More than you ever wanted to know about the foot

MAJ Joel L. Shaw, US ArmySports Medicine

Overview

• Describe foot and ankle joints• Joint actions during running• Related pathology• How to prescribe running shoes

Foot function

• 1. Accept vertical forces during heel strike• 2. Absorb and dissipate these forces across

a flexible mid- and forefoot during pronation

• 3. Provide propulsion as the foot becomes a rigid lever with resupination and toe-off

Articulations

• Subtalar• Talocalcaneonavicular• Calcanealcuboid• Midtarsal• Tarsometatarsal• Metatarsophalangeal• Interphalangeal

Subtalar

• Triplanar – Supination vs. Pronation

• Bones: inferior talus, superior calcaneus• Alternating concave-convex facets limit

mobility• Ligaments- talocalcaneal, interosseous

talocalcaneal, cervical

Subtalar joint

• Supination– Inversion by calcaneus– Abduction by talus. – Dorsiflexion by talus

• Talar abduction causes external rotation of the tibia

• Position of most stability

Subtalar joint

• Pronation– Eversion by calcaneus– Adduction by talus– Plantarflexion by talus

• Talar adduction causes internal rotation of the tibia– May increase Q angle

• Increased flexibility and shock absorption

Subtalar joint

• Clinical significance– Mobility– Shock absorption– Stability

Midtarsal joint

• Functional joint- includes talonavicular and calcaneocuboid joint

• Triplanar supination/pronation- primarily DF/PF and abd/add

• Navicular- highest point of medial arch

Midtarsal joint

• Assist pronation/supination of the subtalar joint

• Maintain normal weight bearing forces on the forefoot

• Control/communication between rear foot and forefoot

Tarsometatarsal joint

• Connection from cuneiforms/cuboid to metatarsals

• Continue function of midtarsal joint• Positional regulation of metatarsals/

phalanges to the weight-bearing surface• Distributes body weight laterally• Pronate/supinate to keep forefoot on ground

Metatarsophalangeal joint

• Biplanar- mostly dorsiflexion/plantarflexion with 10 degrees of abduction/adduction

• Dorsiflexion- allows body to pass over foot while toes balance body weight during gait

• Plantarflexion- allows toes to press into ground for balance during gait

Metatarsophalangeal joint

• Metatarsal break– Oblique axis for flexion/extension passing

through 2nd to 5th metatarsal heads– Where foot hinges as the heel raises– Rigid lever during plantarflexion– Supination causes rearfoot/midfoot locking– Shifts body weight from medial to lateral

First ray

• Functional joint• Bones- Navicular, 1st Cuneiform, 1st

Metatarsal• Plantarflexion at late stance to assist 1st

MTP dorsiflexion• Peroneus longus and abductor hallicus

brevis muscles

Supporting soft tissues

• Plantar aponeurosis• Plantar arches• Ligaments

Plantar fascia

• Causes tension along the arch• Supination facilitated as arch heightened• Windlass effect

Windlass effect

• Webster’s: machine for pulling a rope around a drum. Pulley system to lift anchor in a boat.

Windlass effect

• Tension in the aponeurosis secondary to toe extension elevates the arch by acting as a pulley around which the aponeurosis is tightened.

Plantar arches

• Longitudinal arch– Shock absorption– Continuous medially and laterally– Bears most weight medially

• Transverse arch– Mobility– Extends from anterior tarsals to base of

metatarsals

Ligaments

• Spring ligament– Tension wire which helps maintain arch– Helps rigidity during propulsion

• Long plantar ligament• Plantar aponeurosis• Short plantar ligament

Function of arches

• Stability– Distribution of weight

• Mobility– Dampens shock of weight bearing– Adaptation to changes in support surfaces– Dampening of superimposed rotations

Running gait

• Stance phase– 40% of gait cycle– 2 phases

• Absorption• Propulsion

• Swing phase– 60% of gait cycle– 2 phases

• Initial swing (ISW)-75%

• Terminal swing (TSW)-25%

Running gait

• Double float• Stride length• Step length• Cadence

• Velocity=stride length x cadence

Running gait

• Kinematics vs. Kinetics– Kinematics- motion of joints independent of

forces that cause the motion to occur– Kinetics- study of forces that cause movement,

both internally and externally• Internal- muscle forces• External- ground reactive forces

Ankle/foot kinematics

• Ankle joint– Dorsiflexion/plantarflexion

• Foot joints– Triplanar– Pronation and supination

Running gait- ankle kinematics

• Absorption and midstance– Rapid dorsiflexion (response to increased hip

and knee flexion)– Decreased plantarflexion in runningà

decreased supinationàcause of increased running injuries??

Running gait- foot kinematics

• Subtalar motion determined by muscular activity and ground reactive forces

• Midtarsal motion determined by subtalar position

Running gait- midtarsal joint• Calcaneus/talus

supination– Increase midtarsal

obliquity– Lock joint– “Rigid lever”– During propulsion and

ISW

• Calcaneus/talus pronation– Parallel midtarsal

joints– Increased ROM– “Mobile adapter”– Mid stance

O'Connor FG, Wilder RP: Textbook of Running Medicine, McGraw Hill

Companies, 2001. Page 13.

Axis of transverse tarsal joint

Running gait- foot kinematics

• Absorption– Pelvis, femur, tibia internally rotate– Eversion and unlocking of subtalar joint– Pronation of midtarsal joints

• Allows mobility and shock absorption.• Able to adapt to ground surface.

– Plantar fascia- relax medial arch

Running gait- foot kinetics

• External forces- ground reactive forces– Vertical- 3-4 times body weight– Fore-aft- 30% of body weight– Medial-lateral- 10% of body weight– Newton’s third law

• Internal forces- muscle forces

External forces

• Foot strike pattern– Forefoot Midfoot Rearfoot

Rearfoot striker• 80% of runners• Initial contact- posterolateral foot• Center of Pressure (COP)

– Outer border of rear footàprogresses along lateral borderàthen across forefoot mediallyàtoward 1st and 2nd metatarsal head

Midfoot strikers

• Most other runners• Initial contact- midlateral border of foot• COP

– Lateral midfootàprogresses posteriorly (corresponds to heel contact)àrapidly moves to the medial forefoot

O'Connor FG, WilderRP: Textbook of Running Medicine, McGraw-Hill

Companies, 2001. Page 17

Center of Pressure

Evaluation of running injuries

• Training log• Shoe examination• Arch appraisal• Gait analysis• Running shoe

prescription

Training log

• Weekly mileage• Transition point• Increase in distance or intensity• Increase in mileage >10% per week• Change in terrain or running surface

Shoe examination

• Current running shoes– Age (days and miles)– Replacement frequency– New brand or model? (change biomechanics)

Shoe examination

• Outsole wear– Lateral heel vs. inside heel vs. lateral sole

• Midsole wear– Heel counter tilt– Midsole wrinkling, tilt, or decomposition

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Shoe wear

• Based on foot strike pattern, initial contact, and center of pressure

• Neutral gait– Wear on lateral aspect of heel– Uniform wear under the toes

Shoe wear

• Overpronator– Excessive wear on medial portion of heel and

forefoot• Underpronator

– Excessive wear on lateral heel– Wear on entire lateral portion of the outersole

Arch appraisal

• Standing arch contour

• “Wet test”• Static

evaluation=running evaluation?

Biomechanical function

• Required functions of locomotion– Adaptation– Shock absorption– Torque conversion– Stability– Rigidity

Biomechanical assessment

• Video gait analysis• Always base on running gait, not arch

height• Evaluate shoe wear

Gait analysis

• Behind- location of heel strike, foot motion during single stance, foot engaged at push-off

• Side- gastroc-soleus flexibility, great toe dorsiflexion

• Treadmill-based analysis• Force plate analysis

Neutral gait

• Level Heel Throughout Gait Cycle

• 90 Degree Medial Angle Throughout Gait Cycle

Intrinsic abnormalities

• Pes cavus- abnormal supination• Pes Planus- abnormal pronation

Supination

• Normal– Late stance phase– Provides rigidity,

support, propulsion– Facilitates lower leg

external rotation

• Abnormal– Minimal pronation at

subtalar joint– Little drop of medial

longitudinal arch

Abnormal supination- signs

• Lateral Leaning Foot Surface Placement

• Inflexible Foot• Callus- 1st and 5th

metatarsal heads• Clawing of 4th and 5th

digits

Abnormal supinators

• Stable and rigid foot• Lacks flexibility and

adaptability

• Poor gastroc-soleus flexibility– Achilles tendonitis– Plantar fasciitis

• Poor shock absorption– Tibial and femoral

stress fractures

Pronation

• Normal– Early in stance phase– Provides flexibility,

adaptability and shock absorption

– Facilitates lower leg internal rotation

• Abnormal– Continues throughout

stance phase

Mild Overpronation- signs

• Slightly Greater than 90 Degree Angle Throughout Gait Cycle

• Medial Leaning Foot Surface Placement

• Some Ankle Instability/ unstable position

Severe overpronation- signs

• Significant Medial Leaning of Surface Foot

• Great Instability• Excessive internal

tibial rotation• Increased medial

stress

Overpronators

• Patellofemoral pain• Popliteal tendonitis• Posterior tibial tendonitis• Achilles tendonitis• Plantar fasciitis• Metatarsal stress fracture

•

Arch Height Will Produce Different Levels of Flexibility

• Normal feet:– are flexible as they grip the ground and become stiff at

push off

• Flat feet:– are flexible as they grip the ground and remain flexible

at push off

• High arched feet– are inflexible and do not adjust to terrain well, but

provide a good base for push off.

Running Shoe Design• In an attempt to minimize injuries, running

shoes need to provide:– Cushioning

– Motion Control

– Support

Anatomyof the Running Shoe

Outersole

Uppers

Midsole

Midsole

Anatomy of the Running Shoe

Tongue

ToeboxLacing system

Heel notch

Heel counter

Anatomy of the Running Shoe

Flex GroovesFlex Grooves

Split HeelSplit Heel

Anatomy of the Running Shoe Last (Curvature)

Straight, Semi-curved and Curved

Anatomy of the Running Shoe

• Lasts (Shoe Template) – Board – Slip– Combination

• If you cannot remove insole, remove shoe…it is of poor quality

Shoe DesignMotion Control, Stability, Cushion

• Motion Control– Mod-Severe

overpronator • Stability

– majority of the population, slight overpronation

• Cushioned– Neutral/underpronator

runner

Stabilizing FeaturesSupport is added to

the inside or medial portion of the heel to counteract the foot rolling inward (pronation)

Running Shoe Selection

• The three basic types of running gait based on ankle biomechanics are: over-pronation, neutral and underpronation

• Shoes should be bought to accommodate your running gait, not your arch height!

Shoe prescription

• High arch- curve-lasted, cushion shoe

• Flat arch- motion control or stability shoes with firm midsoles and straight to semi-curved lasts

• Neutral arch- cushion or stability shoe

Orthotics

• Effectiveness– Gross, et al. 90% with symptom improvement– Schere. 81% with complete symptoms relief– Blake and Denton. Reduced pain associated

with plantar fasciitis by 80%.

Orthotics

• Motion control– Control excessive pronation

• Shock absorption• Pressure relief in specific area

– Plantar heel or great toe metatarsophalangeal• Redistribution of forces away from area

– Metatarsal pad for metatarsalgia/Morton’s neuroma

Orthotics

• Adjunct to rehab and training modification• Return athlete to full function• Prevent further injury• Functional orthoses

– Alter foot function– Guide foot through stance phase– Promote biomechanical efficiency

Orthotics

• Start with soft temporary orthotic• Over-the counter prefabricated devices

– Most athletes report improvement• Incomplete improvementàcustom orthotic

Pronated foot orthotic

• Flat medial arch• Unstable rearfoot and excessive motion of

plantar calcaneal fat pad• Weak plantarflexion of first metatarsal head

and weak “windlass” effect

Common mistakes

• Only looking at standing gait• Failure to evaluate various needs of

different runners• Need of different orthoses for running and

everyday activity

Summary

• Understand normal foot biomechanics-pronation vs. supination

• Evaluate with functional arch and shoe wear• Signs of abnormal arch• Match shoes and orthotics to running

alignment- correct shoes and over-the-counter inserts first

Questions??

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