More than you ever wanted to know about the foot MAJ Joel L. Shaw Sports Medicine 24 May 2007
Mar 28, 2015
More than you ever wanted to know about the foot
MAJ Joel L. Shaw
Sports Medicine
24 May 2007
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
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
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
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.
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 running
decreased supinationcause 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 kinematics
• Propulsion– Pelvis, femur, tibia externally rotate– Inversion/locking of subtalar joint– Supination of forefoot– Plantar fascia- increase medial arch stability
and invert heel– Metatarsal break- promote hindfoot inversion
and external rotation of leg
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 footprogresses along
lateral borderthen across forefoot medially toward 1st and 2nd metatarsal head
Midfoot strikers
• Most other runners
• Initial contact- midlateral border of foot
• COP– Lateral midfootprogresses posteriorly
(corresponds to heel contact)rapidly moves to the medial forefoot
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
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
Toebox
Lacing systemHeel 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
Stabilizing Features
Support 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 improvementcustom orthotic
High arch orthotic
• Dropped forefoot
• Plantarflexed first metatarsal and forefoot valgus
• Decreased subtalar range of motion
• Plantarflexed first ray, unstable cuboid
• Peroneal cuboid syndrome
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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