Bio Mechanics of Ankle and Foot

Biomechanics of

Ankle and Foot

Ankle Joint

Tibia and Fibula

Talus

Bone Anatomy• Ankle Mortise

– Leg•Tibia

– Weak point - distal 1/3

•Fibula – Attached to

tibia via interosseus membrane

– Talus

Tibia-Fibula Fixation• Interosseous

Membrane• Distal

Tibiofibular Ligament– Anterior – Posterior

Function of Lower Leg

• Lower leg provides– Support for the entire body– Propulsion through space– Adaptation to uneven terrain– Absorption of shock

Ankle Ligaments

• Lateral • Medial

1

Lateral Ankle Liagaments

• 3 primary Lateral ankle ligaments– Anterior talofibular– Posterior talofibular– Calcaneofibular

• Support and maintenance of bone apposition

• Prevent inversion of the foot associated with plantar flexion

Lateral ankle Liagaments

Medial Ankle Liagaments

• Triangular in shape with two smaller ligaments beneath

• Usually called “Deltoid Ligament”• Runs from the medial malleolus of the

tibia to the talus, and the navicular bone– Anterior Tibiotalar part– Posterior Tibiotalar part– Tibiocalcaneal part– Tibionavicular part

Medial Ankle Liagaments

• Provide a great deal of stability to the medial side of the ankle

• Prevent eversion of the foot associated with dorsiflexion

• Rarely injured in sports

Medial Ankle Ligament

Joints of Ankle

• Tibiofibular joint – Amphiarthrodial joint– Space in-between is called the

mortise

• Talocrural joint or Ankle joint– Modifies hinge joint formed by the

tibia, lateral malleolus of the fibula, and the talus

Movements

• Dorsiflexion

– “Raising the

toes”

• Plantarflexion

– “Point the toes”

Ankle Goniometry

• Dorsiflexion– 0-25 degrees

• Plantarflexion– 0-50 degrees

• Normal gait requires 10 degrees of dorsiflexion and 20 degrees of plantar flexion with the knee fully extended

• Joint reaction force in stance is 4 times BW

Muscles

• Anterior compartment• Posterior compartment

– Deep group– superficial group

• Lateral compartment

Anterior compartment

• Tibialis anterior• Extensor digitorum• Extensor hallucis longus

Extensor Extensor DigitoruDigitoru

m m LongusLongus

Extensor Extensor Hallicus Hallicus LongusLongus

Tibialis Tibialis AnteriorAnterior

Posterior compartment

• Superficial group– Gastrocnemius– Soleus– Plantaris

GastrocGastroc SoleusSoleus PlantarisPlantaris

Posterior compartment

• Deep group– Tibialis posterior– Flexor digitorum longus– Flexor hallucis longus

Flexor Flexor Digitorum Digitorum

LongusLongus

Flexor Flexor Hallicus Hallicus LongusLongus

Tibialis Tibialis PosteriorPosterior

Lateral compartment

• Peroneus longus• Peroneus brevis• Peroneous tertius

Peroneus Peroneus LongusLongus

Peroneus BrevisPeroneus BrevisPeroneuPeroneus Tertiuss Tertius

Foot

Foot• Serves as

– A base of support provides a stable platform

– A shock absorber– A mobile adapter generates propulsion– A rigid lever at push-off

• Divided into 3 parts– Hind foot– Midfoot– Forefoot

Hindfoot

• Talus

Hindfoot

• Calcaneous

Midfoot

• Navicular– Bridges movements between the

hindfoot and forefoot

• Cuboid• 1st, 2nd, 3rd Cuneiforms

Forefoot

• 5 metatarsals• 14 phalanges• Work together to form arches

which distribute body weight throughout the foot

Phalanges (14)

Metatarsals (5)

Joint of Hindfoot

• Subtalar joint– articulation between talus and

calcaneus– classified as gliding joint– Converts tibial rotation to forefoot

supination and pronation

Subtalar Axis

Subtalar Axis

• Triplanar/oblique• (Up, forward and medial)• Inclined up approximately 420

• Inclined medially approximately 160

Movements of Subtalar Joint

• Supination– Adduction – Inversion– Plantarflexion

• Pronation – Abduction – Eversion – Dorsiflexion

Ideal Rearfoot Alignment

Forefoot Valgus

Foot Supination

Calcaneus invertsTalus adducts and dorsiflexes

Forefoot Varus

Foot Pronation

Calcaneus everts Talus adducts and flexes

Locking and Unlocking Joint

Joint of Midfoot

• Transverse tarsal joint– articulation

between talus, navicular, calcaneus and cuboid bones

– classified as gliding joint

• Movements– Forefoot abduction

and adduction

Action of the Transverse Tarsal Joint

• Transitional link between the hindfoot and the forefoot

• Hindfoot supination provides rigid lever

• When hindfoot is supinated, Transverse tarsal joint’s ability to compensate is restricted

Action of the Transverse Tarsal Joint

• When hindfoot is pronated, Transverse tarsal joint can compensate to maximize forefoot contact

Action of the Transverse Tarsal Joint

Tarsometatarsal joints

• Medial cuneiform with 1st metarsal bone

• Intermediate cuneiform with 2nd metarsal bone

• Lateral cuneiform with 3rd metarsal bone

• Cuboid with 4th and 5th metarsal bone• Small gliding joints• Allow foot to adapt to uneven surfaces

during gait

Metatarsophalangeal joints

• All are condyloid joints• Flexion/extension (dorsiflexion

and plantarflexion), Abduction/Adduction

• More dorsiflexion than plantar to allow body to pass over MP joints when walking

Interphalangeal joints

• Hinge joint• Phalanges

work to transition weight from one foot to the other

Arches of Foot

• Longitudinal Arch– Lateral Longitudinal Arch– Medial Longitudinal Arch

Arches of Foot

• Transverse Arch

Functions of Arches

• Support• Shock absorption

– Medial Longitudinal Arch• Weight transmission

– Lateral Longitudinal Arch• Increase mobility

Ligamentous Support

• Primary supporting ligaments of archs of foot are– Calcaneonavicular ligament (spring)– Long plantar ligament– Plantar fascia (plantar aponeurosis)– Short plantar ligament (plantar

calcaneocuboid)

Plantar Fascia

Function of Arches

• Support body weight• Lever in • Pedal arch is dynamic• Ligaments active in standing• Muscle active in propulsion

Windlass Mechanism

Windlass Mechanism

Classifying Arch Type

• Normal• Pes Planus: Flat foot• Pes Cavus: High Arch

Blood and Nerve Supply of Foot

Muscles of the foot

• Intrinsic- muscle has both attachments within the foot

• Extrinsis- muscle has one attachment outside of the foot

Extensor Extensor DigitoruDigitoru

m m LongusLongus

Extensor Extensor Hallicus Hallicus LongusLongus

Tibialis Tibialis AnteriorAnterior

GastrocGastroc SoleusSoleus PlantarisPlantaris

Flexor Flexor Digitorum Digitorum

LongusLongus

Flexor Flexor Hallicus Hallicus LongusLongus

Tibialis Tibialis PosteriorPosterior

Peroneus Peroneus LongusLongus

Peroneus BrevisPeroneus BrevisPeroneuPeroneus Tertiuss Tertius

Intrinsic Foot Muscles

• 1st Layer (Superficial)– Abductor Hallicus– Flexor Digitorum Brevis– Abductor Digiti Minimi

• 2nd Layer– Quadratus Plantae – Lumbricales

Intrinsic Foot Muscles

• 3rd Layer– Adductor Hallicus– Flexor Hallicus Brevis– Flexor Digiti Minimi

Intrinsic Foot Muscles

• 4th Layer– Plantar Interosseous– Dorsal Interosseous

Intrinsic Foot Muscles

Foot loading

• Heel 60%• Forefoot 30%• Peak forefoot pressure under 2nd

MT• Footwear helps to distribute

pressures more evenly

Selecting Appropriate Footwear

• Footwear should be appropriate for existing structural deformities

• For pronators a rigid shoe is recommended

• For supinators require more flexible footwear with increased cushioning

• Midsole design also set to control motion along medial aspect of foot

• Heel counters are also used to control motion in the rearfoot

• Other aspects of shoes that may impact foot include outsole contour and composition, lacing systems and forefoot wedges

Selecting Appropriate Footwear