiflexion
Foot Positions
Subtalar or talocalcaneal joint
– Inversion & eversion
Pronation = ankle dorsiflexion + subtalar
(calcaneal) eversion + forefoot abduction
(external rotation)
Supination = ankle plantarflexion + subtalar
(calcaneal) inversion + forefoot adduction
(internal rotation)
Foot Positions
Transverse tarsal joints
Talonavicular joint
Calcaneocuboid joint
– compound joint known
as the transverse
tarsal joint line
– that transects the foot
head of talus “ball”
anteriorly concavity of navicular “socket”
inferiorly concavities of anterior and medial calcaneal
facets and by the plantar calcaneonavicular ligament;
medially by deltoid ligament
laterally by the bifurcate ligament
(“socket”) by navicular bone anteriorly,
deltoid ligament medially
medial band of bifurcate lig laterally
spring (plantar calcaneonavicular) lig inferiorly
Role of spring ligament
support for the medial longitudinal arch little or no elasticity.
Keystone
Arches of the Foot
Medial Longitudinal Arch
Lateral Longitudinal Arch
Transverse Arch
Medial Longitudinal Arch
–
–
–
–
–
–
Calcaneus
Talus
Navicular
1-3 cuneiforms
1-3 MT’s
Function
Arches of the Foot
Medial Longitudinal
Arch continued
– Ligament Support
• Plantar
Calcaneonavicular
(spring)
• Long Plantar Lig
• Deltoid
• Plantar fascia
Arches of the Foot
Medial Longitudinal Arch
continued
– Muscular Support
• Intrinsic
– Abductor Hallucis
– Flexor Digitorum
Brevis
• Extrinsic
– Tibialis Posterior
– Flexor Hallucis Longus
– Flexor Digitorum
Longus
– Tibialis Anterior
Arches of the Foot
Lateral Longitudinal Arch
– Composed of
• Calcaneus
• Cuboid
• 4-5th MT’s
– Ligament Support
• Long & Short Plantar
• Plantar Fascia
Arches of the Foot
Lateral Longitudinal Arch
continued
– Muscle Support
• Intrinsic
– Abductor Digiti Minimi
– Flexor Digitorum Brevis
• Extrinisic
– Peroneus Longus,
Brevis & Tertius
Arches of the Foot
Transverse Arch
– Formed By:
– Ligament Support
• Intermetatarsal Ligaments
• Plantar Fascia
– Muscle Support
function
Shock absorber
Weight bearing
Prevent blood vessels and other soft
tissue from being crushed
• All intrinsic muscles
• Extrinisic
– Tibialis Posterior
– Tibialis Anterior
– Peroneus Longus
Medial longitudinal arch
It is
higher
more mobile
more resilient
Than the lateral arch
Absorbs forces of thrust & weight
Medial Longitudinal Arch in Gait
In normal gait medial
longitudinal arch raised
during heel strike ,
providing a rigid foot for
weight transmission
And during foot flat
medial longitudinal arch
is depressed providing a
flexible support to adapt
to uneven
ground/surfaces
Pathomechanics of Medial Longitudinal Arch
Pes Cavus
Pes cavus is a high arch that does
not flatten with weightbearing.
deformity can be located in forefoot,
midfoot, or hindfoot or in a
combination of these sites.
Pathomechanical Causes
clawing of toes
posterior hindfoot deformity
(described as an decreased
calcaneal angle),
Contracture/tightening of the
plantar fascia
cock-up deformity of the great
toe.
This can cause increased
weightbearing for the metatarsal
heads and associated
metatarsalgia and callus
formation.
Pathomechanics due to Pes Cavus
Foot is inverted Calcaneus is inverted/varus
Big toe usually plantar flexed and other toes dorsiflexed at
metatarsophalangeal joint resulting in claw foot deformity
During gait the arch is not depressed even in foot flat phase
resulting in loss of adaptation to uneven surfaces
lateral foot pain from increased weightbearing on the lateral
foot.
Metatarsalgia
Ankle instability can be a presenting symptom, especially in
patients with hindfoot varus and weak peroneus brevis muscle.
Patients with neuromuscular disease complain of weakness
and fatigue
Pes Planus
Flatfoot may be classified as congenital or acquired.
Congenital flatfoot can be further divided into rigid and flexible.
Congenital rigid flatfoot is due to a structural bony abnormality
such as vertical talus
Congenital flexible flatfoot is mostly physiological,
asymptomatic and requires no treatment
Pathomechanical Causes
Posterior tibial tendon dysfunction (PTTD). This tendon is vital to the
maintenance of the medial arch. Attenuation or rupture of the PTTD
tendon will cause a flatfoot deformity
Tarsal coalition. This is a congenital condition where bones in the
midfoot and hindfoot are abnormally joined together. This causes a
reduced range of movement and the transfer of mechanical forces to
other joints causing pain.
Peroneal spastic flatfoot is a name given to flatfoot deformity with
increased tone in the peroneal muscles. These muscles evert the foot
and disrupt the balance of muscular pull around the ankle
Pathomechanics due to Pes Planus
Charcot foot. This is flatfoot, sometimes a rocker bottom foot, associated with a
peripheral neuropathy. (Lax Plantar Fascia)
The heel bone, when viewed from rear is everted or in valgus.
Flatfeet may cause, other biomechanical causes of pain for example, genu valgum
(knock knees), medial or anterior knee pain, Achilles tendonitis, and low back pain
During Heel Srtrike in the gait cycle the longitudinal arch is not present , thus not
able to provide a rigid foot for weight transmission
Foot is everted, Forte foot is Abducted and
pronated
This causes the Big toe to abduct and go
into a valgus position resulting in Hallux
Valgus Deformity
weight transmission is displaced from head
of 1st metatarsal to head of 2nd and 3rd
metatarsal resulting in an abnormal weight
bearing
Metatarsal head’s lateral surface in Big toe
valgus deformity rubs against the shoe
and results in callus formation
Arches of the Foot
Arches of the Foot
Arch Positions
Normal
High arch: Pes cavus
Low arch (flat foot):
Pes planus
Ankle Joint Stability
Distal ends of tibia and fibula – like mortise
(pinchers) of adjustable wrench
Tibia is weight bearing
Fibula is considered non-weight bearing – may
hold up-to 10% of body weight
Multiple ligaments
Ligaments and Sprains
Ligaments and Sprains
Movements & Major Muscles
Dorsiflexion: Tibialis anterior
Plantar flexion: Gastrocnemius & soleus
Inversion: Tibialis anterior, peroneus longus &
peroneus brevis
Eversion: Peroneus tertius
Biomechanics of Gate
Stance phase (60-65%)
–
–
–
–
–
Heel contact (heel strike or initial contact)
Foot flat (loading response)
Mid stance
Heel off (terminal stance)
Toe off
Swing phase (35-40%)
– Toe off (acceleration or initial swing)
– Mid swing
– Heel contact (deceleration or terminal swing)
THANK YOU