Biomechanics of ankle joint

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.

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.

• 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

• 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.

ANKLE JOINTThe 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.

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.

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.

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.

Talocrural joint

Talus

TibiaFibula

<<<Talocrural joint

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

Anterior view

Anterior talo-fibular lig

Anterior tibio-fibular ligtalus

TibiaFibula

Distal articular surfaceTALUS3 Articular Surfaces• Larger lateral facet-triangular shaped• Smaller medial facet-comma shaped• Superior facet- TROCHLEAR

ligaments

• Fibrous capsule• Deltoid or medial ligament- strong

triangular Superficial part Deep part Superficial part-

ANTERIOR TIBIONAVICULAR

MIDDLE TIBIOCALCANEAN

POSTERIOR TIBIOTALAR

Medial view

<Deltoid lig

<Tibialis Ant. Tendon<Tibialis Posterior Tendon

<Navicular

Talus

<Tibia

Deep PartIt 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

Lateral view

Posterior tibio-fibular ><Ant talo fibular

< calcaneofibular

<Peroneal tendonscalcaneus

<Sub talar joint space

Fibula

Posterior view

<Achillies tendon

<Posterior talo-fibular

<Posterior tibio-fibular

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.

Talar rotation(7° med and 10° lat rotation)

Abduction- adduction

Transverse plane

Vertical axis

Talar tilt(5°)

Inversion-eversion

Frontal plane

Anteroposterior axis

Dorsiflexion-plantar flexion

Antero-posterior plane

Frontal axis

•Supination = PF + Adduction + Inversion

• Pronation = DF + Abduction + Eversion

Supination and Pronation

• 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.

Movements

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.

• 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.

Dorsiflexion

peroneus tertius (usually very close to extensor digitorum longus and often considered as part of this muscle)

tibialisanterior

extensordigitorum

longus

extensorhallucislongus(deep to ext.digitorumlongus)

Plantar FlexorsNOTE:1) Soleus liesdeep togastrocnemius

2) Both insert intothe calcanealtendon akaAchilles tendon

Soleus

Gastrocnemius

Posterior View

tibialisanterior

extensorhallucislongus

flexordigitorum

longusflexor

hallucislongus

tibialisposteri

or

Invertorsprimary

NOTE: Muscles passto the medial side ofthe foot!

peroneusbrevis

peroneuslongus

peroneustertius

extensordigitorum

longus

Evertorsprimary

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

• 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

• 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.

• LigamentsCervical ligament- strongestInterosseus talocalcaneal ligament anterior band posterior bandOthers-Calcaneofibular liglateral talocalcaneal ligInferior extensor retinaculum –provides subtalar

supportCervical,interosseus,collaterals-talocalcaneal stability

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.

COMPONENT MOVEMENTSNON- WT

BEARINGWT-BEARING

SUPINATION CALCANEAL

INVERSION(VALGUS)

CALCANEAL

INVERSION(VARUS)

CALCANEAL

ADDUCTION

TALAR ABDUCTION

(LATERAL ROTATION)

CALCANEAL

PLANTAR FLEXION

TALAR

DORSI-FLEXION

TIBIOFIBULAR LAT ROT

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

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).

• CLOSED PACKED POSITION- FULL SUPINATION

• POSITION OF RELATIVE MOBILITY – PRONATION

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.

• 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.

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

• 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)

• Dorsally –dorsal calcaneocuboid ligament, • Inferiorly -plantar calcaneocuboid (short

plantar) and the long plantar ligaments

Midtarsal Joint

Actually consists of two joints: the calcaneocuboid on the lateral side and the talonavicular on the medial side.

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.

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.

The longitudinal axis of the transverse tarsal jointInclined 15° superiorly from the transverse plane

15°

Inclined 9° medially from the sagittal plane.

9°

• 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.

The oblique axis of the transverse tarsaljoint .

Inclined 57° from the sagittal plane 57°

Inclined 52°superiorly from the transverse plane.

52°

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)

• 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.

• 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

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.

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

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).

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.

• LIGAMENTDeep 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.

• 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.

• 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

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

• 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.

• 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

• 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

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.

Windlass mechanism

Gait

Phase Strt position

End position

Movement

GRF Contraction

Muscle

Heel strike – foot flat

Neutral 15 deg PF PF Pronation Eccentric Dorsiflexors

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

Accleration

20 deg Pf Neutral DF NO Concentric DF